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Django In The Real World

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    Notes on slide 1

    Oh hai. I’m Jacob Kaplan-Moss; here’s a few ways to get in touch with me.

    I wear quite a few hats. Today, I’m wearing two: I’m one of the lead developers of Django; I’m a partner at `Revolution Systems`__, a consulting business specializing in, well, the stuff I’m about to talk about.

    Just a brief shameless plug: my day job is as a consultant working in and around these issues. I get to come talk about this stuff publicly because of this gig, so If you need info specific to your situation please consider giving us a call!

    Credit where credit is due: I first gave this talk at PyCon 2009 with the help of `James Bennett`__, so much of my thinking and some of the content comes from James.

    __ http://b-list.org/

    This is the main theme of this tutorial: you’ve written a Django site...

    ... and you’ve barely started.

    Writing the app is the easy part; what comes next is seriously complicated.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    Here’s just one list (Leonard Lin’s) of what you might need to think about *after* writing your app; I could easily add another dozen more things to this list. Luckily, not every site needs *all* of this... but any site of any size will need to understand at last some of this stuff, and bigger deployments will need to worry about all of it.

    Obviously this is far too much to cover even in a long tutorial, so we’ll pick and choose; the point is that writing the app is usually the easy part. Today we’re talking about what comes next.

    So here’s the bare minimum you’ll need to think about:

    * You need to test your sites. Without tests, you can’t move forward without downtime.
    * You need to write your code in a way that makes deployment possible — and easy.
    * You need to use deployment tools that automate the repetitive bits and keep you from shooting yourself in the foot.
    * You need a production environment that scales with your traffic.
    * You need to watch your sites in action so that you know what’s up.
    * When things go slow you need to fix it.

    So here’s the bare minimum you’ll need to think about:

    * You need to test your sites. Without tests, you can’t move forward without downtime.
    * You need to write your code in a way that makes deployment possible — and easy.
    * You need to use deployment tools that automate the repetitive bits and keep you from shooting yourself in the foot.
    * You need a production environment that scales with your traffic.
    * You need to watch your sites in action so that you know what’s up.
    * When things go slow you need to fix it.

    So here’s the bare minimum you’ll need to think about:

    * You need to test your sites. Without tests, you can’t move forward without downtime.
    * You need to write your code in a way that makes deployment possible — and easy.
    * You need to use deployment tools that automate the repetitive bits and keep you from shooting yourself in the foot.
    * You need a production environment that scales with your traffic.
    * You need to watch your sites in action so that you know what’s up.
    * When things go slow you need to fix it.

    So here’s the bare minimum you’ll need to think about:

    * You need to test your sites. Without tests, you can’t move forward without downtime.
    * You need to write your code in a way that makes deployment possible — and easy.
    * You need to use deployment tools that automate the repetitive bits and keep you from shooting yourself in the foot.
    * You need a production environment that scales with your traffic.
    * You need to watch your sites in action so that you know what’s up.
    * When things go slow you need to fix it.

    So here’s the bare minimum you’ll need to think about:

    * You need to test your sites. Without tests, you can’t move forward without downtime.
    * You need to write your code in a way that makes deployment possible — and easy.
    * You need to use deployment tools that automate the repetitive bits and keep you from shooting yourself in the foot.
    * You need a production environment that scales with your traffic.
    * You need to watch your sites in action so that you know what’s up.
    * When things go slow you need to fix it.

    So here’s the bare minimum you’ll need to think about:

    * You need to test your sites. Without tests, you can’t move forward without downtime.
    * You need to write your code in a way that makes deployment possible — and easy.
    * You need to use deployment tools that automate the repetitive bits and keep you from shooting yourself in the foot.
    * You need a production environment that scales with your traffic.
    * You need to watch your sites in action so that you know what’s up.
    * When things go slow you need to fix it.

    So now you’ve got a working app, but how do you *know* that it works? Sure, you could just run the site and click around, but that guarantees nothing. The difference between stable and unstable code is often the quality of the tests.

    The “fear” that Beck is talking about here is the fear of not knowing if your new site will run or not. Testing, while often boring, relives you of that fear.

    `Test Driven Development`__ by Kent Beck is the bible of TDD. Beck requires that you only add new code to your project after an existing test fails. This means writing tests before writing any new code. It can be rewarding -- particularly if you’re pair programming so you can keep each other honest. Unfortunately, it’s also simply not practical for most developers.

    __ http://www.amazon.com/dp/0321146530/

    This is the pragmatic approach to testing: write tests when you need them. If you need to chase down a bug, write a test to trigger the bug, then when the test passes you know the bug is licked.

    Yes, this leaves you with less than perfect coverage.

    I’m speaking from experience here. Once you commit with even a *single* breaking test, finding the time to clean up is an uphill battle. Knowing the suite fails discourages you from even running the tests at all, and thus the quality continues to decline.

    I tend to think of this as a continuum of testing; another way of thinking about this is a continuum between internal/external, or whitebox/blackbox.

    I tend to think of this as a continuum of testing; another way of thinking about this is a continuum between internal/external, or whitebox/blackbox.

    I tend to think of this as a continuum of testing; another way of thinking about this is a continuum between internal/external, or whitebox/blackbox.

    I tend to think of this as a continuum of testing; another way of thinking about this is a continuum between internal/external, or whitebox/blackbox.

    Testing web applications is *hard*. Anything with a persistent state -- i.e. a database -- and network communications -- HTTP -- is a real pain to test.

    Ruby on Rails really changed the game, though. When it shipped a set of tools that took most of the pain out of automating web tests, it galvenized developers to compete.

    Django’s since come out with our own spin on this set of tools. I’m only going to cover doctests in this intro tutorial, so a brief overview of the other tools is in order:

    * Unit tests: Django can run tests using Python’s standard `unittest` framework, which is based on Java’s JUnit. Perfect for more formal unit tests like you’d see in Java/C#.
    * Fixtures: fixtures are a way of loading preset data into the database for each test, thus letting you test against “real” data.
    * The test client: this lets you “fake” a request to your views and inspect the returned response, template, and context.
    * Email capture: the test suite will intercept sent email so you can test logic involving email.

    Testing web applications is *hard*. Anything with a persistent state -- i.e. a database -- and network communications -- HTTP -- is a real pain to test.

    Ruby on Rails really changed the game, though. When it shipped a set of tools that took most of the pain out of automating web tests, it galvenized developers to compete.

    Django’s since come out with our own spin on this set of tools. I’m only going to cover doctests in this intro tutorial, so a brief overview of the other tools is in order:

    * Unit tests: Django can run tests using Python’s standard `unittest` framework, which is based on Java’s JUnit. Perfect for more formal unit tests like you’d see in Java/C#.
    * Fixtures: fixtures are a way of loading preset data into the database for each test, thus letting you test against “real” data.
    * The test client: this lets you “fake” a request to your views and inspect the returned response, template, and context.
    * Email capture: the test suite will intercept sent email so you can test logic involving email.

    Testing web applications is *hard*. Anything with a persistent state -- i.e. a database -- and network communications -- HTTP -- is a real pain to test.

    Ruby on Rails really changed the game, though. When it shipped a set of tools that took most of the pain out of automating web tests, it galvenized developers to compete.

    Django’s since come out with our own spin on this set of tools. I’m only going to cover doctests in this intro tutorial, so a brief overview of the other tools is in order:

    * Unit tests: Django can run tests using Python’s standard `unittest` framework, which is based on Java’s JUnit. Perfect for more formal unit tests like you’d see in Java/C#.
    * Fixtures: fixtures are a way of loading preset data into the database for each test, thus letting you test against “real” data.
    * The test client: this lets you “fake” a request to your views and inspect the returned response, template, and context.
    * Email capture: the test suite will intercept sent email so you can test logic involving email.

    Testing web applications is *hard*. Anything with a persistent state -- i.e. a database -- and network communications -- HTTP -- is a real pain to test.

    Ruby on Rails really changed the game, though. When it shipped a set of tools that took most of the pain out of automating web tests, it galvenized developers to compete.

    Django’s since come out with our own spin on this set of tools. I’m only going to cover doctests in this intro tutorial, so a brief overview of the other tools is in order:

    * Unit tests: Django can run tests using Python’s standard `unittest` framework, which is based on Java’s JUnit. Perfect for more formal unit tests like you’d see in Java/C#.
    * Fixtures: fixtures are a way of loading preset data into the database for each test, thus letting you test against “real” data.
    * The test client: this lets you “fake” a request to your views and inspect the returned response, template, and context.
    * Email capture: the test suite will intercept sent email so you can test logic involving email.

    Testing web applications is *hard*. Anything with a persistent state -- i.e. a database -- and network communications -- HTTP -- is a real pain to test.

    Ruby on Rails really changed the game, though. When it shipped a set of tools that took most of the pain out of automating web tests, it galvenized developers to compete.

    Django’s since come out with our own spin on this set of tools. I’m only going to cover doctests in this intro tutorial, so a brief overview of the other tools is in order:

    * Unit tests: Django can run tests using Python’s standard `unittest` framework, which is based on Java’s JUnit. Perfect for more formal unit tests like you’d see in Java/C#.
    * Fixtures: fixtures are a way of loading preset data into the database for each test, thus letting you test against “real” data.
    * The test client: this lets you “fake” a request to your views and inspect the returned response, template, and context.
    * Email capture: the test suite will intercept sent email so you can test logic involving email.

    22 Favorites

    Django In The Real World - Presentation Transcript

    1. Django in the Real World Jacob Kaplan-Moss OSCON 2009 http://jacobian.org/TN
    2. Jacob Kaplan-Moss http://jacobian.org / jacob@jacobian.org / @jacobian Lead Developer, Django Partner, Revolution Systems 2
    3. Shameless plug: http://revsys.com/ 3
    4. Hat tip: James Bennett (http://b-list.org) 4
    5. So you’ve written a Django site… 5
    6. … now what? 6
    7. http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    8. • API Metering http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    9. • API Metering • Backups & Snapshots http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    10. • API Metering • Backups & Snapshots • Counters http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    11. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    12. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    13. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    14. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    15. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    16. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    17. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    18. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    19. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    20. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    21. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    22. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    23. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    24. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    25. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    26. • API Metering • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    27. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    28. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    29. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    30. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    31. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    32. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    33. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    34. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    35. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    36. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    37. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Real-time messaging (XMPP) • Multiple Devs, Staging, Prod • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    38. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Real-time messaging (XMPP) • Multiple Devs, Staging, Prod • Search • Data model upgrades • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    39. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Real-time messaging (XMPP) • Multiple Devs, Staging, Prod • Search • Data model upgrades • Ranging • Rolling deployments • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    40. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Real-time messaging (XMPP) • Multiple Devs, Staging, Prod • Search • Data model upgrades • Ranging • Rolling deployments • Geo • Multiple versions (selective beta) • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    41. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Real-time messaging (XMPP) • Multiple Devs, Staging, Prod • Search • Data model upgrades • Ranging • Rolling deployments • Geo • Multiple versions (selective beta) • Sharding • Bucket Testing • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    42. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Real-time messaging (XMPP) • Multiple Devs, Staging, Prod • Search • Data model upgrades • Ranging • Rolling deployments • Geo • Multiple versions (selective beta) • Sharding • Bucket Testing • Smart Caching • Rollbacks • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    43. • API Metering • Distributed Log storage, analysis • Backups & Snapshots • Graphing • Counters • HTTP Caching • Cloud/Cluster Management Tools • Input/Output Filtering • Instrumentation/Monitoring • Memory Caching • Failover • Non-relational Key Stores • Node addition/removal and hashing • Rate Limiting • Auto-scaling for cloud resources • Relational Storage • CSRF/XSS Protection • Queues • Data Retention/Archival • Rate Limiting • Deployment Tools • Real-time messaging (XMPP) • Multiple Devs, Staging, Prod • Search • Data model upgrades • Ranging • Rolling deployments • Geo • Multiple versions (selective beta) • Sharding • Bucket Testing • Smart Caching • Rollbacks • Dirty-table management • CDN Management • Distributed File Storage http://randomfoo.net/2009/01/28/infrastructure-for-modern-web-sites 7
    44. The bare minimum: 8
    45. The bare minimum: • Test. 8
    46. The bare minimum: • Test. • Structure for deployment. 8
    47. The bare minimum: • Test. • Structure for deployment. • Use deployment tools. 8
    48. The bare minimum: • Test. • Structure for deployment. • Use deployment tools. • Design a production environment. 8
    49. The bare minimum: • Test. • Structure for deployment. • Use deployment tools. • Design a production environment. • Monitor. 8
    50. The bare minimum: • Test. • Structure for deployment. • Use deployment tools. • Design a production environment. • Monitor. • Tune. 8
    51. Testing 9
    52. “ Tests are the Programmer’s stone, transmuting fear into ” boredom. — Kent Beck 10
    53. Hardcore TDD 11
    54. “ I don’t do test driven development. I do stupidity driven testing… I wait until I do something stupid, and ” then write tests to avoid doing it again. — Titus Brown 12
    55. Whatever happens, don’t let your test suite break thinking, “I’ll go back and fix this later.” 13
    56. Unit testing Functional/behavior testing Browser testing 14
    57. Unit testing unittest Functional/behavior testing Browser testing 14
    58. Unit testing unittest doctest Functional/behavior testing Browser testing 14
    59. Unit testing unittest doctest Functional/behavior testing django.test.Client, Twill Browser testing 14
    60. Unit testing unittest doctest Functional/behavior testing django.test.Client, Twill Browser testing Windmill, Selenium 14
    61. You need them all. 15
    62. Testing Django 16
    63. Testing Django • Unit tests (unittest) 16
    64. Testing Django • Unit tests (unittest) • Doctests (doctest) 16
    65. Testing Django • Unit tests (unittest) • Doctests (doctest) • Fixtures 16
    66. Testing Django • Unit tests (unittest) • Doctests (doctest) • Fixtures • Test client 16
    67. Testing Django • Unit tests (unittest) • Doctests (doctest) • Fixtures • Test client • Email capture 16
    68. Unit tests 17
    69. Unit tests • “Whitebox” testing 17
    70. Unit tests • “Whitebox” testing • Verify the small functional units of your app 17
    71. Unit tests • “Whitebox” testing • Verify the small functional units of your app • Very fine-grained 17
    72. Unit tests • “Whitebox” testing • Verify the small functional units of your app • Very fine-grained • Familier to most programmers (JUnit, NUnit, etc.) 17
    73. Unit tests • “Whitebox” testing • Verify the small functional units of your app • Very fine-grained • Familier to most programmers (JUnit, NUnit, etc.) • Provided in Python by unittest 17
    74. django.test.TestCase 18
    75. django.test.TestCase • Fixtures. 18
    76. django.test.TestCase • Fixtures. • Test client. 18
    77. django.test.TestCase • Fixtures. • Test client. • Email capture. 18
    78. django.test.TestCase • Fixtures. • Test client. • Email capture. • Database management. 18
    79. django.test.TestCase • Fixtures. • Test client. • Email capture. • Database management. • Slower than unittest.TestCase. 18
    80. class StoryAddViewTests(TestCase): fixtures = ['authtestdata', 'newsbudget_test_data'] urls = 'newsbudget.urls' def test_story_add_get(self): r = self.client.get('/budget/stories/add/') self.assertEqual(r.status_code, 200) … def test_story_add_post(self): data = { 'title': 'Hungry cat is hungry', 'date': '2009-01-01', } r = self.client.post('/budget/stories/add/', data) self.assertEqual(r.status_code, 302) … 19
    81. Doctests 20
    82. Doctests • Easy to write & read. 20
    83. Doctests • Easy to write & read. • Produces self-documenting code. 20
    84. Doctests • Easy to write & read. • Produces self-documenting code. • Great for cases that only use assertEquals. 20
    85. Doctests • Easy to write & read. • Produces self-documenting code. • Great for cases that only use assertEquals. • Somewhere between unit tests and functional tests. 20
    86. Doctests • Easy to write & read. • Produces self-documenting code. • Great for cases that only use assertEquals. • Somewhere between unit tests and functional tests. • Difficult to debug. 20
    87. Doctests • Easy to write & read. • Produces self-documenting code. • Great for cases that only use assertEquals. • Somewhere between unit tests and functional tests. • Difficult to debug. • Don’t always provide useful test failures. 20
    88. class Choices(object): """ Easy declarative "choices" tool:: >>> STATUSES = Choices("Live", "Draft") # Acts like a choices list: >>> list(STATUSES) [(1, 'Live'), (2, 'Draft')] # Easily convert from code to verbose: >>> STATUSES.verbose(1) 'Live' # ... and vice versa: >>> STATUSES.code("Draft") 2 """ … 21
    89. **************************************************** File "utils.py", line 150, in __main__.Choices Failed example: STATUSES.verbose(1) Expected: 'Live' Got: 'Draft' **************************************************** 22
    90. Functional tests 23
    91. Functional tests • a.k.a “Behavior Driven Development.” 23
    92. Functional tests • a.k.a “Behavior Driven Development.” • “Blackbox,” holistic testing. 23
    93. Functional tests • a.k.a “Behavior Driven Development.” • “Blackbox,” holistic testing. • All the hardcore TDD folks look down on functional tests. 23
    94. Functional tests • a.k.a “Behavior Driven Development.” • “Blackbox,” holistic testing. • All the hardcore TDD folks look down on functional tests. • But they keep your boss happy. 23
    95. Functional tests • a.k.a “Behavior Driven Development.” • “Blackbox,” holistic testing. • All the hardcore TDD folks look down on functional tests. • But they keep your boss happy. • Easy to find problems; harder to find the actual bug. 23
    96. Functional testing tools 24
    97. Functional testing tools • django.test.Client 24
    98. Functional testing tools • django.test.Client • webunit 24
    99. Functional testing tools • django.test.Client • webunit • Twill 24
    100. Functional testing tools • django.test.Client • webunit • Twill • ... 24
    101. django.test.Client 25
    102. django.test.Client • Test the whole request path without running a web server. 25
    103. django.test.Client • Test the whole request path without running a web server. • Responses provide extra information about templates and their contexts. 25
    104. class StoryAddViewTests(TestCase): fixtures = ['authtestdata', 'newsbudget_test_data'] urls = 'newsbudget.urls' def test_story_add_get(self): r = self.client.get('/budget/stories/add/') self.assertEqual(r.status_code, 200) … def test_story_add_post(self): data = { 'title': 'Hungry cat is hungry', 'date': '2009-01-01', } r = self.client.post('/budget/stories/add/', data) self.assertEqual(r.status_code, 302) … 26
    105. Web browser testing 27
    106. Web browser testing • The ultimate in functional testing for web applications. 27
    107. Web browser testing • The ultimate in functional testing for web applications. • Run test in a web browser. 27
    108. Web browser testing • The ultimate in functional testing for web applications. • Run test in a web browser. • Can verify JavaScript, AJAX; even CSS. 27
    109. Web browser testing • The ultimate in functional testing for web applications. • Run test in a web browser. • Can verify JavaScript, AJAX; even CSS. • Test your site across supported browsers. 27
    110. Browser testing tools 28
    111. Browser testing tools • Selenium 28
    112. Browser testing tools • Selenium • Windmill 28
    113. “Exotic” testing 29
    114. “Exotic” testing • Static source analysis. 29
    115. “Exotic” testing • Static source analysis. • Smoke testing (crawlers and spiders). 29
    116. “Exotic” testing • Static source analysis. • Smoke testing (crawlers and spiders). • Monkey testing. 29
    117. “Exotic” testing • Static source analysis. • Smoke testing (crawlers and spiders). • Monkey testing. • Load testing. 29
    118. “Exotic” testing • Static source analysis. • Smoke testing (crawlers and spiders). • Monkey testing. • Load testing. • ... 29
    119. 30
    120. Further resources 31
    121. Further resources • Windmill talk here at OSCON http://bit.ly/14tkrd 31
    122. Further resources • Windmill talk here at OSCON http://bit.ly/14tkrd • Django testing documentation http://bit.ly/django-testing 31
    123. Further resources • Windmill talk here at OSCON http://bit.ly/14tkrd • Django testing documentation http://bit.ly/django-testing • Python Testing Tools Taxonomy http://bit.ly/py-testing-tools 31
    124. Structuring applications for reuse 32
    125. Designing for reuse 33
    126. Designing for reuse • Do one thing, and do it well. 33
    127. Designing for reuse • Do one thing, and do it well. • Don’t be afraid of multiple apps. 33
    128. Designing for reuse • Do one thing, and do it well. • Don’t be afraid of multiple apps. • Write for flexibility. 33
    129. Designing for reuse • Do one thing, and do it well. • Don’t be afraid of multiple apps. • Write for flexibility. • Build to distribute. 33
    130. Designing for reuse • Do one thing, and do it well. • Don’t be afraid of multiple apps. • Write for flexibility. • Build to distribute. • Extend carefully. 33
    131. 1. Do one thing, and do it well. 34
    132. Application == encapsulation 35
    133. Focus 36
    134. Focus • Ask yourself: “What does this application do?” 36
    135. Focus • Ask yourself: “What does this application do?” • Answer should be one or two short sentences. 36
    136. Good focus 37
    137. Good focus • “Handle storage of users and authentication of their identities.” 37
    138. Good focus • “Handle storage of users and authentication of their identities.” • “Allow content to be tagged, del.icio.us style, with querying by tags.” 37
    139. Good focus • “Handle storage of users and authentication of their identities.” • “Allow content to be tagged, del.icio.us style, with querying by tags.” • “Handle entries in a weblog.” 37
    140. Bad focus 38
    141. Bad focus • “Handle entries in a weblog, and users who post them, and their authentication, and tagging and categorization, and some flat pages for static content, and...” 38
    142. Warning signs 39
    143. Warning signs • Lots of files. 39
    144. Warning signs • Lots of files. • Lots of modules. 39
    145. Warning signs • Lots of files. • Lots of modules. • Lots of models. 39
    146. Warning signs • Lots of files. • Lots of modules. • Lots of models. • Lots of code. 39
    147. Small is good 40
    148. Small is good • Many great Django apps are very small. 40
    149. Small is good • Many great Django apps are very small. • Even a lot of “simple” Django sites commonly have a dozen or more applications in INSTALLED_APPS. 40
    150. Small is good • Many great Django apps are very small. • Even a lot of “simple” Django sites commonly have a dozen or more applications in INSTALLED_APPS. • If you’ve got a complex site and a short application list, something’s probably wrong. 40
    151. Approach features skeptically 41
    152. Approach features skeptically • What does the application do? 41
    153. Approach features skeptically • What does the application do? • Does this feature have anything to do with that? 41
    154. Approach features skeptically • What does the application do? • Does this feature have anything to do with that? • No? Don’t add it. 41
    155. 2. Don’t be afraid of many apps. 42
    156. The monolith anti-pattern 43
    157. The monolith anti-pattern • The “application” is the whole site. 43
    158. The monolith anti-pattern • The “application” is the whole site. • Re-use? YAGNI. 43
    159. The monolith anti-pattern • The “application” is the whole site. • Re-use? YAGNI. • Plugins that hook into the “main” application. 43
    160. The monolith anti-pattern • The “application” is the whole site. • Re-use? YAGNI. • Plugins that hook into the “main” application. • Heavy use of middleware-like concepts. 43
    161. (I blame Rails) 44
    162. The Django mindset 45
    163. The Django mindset • Application: some bit of functionality. 45
    164. The Django mindset • Application: some bit of functionality. • Site: several applications. 45
    165. The Django mindset • Application: some bit of functionality. • Site: several applications. • Spin off new “apps” liberally. 45
    166. The Django mindset • Application: some bit of functionality. • Site: several applications. • Spin off new “apps” liberally. • Develop a suite of apps ready for when they’re needed. 45
    167. Django encourages this 46
    168. Django encourages this • INSTALLED_APPS 46
    169. Django encourages this • INSTALLED_APPS • Applications are just Python packages, not some Django-specific “app” or “plugin.” 46
    170. Django encourages this • INSTALLED_APPS • Applications are just Python packages, not some Django-specific “app” or “plugin.” • Abstractions like django.contrib.sites make you think about this as you develop. 46
    171. Spin off a new app? 47
    172. Spin off a new app? • Is this feature unrelated to the app’s focus? 47
    173. Spin off a new app? • Is this feature unrelated to the app’s focus? • Is it orthogonal to the rest of the app? 47
    174. Spin off a new app? • Is this feature unrelated to the app’s focus? • Is it orthogonal to the rest of the app? • Will I need similar functionality again? 47
    175. The ideal: 48
    176. I need a contact form 49
    177. urlpatterns = ('', … (r'^contact/', include('contact_form.urls')), … ) 50
    178. Done. (http://bitbucket.org/ubernostrum/django-contact-form/) 51
    179. But… what about… 52
    180. But… what about… • Site A wants a contact form that just collects a message. 52
    181. But… what about… • Site A wants a contact form that just collects a message. • Site B’s marketing department wants a bunch of info. 52
    182. But… what about… • Site A wants a contact form that just collects a message. • Site B’s marketing department wants a bunch of info. • Site C wants to use Akismet to filter automated spam. 52
    183. 53
    184. 53
    185. 3. Write for flexibility. 54
    186. Common sense 55
    187. Common sense • Sane defaults. 55
    188. Common sense • Sane defaults. • Easy overrides. 55
    189. Common sense • Sane defaults. • Easy overrides. • Don’t set anything in stone. 55
    190. Forms 56
    191. Forms • Supply a form class. 56
    192. Forms • Supply a form class. • Let users specify their own. 56
    193. Templates 57
    194. Templates • Specify a default template. 57
    195. Templates • Specify a default template. • Let users specify their own. 57
    196. Form processing 58
    197. Form processing • You want to redirect after successful submission. 58
    198. Form processing • You want to redirect after successful submission. • Supply a default URL. 58
    199. Form processing • You want to redirect after successful submission. • Supply a default URL. • (Preferably by using reverse resolution). 58
    200. Form processing • You want to redirect after successful submission. • Supply a default URL. • (Preferably by using reverse resolution). • Let users override the default. 58
    201. def edit_entry(request, entry_id): form = EntryForm(request.POST or None) if form.is_valid(): form.save() return redirect('entry_detail', entry_id) return render_to_response('entry/form.html', {…}) 59
    202. def edit_entry(request, entry_id, form_class=EntryForm, template_name='entry/form.html', post_save_redirect=None): form = form_class(request.POST or None) if form.is_valid(): form.save() if post_save_redirect: return redirect(post_save_redirect) else: return redirect('entry_detail', entry_id) return render_to_response([template_name, 'entry/form.html'], {…}) 60
    203. URLs 61
    204. URLs • Provide a URLConf with all views. 61
    205. URLs • Provide a URLConf with all views. • Use named URL patterns. 61
    206. URLs • Provide a URLConf with all views. • Use named URL patterns. • Use reverse lookups (by name). 61
    207. 4. Build to distribute (even private code). 62
    208. What the tutorial teaches myproject/ settings.py urls.py myapp/ models.py mysecondapp/ views.py … 63
    209. from myproject.myapp.models import … from myproject. myapp.models import … … myproject.settings myproject.urls 64
    210. Project coupling kills re-use 65
    211. Projects in real life. 66
    212. Projects in real life. • A settings module. 66
    213. Projects in real life. • A settings module. • A root URLConf. 66
    214. Projects in real life. • A settings module. • A root URLConf. • Maybe a manage.py (but…) 66
    215. Projects in real life. • A settings module. • A root URLConf. • Maybe a manage.py (but…) • And that’s it. 66
    216. Advantages 67
    217. Advantages • No assumptions about where things live. 67
    218. Advantages • No assumptions about where things live. • No PYTHONPATH magic. 67
    219. Advantages • No assumptions about where things live. • No PYTHONPATH magic. • Reminds you that “projects” are just a Python module. 67
    220. You don’t even need a project 68
    221. ljworld.com: 69
    222. ljworld.com: • worldonline.settings.ljworld 69
    223. ljworld.com: • worldonline.settings.ljworld • worldonline.urls.ljworld 69
    224. ljworld.com: • worldonline.settings.ljworld • worldonline.urls.ljworld • And a whole bunch of apps. 69
    225. Where apps really live 70
    226. Where apps really live • Single module directly on Python path (registration, tagging, etc.). 70
    227. Where apps really live • Single module directly on Python path (registration, tagging, etc.). • Related modules under a top-level package (ellington.events, ellington.podcasts, etc.) 70
    228. Where apps really live • Single module directly on Python path (registration, tagging, etc.). • Related modules under a top-level package (ellington.events, ellington.podcasts, etc.) • No projects (ellington.settings doesn’t exist). 70
    229. Want to distribute? 71
    230. Want to distribute? • Build a package with distutils/setuptools. 71
    231. Want to distribute? • Build a package with distutils/setuptools. • Put it on PyPI (or a private package server). 71
    232. Want to distribute? • Build a package with distutils/setuptools. • Put it on PyPI (or a private package server). • Now it works with easy_install, pip, buildout, … 71
    233. General best practices 72
    234. General best practices • Establish dependancy rules. 72
    235. General best practices • Establish dependancy rules. • Establish a minimum Python version (suggestion: Python 2.5). 72
    236. General best practices • Establish dependancy rules. • Establish a minimum Python version (suggestion: Python 2.5). • Establish a minimum Django version (suggestion: Django 1.0). 72
    237. General best practices • Establish dependancy rules. • Establish a minimum Python version (suggestion: Python 2.5). • Establish a minimum Django version (suggestion: Django 1.0). • Test frequently against new versions of dependancies. 72
    238. Document obsessively. 73
    239. 5. Embrace and extend. 74
    240. Don’t touch! 75
    241. Don’t touch! • Good applications are extensible without patching. 75
    242. Don’t touch! • Good applications are extensible without patching. • Take advantage of every extensibility point an application gives you. 75
    243. Don’t touch! • Good applications are extensible without patching. • Take advantage of every extensibility point an application gives you. • You may end up doing something that deserves a new application anyway. 75
    244. But this application wasn’t meant to be extended! 76
    245. Python Power! 77
    246. Extending a view 78
    247. Extending a view • Wrap the view with your own code. 78
    248. Extending a view • Wrap the view with your own code. • Doing it repetitively? Write a decorator. 78
    249. Extending a model 79
    250. Extending a model • Relate other models to it. 79
    251. Extending a model • Relate other models to it. • Subclass it. 79
    252. Extending a model • Relate other models to it. • Subclass it. • Proxy subclasses (Django 1.1). 79
    253. Extending a form 80
    254. Extending a form • Subclass it. 80
    255. Extending a form • Subclass it. • There is no step 2. 80
    256. Other tricks 81
    257. Other tricks • Signals lets you fire off customized behavior when certain events happen. 81
    258. Other tricks • Signals lets you fire off customized behavior when certain events happen. • Middleware offers full control over request/response handling. 81
    259. Other tricks • Signals lets you fire off customized behavior when certain events happen. • Middleware offers full control over request/response handling. • Context processors can make additional information available if a view doesn’t. 81
    260. If you must make changes to external code… 82
    261. Keep changes to a minimum 83
    262. Keep changes to a minimum • If possible, instead of adding a feature, add extensibility. 83
    263. Keep changes to a minimum • If possible, instead of adding a feature, add extensibility. • Keep as much changed code as you can out of the original app. 83
    264. Stay up-to-date 84
    265. Stay up-to-date • Don’t want to get out of sync with the original version of the code! 84
    266. Stay up-to-date • Don’t want to get out of sync with the original version of the code! • You might miss bugfixes. 84
    267. Stay up-to-date • Don’t want to get out of sync with the original version of the code! • You might miss bugfixes. • You might even miss the feature you needed. 84
    268. Use a good VCS 85
    269. Use a good VCS • Subversion vendor branches don’t cut it. 85
    270. Use a good VCS • Subversion vendor branches don’t cut it. • DVCSes are perfect for this: 85
    271. Use a good VCS • Subversion vendor branches don’t cut it. • DVCSes are perfect for this: • Mercurial queues. 85
    272. Use a good VCS • Subversion vendor branches don’t cut it. • DVCSes are perfect for this: • Mercurial queues. • Git rebasing. 85
    273. Use a good VCS • Subversion vendor branches don’t cut it. • DVCSes are perfect for this: • Mercurial queues. • Git rebasing. • At the very least, maintain a patch queue by hand. 85
    274. Be a good citizen 86
    275. Be a good citizen • If you change someone else’s code, let them know. 86
    276. Be a good citizen • If you change someone else’s code, let them know. • Maybe they’ll merge your changes in and you won’t have to fork anymore. 86
    277. Further reading 87
    278. Deployment 88
    279. Deployment should... 89
    280. Deployment should... • Be automated. 89
    281. Deployment should... • Be automated. • Automatically manage dependencies. 89
    282. Deployment should... • Be automated. • Automatically manage dependencies. • Be isolated. 89
    283. Deployment should... • Be automated. • Automatically manage dependencies. • Be isolated. • Be repeatable. 89
    284. Deployment should... • Be automated. • Automatically manage dependencies. • Be isolated. • Be repeatable. • Be identical in staging and in production. 89
    285. Deployment should... • Be automated. • Automatically manage dependencies. • Be isolated. • Be repeatable. • Be identical in staging and in production. • Work the same for everyone. 89
    286. Dependency Isolation Automation management 90
    287. Dependency Isolation Automation management 90
    288. Dependency Isolation Automation management apt/yum/... virtualenv Capistrano easy_install zc.buildout Fabric pip Puppet/Chef/… zc.buildout 90
    289. Dependency Isolation Automation management apt/yum/... virtualenv Capistrano easy_install zc.buildout Fabric pip Puppet/Chef/… zc.buildout 90
    290. Dependency Isolation Automation management apt/yum/... virtualenv Capistrano easy_install zc.buildout Fabric pip Puppet/Chef/… zc.buildout 90
    291. Dependancy management 91
    292. Dependancy management • The Python ecosystem rocks! 91
    293. Dependancy management • The Python ecosystem rocks! • Python package management doesn’t. 91
    294. Dependancy management • The Python ecosystem rocks! • Python package management doesn’t. • Installing packages — and dependancies — correctly is a lot harder than it should be; most defaults are wrong. 91
    295. Dependancy management • The Python ecosystem rocks! • Python package management doesn’t. • Installing packages — and dependancies — correctly is a lot harder than it should be; most defaults are wrong. • Here be dragons. 91
    296. Vendor packages 92
    297. Vendor packages • APT, Yum, … 92
    298. Vendor packages • APT, Yum, … • The good: familiar tools; stability; handles dependancies not on PyPI. 92
    299. Vendor packages • APT, Yum, … • The good: familiar tools; stability; handles dependancies not on PyPI. • The bad: small selection; not (very) portable; hard to supply user packages. 92
    300. Vendor packages • APT, Yum, … • The good: familiar tools; stability; handles dependancies not on PyPI. • The bad: small selection; not (very) portable; hard to supply user packages. • The ugly: installs packages system-wide. 92
    301. easy_install 93
    302. easy_install • The good: multi-version packages. 93
    303. easy_install • The good: multi-version packages. • The bad: requires ‘net connection; can’t uninstall; can’t handle non-PyPI packages; multi-version packages barely work. 93
    304. easy_install • The good: multi-version packages. • The bad: requires ‘net connection; can’t uninstall; can’t handle non-PyPI packages; multi-version packages barely work. • The ugly: stale; unsupported; defaults almost totally wrong; installs system-wide. 93
    305. pip http://pip.openplans.org/ 94
    306. pip http://pip.openplans.org/ • “Pip Installs Packages” 94
    307. pip http://pip.openplans.org/ • “Pip Installs Packages” • The good: Just Works™; handles non- PyPI packages (including direct from SCM); repeatable dependancies; integrates with virtualenv for isolation. 94
    308. pip http://pip.openplans.org/ • “Pip Installs Packages” • The good: Just Works™; handles non- PyPI packages (including direct from SCM); repeatable dependancies; integrates with virtualenv for isolation. • The bad: still young; not yet bundled. 94
    309. pip http://pip.openplans.org/ • “Pip Installs Packages” • The good: Just Works™; handles non- PyPI packages (including direct from SCM); repeatable dependancies; integrates with virtualenv for isolation. • The bad: still young; not yet bundled. • The ugly: haven’t found it yet. 94
    310. zc.buildout http://buildout.org/ 95
    311. zc.buildout http://buildout.org/ • The good: incredibly flexible; handles any sort of dependancy; repeatable builds; reusable “recipes;” good ecosystem; handles isolation, too. 95
    312. zc.buildout http://buildout.org/ • The good: incredibly flexible; handles any sort of dependancy; repeatable builds; reusable “recipes;” good ecosystem; handles isolation, too. • The bad: often cryptic, INI-style configuration file; confusing duplication of recipes; sometimes too flexible. 95
    313. zc.buildout http://buildout.org/ • The good: incredibly flexible; handles any sort of dependancy; repeatable builds; reusable “recipes;” good ecosystem; handles isolation, too. • The bad: often cryptic, INI-style configuration file; confusing duplication of recipes; sometimes too flexible. • The ugly: nearly completely undocumented. 95
    314. Package isolation 96
    315. Package isolation • Why? 96
    316. Package isolation • Why? • Site A requires Foo v1.0; site B requires Foo v2.0. 96
    317. Package isolation • Why? • Site A requires Foo v1.0; site B requires Foo v2.0. • You need to develop against multiple versions of dependancies. 96
    318. Package isolation tools 97
    319. Package isolation tools • Virtual machines (Xen, VMWare, EC2, …) 97
    320. Package isolation tools • Virtual machines (Xen, VMWare, EC2, …) • Multiple Python installations. 97
    321. Package isolation tools • Virtual machines (Xen, VMWare, EC2, …) • Multiple Python installations. • “Virtual” Python installations. 97
    322. Package isolation tools • Virtual machines (Xen, VMWare, EC2, …) • Multiple Python installations. • “Virtual” Python installations. • virtualenv http://pypi.python.org/pypi/virtualenv 97
    323. Package isolation tools • Virtual machines (Xen, VMWare, EC2, …) • Multiple Python installations. • “Virtual” Python installations. • virtualenv http://pypi.python.org/pypi/virtualenv • zc.buildout http://buildout.org/ 97
    324. Why automate? 98
    325. Why automate? • “I can’t push this fix to the servers until Alex gets back from lunch.” 98
    326. Why automate? • “I can’t push this fix to the servers until Alex gets back from lunch.” • “Sorry, I can’t fix that. I’m new here.” 98
    327. Why automate? • “I can’t push this fix to the servers until Alex gets back from lunch.” • “Sorry, I can’t fix that. I’m new here.” • “Oops, I just made the wrong version of our site live.” 98
    328. Why automate? • “I can’t push this fix to the servers until Alex gets back from lunch.” • “Sorry, I can’t fix that. I’m new here.” • “Oops, I just made the wrong version of our site live.” • “It’s broken! What’d you do!?” 98
    329. Automation basics 99
    330. Automation basics • SSH is right out. 99
    331. Automation basics • SSH is right out. • Don’t futz with the server. Write a recipe. 99
    332. Automation basics • SSH is right out. • Don’t futz with the server. Write a recipe. • Deploys should be idempotent. 99
    333. Capistrano http://capify.org/ 100
    334. Capistrano http://capify.org/ • The good: lots of features; good documentation; active community. 100
    335. Capistrano http://capify.org/ • The good: lots of features; good documentation; active community. • The bad: stale development; very “opinionated” and Rails-oriented. 100
    336. Fabric http://fabfile.org/ 101
    337. Fabric http://fabfile.org/ • The good: very simple; flexible; actively developed; Python. 101
    338. Fabric http://fabfile.org/ • The good: very simple; flexible; actively developed; Python. • The bad: no high-level commands; in flux. 101
    339. Configuration management 102
    340. Configuration management • CFEngine, Puppet, Chef, … 102
    341. Configuration management • CFEngine, Puppet, Chef, … • Will handle a lot more than code deployment! 102
    342. Configuration management • CFEngine, Puppet, Chef, … • Will handle a lot more than code deployment! • I only know a little about these. 102
    343. Recommendations Pip, Virtualenv, and Fabric Buildout and Fabric. Buildout and Puppet/Chef/…. Utility computing and Puppet/Chef/…. 103
    344. Production environments 104
    345. net. LiveJournal Backend: Today (Roughly.) BIG-IP perlbal (httpd/proxy) Global Database bigip1 mod_perl bigip2 proxy1 master_a master_b web1 proxy2 web2 proxy3 web3 Memcached slave1 slave2 ... slave5 djabberd proxy4 mc1 web4 djabberd proxy5 ... mc2 User DB Cluster 1 djabberd webN mc3 uc1a uc1b mc4 User DB Cluster 2 ... uc2a uc2b gearmand Mogile Storage Nodes gearmand1 mcN User DB Cluster 3 sto1 sto2 gearmandN uc3a uc3b Mogile Trackers ... sto8 tracker1 tracker3 User DB Cluster N ucNa ucNb MogileFS Database “workers” gearwrkN Job Queues (xN) mog_a mog_b theschwkN jqNa jqNb slave1 slaveN http://danga.com/words/ Brad Fitzpatrik, http://danga.com/words/2007_06_usenix/ 3 105
    346. django database media server 106
    347. Application servers 107
    348. Application servers • Apache + mod_python 107
    349. Application servers • Apache + mod_python • Apache + mod_wsgi 107
    350. Application servers • Apache + mod_python • Apache + mod_wsgi • Apache/lighttpd + FastCGI 107
    351. Application servers • Apache + mod_python • Apache + mod_wsgi • Apache/lighttpd + FastCGI • SCGI, AJP, nginx/mod_wsgi, ... 107
    352. Use mod_wsgi 108
    353. WSGIScriptAlias / /home/mysite/mysite.wsgi 109
    354. import os, sys # Add to PYTHONPATH whatever you need sys.path.append('/usr/local/django') # Set DJANGO_SETTINGS_MODULE os.environ['DJANGO_SETTINGS_MODULE'] = 'mysite.settings' # Create the application for mod_wsgi import django.core.handlers.wsgi application = django.core.handlers.wsgi.WSGIHandler() 110
    355. “Scale” 111
    356. Does this scale? django database media server 112
    357. Does this scale? django database media server Maybe! 112
    358. Things per secong Number of things 113
    359. Real-world example Database A 175 req/s Database B 75 req/s 114
    360. Real-world example http://tweakers.net/reviews/657/6 115
    361. django media web server database database server 116
    362. Why separate hardware? 117
    363. Why separate hardware? • Resource contention 117
    364. Why separate hardware? • Resource contention • Separate performance concerns 117
    365. Why separate hardware? • Resource contention • Separate performance concerns • 0 → 1 is much harder than 1 → N 117
    366. DATABASE_HOST = '10.0.0.100' 118
    367. DATABASE_HOST = '10.0.0.100' FAIL 118
    368. Connection middleware 119
    369. Connection middleware • Proxy between web and database layers 119
    370. Connection middleware • Proxy between web and database layers • Most implement hot fallover and connection pooling 119
    371. Connection middleware • Proxy between web and database layers • Most implement hot fallover and connection pooling • Some also provide replication, load balancing, parallel queries, connection limiting, &c 119
    372. Connection middleware • Proxy between web and database layers • Most implement hot fallover and connection pooling • Some also provide replication, load balancing, parallel queries, connection limiting, &c • DATABASE_HOST = '127.0.0.1' 119
    373. Connection middleware 120
    374. Connection middleware • PostgreSQL: pgpool 120
    375. Connection middleware • PostgreSQL: pgpool • MySQL: MySQL Proxy 120
    376. Connection middleware • PostgreSQL: pgpool • MySQL: MySQL Proxy • Database-agnostic: sqlrelay 120
    377. Connection middleware • PostgreSQL: pgpool • MySQL: MySQL Proxy • Database-agnostic: sqlrelay • Oracle: ? 120
    378. django media web server media server database database server 121
    379. Media server traits 122
    380. Media server traits • Fast 122
    381. Media server traits • Fast • Lightweight 122
    382. Media server traits • Fast • Lightweight • Optimized for high concurrency 122
    383. Media server traits • Fast • Lightweight • Optimized for high concurrency • Low memory overhead 122
    384. Media server traits • Fast • Lightweight • Optimized for high concurrency • Low memory overhead • Good HTTP citizen 122
    385. Media servers 123
    386. Media servers • Apache? 123
    387. Media servers • Apache? • lighttpd 123
    388. Media servers • Apache? • lighttpd • nginx 123
    389. Media servers • Apache? • lighttpd • nginx • S3 123
    390. The absolute minimum django media web server media server database database server 124
    391. The absolute minimum django media database web server 125
    392. proxy media load balancer media server django django django web server cluster database database server 126
    393. Why load balancers? 127
    394. Load balancer traits 128
    395. Load balancer traits • Low memory overhead 128
    396. Load balancer traits • Low memory overhead • High concurrency 128
    397. Load balancer traits • Low memory overhead • High concurrency • Hot fallover 128
    398. Load balancer traits • Low memory overhead • High concurrency • Hot fallover • Other nifty features... 128
    399. Load balancers 129
    400. Load balancers • Apache + mod_proxy 129
    401. Load balancers • Apache + mod_proxy • perlbal 129
    402. Load balancers • Apache + mod_proxy • perlbal • nginx 129
    403. Load balancers • Apache + mod_proxy • perlbal • nginx • Varnish 129
    404. Load balancers • Apache + mod_proxy • perlbal • nginx • Varnish • Squid 129
    405. CREATE POOL mypool POOL mypool ADD 10.0.0.100 POOL mypool ADD 10.0.0.101 CREATE SERVICE mysite SET listen = my.public.ip SET role = reverse_proxy SET pool = mypool SET verify_backend = on SET buffer_size = 120k ENABLE mysite 130
    406. you@yourserver:~$ telnet localhost 60000 pool mysite add 10.0.0.102 OK nodes 10.0.0.101 10.0.0.101 lastresponse 1237987449 10.0.0.101 requests 97554563 10.0.0.101 connects 129242435 10.0.0.101 lastconnect 1237987449 10.0.0.101 attempts 129244743 10.0.0.101 responsecodes 200 358 10.0.0.101 responsecodes 302 14 10.0.0.101 responsecodes 207 99 10.0.0.101 responsecodes 301 11 10.0.0.101 responsecodes 404 18 10.0.0.101 lastattempt 1237987449 131
    407. proxy proxy proxy media media load balancing cluster media server cluster django django django cache cache web server cluster cache cluster database database database database server cluster 132
    408. “Shared nothing” 133
    409. BALANCE = None def balance_sheet(request): global BALANCE if not BALANCE: bank = Bank.objects.get(...) BALANCE = bank.total_balance() ... 134
    410. BALANCE = None def balance_sheet(request): global BALANCE if not BALANCE: bank = Bank.objects.get(...) BALANCE = bank.total_balance() ... FAIL 134
    411. Global variables are right out 135
    412. from django.cache import cache def balance_sheet(request): balance = cache.get('bank_balance') if not balance: bank = Bank.objects.get(...) balance = bank.total_balance() cache.set('bank_balance', balance) ... 136
    413. from django.cache import cache def balance_sheet(request): balance = cache.get('bank_balance') if not balance: bank = Bank.objects.get(...) balance = bank.total_balance() cache.set('bank_balance', balance) ... WIN 136
    414. def generate_report(request): report = get_the_report() open('/tmp/report.txt', 'w').write(report) return redirect(view_report) def view_report(request): report = open('/tmp/report.txt').read() return HttpResponse(report) 137
    415. def generate_report(request): report = get_the_report() open('/tmp/report.txt', 'w').write(report) return redirect(view_report) def view_report(request): report = open('/tmp/report.txt').read() return HttpResponse(report) FAIL 137
    416. Filesystem? What filesystem? 138
    417. Further reading 139
    418. Further reading • Cal Henderson, Building Scalable Web Sites 139
    419. Further reading • Cal Henderson, Building Scalable Web Sites • John Allspaw, The Art of Capacity Planning 139
    420. Further reading • Cal Henderson, Building Scalable Web Sites • John Allspaw, The Art of Capacity Planning • http://kitchensoap.com/ 139
    421. Further reading • Cal Henderson, Building Scalable Web Sites • John Allspaw, The Art of Capacity Planning • http://kitchensoap.com/ • http://highscalability.com/ 139
    422. Monitoring 140
    423. Goals 141
    424. Goals • When the site goes down, know it immediately. 141
    425. Goals • When the site goes down, know it immediately. • Automatically handle common sources of downtime. 141
    426. Goals • When the site goes down, know it immediately. • Automatically handle common sources of downtime. • Ideally, handle downtime before it even happens. 141
    427. Goals • When the site goes down, know it immediately. • Automatically handle common sources of downtime. • Ideally, handle downtime before it even happens. • Monitor hardware usage to identify hotspots and plan for future growth. 141
    428. Goals • When the site goes down, know it immediately. • Automatically handle common sources of downtime. • Ideally, handle downtime before it even happens. • Monitor hardware usage to identify hotspots and plan for future growth. • Aid in postmortem analysis. 141
    429. Goals • When the site goes down, know it immediately. • Automatically handle common sources of downtime. • Ideally, handle downtime before it even happens. • Monitor hardware usage to identify hotspots and plan for future growth. • Aid in postmortem analysis. • Generate pretty graphs. 141
    430. Availability monitoring principles 142
    431. Availability monitoring principles • Check services for availability. 142
    432. Availability monitoring principles • Check services for availability. • More then just “ping yoursite.com.” 142
    433. Availability monitoring principles • Check services for availability. • More then just “ping yoursite.com.” • Have some understanding of dependancies. 142
    434. Availability monitoring principles • Check services for availability. • More then just “ping yoursite.com.” • Have some understanding of dependancies. • Notify the “right” people using the “right” methods, and don’t stop until it’s fixed. 142
    435. Availability monitoring principles • Check services for availability. • More then just “ping yoursite.com.” • Have some understanding of dependancies. • Notify the “right” people using the “right” methods, and don’t stop until it’s fixed. • Minimize false positives. 142
    436. Availability monitoring principles • Check services for availability. • More then just “ping yoursite.com.” • Have some understanding of dependancies. • Notify the “right” people using the “right” methods, and don’t stop until it’s fixed. • Minimize false positives. • Automatically take action against common sources of downtime. 142
    437. Availability monitoring tools 143
    438. Availability monitoring tools • Internal tools 143
    439. Availability monitoring tools • Internal tools • Nagios 143
    440. Availability monitoring tools • Internal tools • Nagios • Monit 143
    441. Availability monitoring tools • Internal tools • Nagios • Monit • Zenoss 143
    442. Availability monitoring tools • Internal tools • Nagios • Monit • Zenoss • ... 143
    443. Availability monitoring tools • Internal tools • Nagios • Monit • Zenoss • ... • External monitoring tools 143
    444. Usage monitoring 144
    445. Usage monitoring • Keep track of resource usage over time. 144
    446. Usage monitoring • Keep track of resource usage over time. • Spot and identify trends. 144
    447. Usage monitoring • Keep track of resource usage over time. • Spot and identify trends. • Aid in capacity planning and management. 144
    448. Usage monitoring • Keep track of resource usage over time. • Spot and identify trends. • Aid in capacity planning and management. • Look good in reports to your boss. 144
    449. Usage monitoring tools 145
    450. Usage monitoring tools • RRDTool 145
    451. Usage monitoring tools • RRDTool • Munin 145
    452. Usage monitoring tools • RRDTool • Munin • Cacti 145
    453. Usage monitoring tools • RRDTool • Munin • Cacti • Graphite 145
    454. 146
    455. 147
    456. Logging 148
    457. Logging • Record information about what’s happening right now. 148
    458. Logging • Record information about what’s happening right now. • Analyze historical data for trends. 148
    459. Logging • Record information about what’s happening right now. • Analyze historical data for trends. • Provide postmortem information after failures. 148
    460. Logging tools 149
    461. Logging tools • print 149
    462. Logging tools • print • Python’s logging module 149
    463. Logging tools • print • Python’s logging module • syslogd 149
    464. Log analysis 150
    465. Log analysis • grep | sort | uniq -c | sort -rn 150
    466. Log analysis • grep | sort | uniq -c | sort -rn • Load log data into relational databases, then slice & dice. 150
    467. Log analysis • grep | sort | uniq -c | sort -rn • Load log data into relational databases, then slice & dice. • OLAP/OLTP engines. 150
    468. Log analysis • grep | sort | uniq -c | sort -rn • Load log data into relational databases, then slice & dice. • OLAP/OLTP engines. • Splunk. 150
    469. Log analysis • grep | sort | uniq -c | sort -rn • Load log data into relational databases, then slice & dice. • OLAP/OLTP engines. • Splunk. • Analog, AWStats, ... 150
    470. Log analysis • grep | sort | uniq -c | sort -rn • Load log data into relational databases, then slice & dice. • OLAP/OLTP engines. • Splunk. • Analog, AWStats, ... • Google Analytics, Mint, ... 150
    471. What to monitor? 151
    472. What to monitor? • Everything possible. 151
    473. What to monitor? • Everything possible. • The answer to “should I monitor this?” is always “yes.” 151
    474. Performance And when you should care. 152
    475. Ignore performance 153
    476. Ignore performance Step 1: write your app. 153
    477. Ignore performance Step 1: write your app. Step 2: make it work. 153
    478. Ignore performance Step 1: write your app. Step 2: make it work. Step 3: get it live. 153
    479. Ignore performance Step 1: write your app. Step 2: make it work. Step 3: get it live. Step 4: get some users. 153
    480. Ignore performance Step 1: write your app. Step 2: make it work. Step 3: get it live. Step 4: get some users. … 153
    481. Ignore performance Step 1: write your app. Step 2: make it work. Step 3: get it live. Step 4: get some users. … Step 94,211: tune. 153
    482. Ignore performance 154
    483. Ignore performance • Code isn’t “fast” or “slow” until it’s deployed in production. 154
    484. Ignore performance • Code isn’t “fast” or “slow” until it’s deployed in production. • That said, often bad code is obvious. So don’t write it. 154
    485. Ignore performance • Code isn’t “fast” or “slow” until it’s deployed in production. • That said, often bad code is obvious. So don’t write it. • YAGNI doesn’t mean you get to be an idiot. 154
    486. Low-hanging fruit 155
    487. Low-hanging fruit • Lots of DB queries. 155
    488. Low-hanging fruit • Lots of DB queries. • Rule of thumb: O(1) queries per view. 155
    489. Low-hanging fruit • Lots of DB queries. • Rule of thumb: O(1) queries per view. • Very complex queries. 155
    490. Low-hanging fruit • Lots of DB queries. • Rule of thumb: O(1) queries per view. • Very complex queries. • Read-heavy vs. write-heavy. 155
    491. Anticipate bottlenecks 156
    492. Anticipate bottlenecks • It’s probably going to be your DB. 156
    493. Anticipate bottlenecks • It’s probably going to be your DB. • If not, it’ll be I/O. 156
    494. “It’s slow!” 157
    495. Define “slow” 158
    496. Define “slow” • Benchmark in the browser. 158
    497. Define “slow” • Benchmark in the browser. • Compare to wget/curl. 158
    498. Define “slow” • Benchmark in the browser. • Compare to wget/curl. • The results can be surprising. 158
    499. Define “slow” • Benchmark in the browser. • Compare to wget/curl. • The results can be surprising. • Often, “slow” is a matter of perceived performance. 158
    500. 159
    501. YSlow http://developer.yahoo.com/yslow/ 160
    502. Server-side performance tuning 161
    503. Tuning in a nutshell 162
    504. Tuning in a nutshell • Cache. 162
    505. Tuning in a nutshell • Cache. • Cache some more. 162
    506. Tuning in a nutshell • Cache. • Cache some more. • Improve your caching strategy. 162
    507. Tuning in a nutshell • Cache. • Cache some more. • Improve your caching strategy. • Add more cache layers. 162
    508. Tuning in a nutshell • Cache. • Cache some more. • Improve your caching strategy. • Add more cache layers. • Then, maybe, tune your code. 162
    509. Caching is magic 163
    510. Caching is magic • Turns less hardware into more! 163
    511. Caching is magic • Turns less hardware into more! • Makes slow code fast! 163
    512. Caching is magic • Turns less hardware into more! • Makes slow code fast! • Lowers hardware budgets! 163
    513. Caching is magic • Turns less hardware into more! • Makes slow code fast! • Lowers hardware budgets! • Delays the need for new servers! 163
    514. Caching is magic • Turns less hardware into more! • Makes slow code fast! • Lowers hardware budgets! • Delays the need for new servers! • Cures scurvy! 163
    515. Caching is about trade-offs 164
    516. Caching questions 165
    517. Caching questions • Cache for everybody? Only logged-in users? Only non-paying users? 165
    518. Caching questions • Cache for everybody? Only logged-in users? Only non-paying users? • Long timeouts/stale data? Short timeouts/ worse performance? 165
    519. Caching questions • Cache for everybody? Only logged-in users? Only non-paying users? • Long timeouts/stale data? Short timeouts/ worse performance? • Invalidation: time-based? Data based? Both? 165
    520. Caching questions • Cache for everybody? Only logged-in users? Only non-paying users? • Long timeouts/stale data? Short timeouts/ worse performance? • Invalidation: time-based? Data based? Both? • Just cache everything? Or just some views? Or just the expensive parts? 165
    521. Caching questions • Cache for everybody? Only logged-in users? Only non-paying users? • Long timeouts/stale data? Short timeouts/ worse performance? • Invalidation: time-based? Data based? Both? • Just cache everything? Or just some views? Or just the expensive parts? • Django’s cache layer? Proxy caches? 165
    522. Common caching strategies 166
    523. Common caching strategies • Are most of your users anonymous? Use CACHE_MIDDLEWARE_ANONYMOUS_ONLY 166
    524. Common caching strategies • Are most of your users anonymous? Use CACHE_MIDDLEWARE_ANONYMOUS_ONLY • Are there just a couple of slow views? Use @cache_page. 166
    525. Common caching strategies • Are most of your users anonymous? Use CACHE_MIDDLEWARE_ANONYMOUS_ONLY • Are there just a couple of slow views? Use @cache_page. • Need to cache everything? Use a site wide cache. 166
    526. Common caching strategies • Are most of your users anonymous? Use CACHE_MIDDLEWARE_ANONYMOUS_ONLY • Are there just a couple of slow views? Use @cache_page. • Need to cache everything? Use a site wide cache. • Everything except a few views? Use @never_cache. 166
    527. Site-wide caches 167
    528. Site-wide caches • Good: Django’s cache middleware. 167
    529. Site-wide caches • Good: Django’s cache middleware. • Better: A proper upstream cache. (Squid, Varnish, …). 167
    530. External caches 168
    531. External caches • Most work well with Django. 168
    532. External caches • Most work well with Django. • Internally, Django just uses HTTP headers to control caching; those headers are exposed to external caches. 168
    533. External caches • Most work well with Django. • Internally, Django just uses HTTP headers to control caching; those headers are exposed to external caches. • Cached requests never even hit Django. 168
    534. Conditional view processing 169
    535. 170
    536. GET / HTTP/1.1 Host: www2.ljworld.com/ 170
    537. GET / HTTP/1.1 Host: www2.ljworld.com/ HTTP/1.1 200 OK Server: Apache Expires: Wed, 17 Jun 2009 18:17:18 GMT ETag: "93431744c9097d4a3edd4580bf1204c4" … 170
    538. GET / HTTP/1.1 Host: www2.ljworld.com/ HTTP/1.1 200 OK Server: Apache Expires: Wed, 17 Jun 2009 18:17:18 GMT ETag: "93431744c9097d4a3edd4580bf1204c4" … GET / HTTP/1.1 Host: www2.ljworld.com/ If-None-Match: "93431744c9097d4a3edd4580bf1204c4" HTTP/1.1 304 NOT MODIFIED … 170
    539. GET / HTTP/1.1 Host: www2.ljworld.com/ HTTP/1.1 200 OK Server: Apache Expires: Wed, 17 Jun 2009 18:17:18 GMT ETag: "93431744c9097d4a3edd4580bf1204c4" … GET / HTTP/1.1 Host: www2.ljworld.com/ If-None-Match: "93431744c9097d4a3edd4580bf1204c4" HTTP/1.1 304 NOT MODIFIED … GET / HTTP/1.1 Host: www2.ljworld.com/ If-Modified-Since: Wed, 17 Jun 2009 18:00:00 GMT 170
    540. GET / HTTP/1.1 Host: www2.ljworld.com/ HTTP/1.1 200 OK Server: Apache Expires: Wed, 17 Jun 2009 18:17:18 GMT ETag: "93431744c9097d4a3edd4580bf1204c4" … GET / HTTP/1.1 Host: www2.ljworld.com/ If-None-Match: "93431744c9097d4a3edd4580bf1204c4" HTTP/1.1 304 NOT MODIFIED … GET / HTTP/1.1 Host: www2.ljworld.com/ If-Modified-Since: Wed, 17 Jun 2009 18:00:00 GMT HTTP/1.1 304 NOT MODIFIED … 170
    541. Etags 171
    542. Etags • Opaque identifiers for a resource. 171
    543. Etags • Opaque identifiers for a resource. • Cheaper to compute than the resource itself. 171
    544. Etags • Opaque identifiers for a resource. • Cheaper to compute than the resource itself. • Bad: “17”, “some title”, etc. 171
    545. Etags • Opaque identifiers for a resource. • Cheaper to compute than the resource itself. • Bad: “17”, “some title”, etc. • Good: “93431744c9097d4a3edd4580bf1204c4”, “74c05a20-5b6f-11de-adc7-001b63944e73”, etc. 171
    546. When caching fails… 172
    547. “I think I need a bigger box.” 173
    548. Where to spend money 174
    549. Where to spend money • First, buy more RAM. 174
    550. Where to spend money • First, buy more RAM. • Then throw money at your DB. 174
    551. Where to spend money • First, buy more RAM. • Then throw money at your DB. • Then buy more web servers. 174
    552. No money? 175
    553. Web server improvements 176
    554. Web server improvements • Start with simple improvements: turn off Keep-Alive, tweak MaxConnections; etc. 176
    555. Web server improvements • Start with simple improvements: turn off Keep-Alive, tweak MaxConnections; etc. • Use a better application server (mod_wsgi). 176
    556. Web server improvements • Start with simple improvements: turn off Keep-Alive, tweak MaxConnections; etc. • Use a better application server (mod_wsgi). • Investigate light-weight web servers (nginx, lighttpd). 176
    557. Database tuning 177
    558. Database tuning • Whole books can be — and many have been — written about DB tuning. 177
    559. Database tuning • Whole books can be — and many have been — written about DB tuning. • MySQL: High Performance MySQL http://www.amazon.com/dp/0596101716/ 177
    560. Database tuning • Whole books can be — and many have been — written about DB tuning. • MySQL: High Performance MySQL http://www.amazon.com/dp/0596101716/ • PostgreSQL: http://www.revsys.com/writings/postgresql-performance.html 177
    561. Build a toolkit 178
    562. Build a toolkit • profile, cProfile 178
    563. Build a toolkit • profile, cProfile • strace, SystemTap, dtrace. 178
    564. Build a toolkit • profile, cProfile • strace, SystemTap, dtrace. • Django debug toolbar                                http://bit.ly/django-debug-toolbar 178
    565. More… http://jacobian.org/r/django-cache http://jacobian.org/r/django-conditional-views 179
    566. Final thoughts 180
    567. Final thoughts • Writing the code is the easy part. 180
    568. Final thoughts • Writing the code is the easy part. • Making it work in the Real World is that part that’ll make you lose sleep. 180
    569. Final thoughts • Writing the code is the easy part. • Making it work in the Real World is that part that’ll make you lose sleep. • Don’t worry too much: performance problems are good problems to have. 180
    570. Final thoughts • Writing the code is the easy part. • Making it work in the Real World is that part that’ll make you lose sleep. • Don’t worry too much: performance problems are good problems to have. • But worry a little bit: “an ounce of prevention is worth a pound of cure.” 180
    571. Fin. Contact me: jacob@jacobian.org / @jacobian Hire me: http://revsys.com/ 181

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