Cross-platform logging and analytics

Logging & Analytics
For fun and proﬁt

Let me tell you about a bug

• ~2% of our customers were affected


• Resolved (WORKSFORME)


• People will complain, but they won’t send
me crash reports


• People will complain, but they won’t send
me crash reports
• Apple’s crash reporter shows no crashes

The conﬁdence you get from ﬁnding out about every crash,
anywhere in the world, is crucial to delivering a high quality
product that needs to be used in the wild. For those of us in
the consumer software business it's absolutely critical.You
can't rely on your customers to tell you about crashes—many
of them may not be technical enough, and most of them won't
bother to take time off of their own important work to give
you a useful crash report unless you make it completely
automatic. - Joel Spolsky

It’s 2012, don’t roll your own
Use quincykit.net

And everybody lived
happily ever after...

NSError *err = nil;
[somethingWithErr:&err];
if (err) {
UIAlertView *errorAlertView =
[[UIAlertView alloc]
initWithTitle:@”Error” message:[err
description] delegate:nil
cancelButtonTitle:OK
otherButtonTitles:nil];
[errorAlertView show];
[errorAlertView release];
}

I started maintaining
non-iOS code

http://github.com/drewcrawford/buildbot

How do I make money?

1. Customer hears about me
2. ????
3. Proﬁt!

How do I make money?

1. Customer hears about me
2. ???? What’s going on here?
3. Proﬁt!

Web Analytics
• How many different times does a person
visit my site before they convert?

Web Analytics
• How do my blog readers’ habits change
over time?

Web Analytics
over time?
• What indicators (referrers, time-on-site,
months of loyalty) correlate to high quality
users?

Web Analytics
over time?
• What indicators (referrers, time-on-site,
months of loyalty) correlate to high quality
users?
• Can I prioritize sales leads automatically by
their behavior on my site?

App Analytics
• Do websites, SEM ads, or product videos
matter?

App Analytics
matter?
• What causes people to make an IAP?

App Analytics
matter?
• Should the button be here or there?

App Analytics
matter?
• Is anyone really going to use this feature?

App Analytics
matter?
• Is anyone really going to use this feature?
• How many of my app users still use after 3
days?

Nothing on this page
answers any questions

Anatomy of a useful page
HOW???

[FlurryAnalytics
startSession:@"1R1NQX1SPPWD7SDPI9WZ"];
for(int i = 0; i < 5; i++) {
[FlurryAnalytics logEvent:@"In for loop"
withParameters:[NSDictionary dictionaryWithObject:
[NSNumber numberWithInt:i] forKey:@"i"]];
}

And then I waited
several hours...

And all I got was
this lousy summary

The world’s most
worthless pie chart

In fairness, you can
export a few hundred records into Excel

But if you want full logs
You’d better ask nicely

If only we had a machine
that could process large quantities of data...

These are views
Not models. They draw pretty pictures. They’re not
your data.

It walks like raw data export
It talks like raw data export
But it’s not.

Look for yourself: http://mixpanel.com/docs/api-
documentation/data-export-api#libs-python

We don't provide raw log exports at this
time. It is something we are considering
adding to our pipeline, so thanks for writing
in with the feature request. - Mixpanel

I’m not saying there’s a conspiracy to
keep you from getting real event logs
But don’t believe you can export your data until you
actually download & check the damn logs

The epic unit test
• I’m working on a complicated “big-data” project

• The unit tests parse 100ks of points and take
hours

• When your compile-build-run-test loop is
measured in hours, you debug from an execution
trace, not by stepping through code

• One day the 200MB+ execution traces wouldn’t
upload to our bug tracker any more

The epic unit test

• I was building custom tools to parse through the
huge log ﬁles and give me the info I needed to
debug after-the-fact
• There’s a complicated system of macros
controlling log levels of different components

The epic unit test

• Even with all these tools, rarely would I log the
right things.
• Logging the wrong things costs me hours to re-
run the test.
• Over and over again.

Bion has a similar problem

on a different project

I read this article

http://journal.paul.querna.org/articles/2011/12/26/log-for-
machines-in-json/

What if instead of this

[Mon Dec 26 09:14:46 2011] [info] [client 50.57.61.4] File does
not exist: /var/www/no-such-file

We log this
{
"timestamp": 1324830675.076,
"status": "404",
"short_message": "File does not exist: /var/www/no-such-file",
"host": "ord1.product.api0",
"facility": "httpd",
"errno": "ENOENT",
"remote_host": "50.57.61.4",
"remote_port": "40100",
"path": "/var/www/no-such-file",
"uri": "/no-such-file",
"level": 4,
"headers": {
"user-agent": "BadAgent/1.0",
"connection": "close",
"accept": "*/*"
},
"method": "GET",
"unique_id": ".rh-g2Tm.h-ord1.product.api0.r-axAIO3bO.c-9210.ts-1324830675.v-24e946e"
}

And instead of logging
to this

Then I can query

• By any element in the JSON dictionary
• Across multiple tiers (client, server, web)
• Across platforms
• I can assign a unique ID to an iOS event
and follow the API request across my whole
stack

If it serves up all FB’s content
Pretty sure it can handle a few million print statements

Have you ﬁgured out
the common problem?
we’re talking about

EVENTS

• printf / NSLog • e-mail received

• server logs • sales inquiry

• webapp logs • bug resolved

• page view • User taps button

• error • unit test run

• download notiﬁcation • patch committed

Why do we need 10 systems
to solve one problem?

Only four kinds of events

• Things logged only to stderr / console
• Things logged to a unified network log file
• Things somebody is notified about
• Things somebody gets woken up about

I’ve been playing with loggly

• So far, so good
• I downloaded the damn logs
• Events queryable in ~5s for me
• High-perf log import (raw sock available)
• Filter and query on a hadoop cluster console, a
few gotchas but pretty neat
• I’m routlinely pushing up 100k events per day
and I’m a tiny user

Searching by bug #
across platforms

Do you really expect
me to build that dict?
I just want to type NSLog(@”Something”);

The hardest part of this whole mess
is ﬁguring out what to log
and actually logging it

Remember this?

An event that happened three months ago can be the
most important thing to understand the events of today.

We can add state to
our log statement

• dict.username = “Frank”
• log(“something”) //username=Frank
• log(“something”) //username=Frank

To reduce the work

But we have to
remember to undo it
• dict.username = “bill”
• begin_session(bill)
• log(“something”)
• begin_session(james)
• log(“something else”) //oops!

Kind of like memory
management

• Balance malloc with free
• Balance retain with release
• Balance new with delete

But some memory is
auto-managed
int i = 0;
{
int j = 0;
//can access j and i
}
//can access only i

Can we use a similar trick
to build our logging dictionary?

JUCHE
• printf / NSLog
• e-mail received

• server logs
• sales inquiry

• webapp logs
• bug resolved

• page view
• User taps button

• error
• unit test run

• download
• patch committed
notiﬁcation

One library to rule them all

• iOS, Python
• Builds the dict with ease

• iOS, Python
• Builds the dict with ease
• Logs to stderr, loggly

Events are nested
• Today

Events are nested
• Today
• Got up

Events are nested
• Today
• Got up
• Made coffee

Events are nested
• Today
• Got up
• Made coffee
• Closed bugs

Events are nested
• Today
• Got up
• Made coffee
• Closed bugs
• Bug 1

Events are nested
• Today
• Got up
• Made coffee
• Closed bugs
• Bug 1
• Bug 2

Events are nested
• Today
• Got up
• Made coffee
• Closed bugs
• Bug 1
• Bug 2
• Had lunch

Events are scoped
• Today
• Got up
• Made coffee
• Closed bugs
• Bug 1
• Bug 2
• Had lunch
Inner items inherit the settings of outer items

for(int i = 0; i < 3; i++) {
[JucheLog revolt:@"i",[NSString
stringWithFormat:@"%d",i],^{
JUCHE(JINFO,@"My awesome
loop");
}];
}

for(int i = 0; i < 3; i++) {

[JucheLog revolt:@"i",[NSString stringWithFormat:@"%d",i],^{

JUCHE(JINFO,@"My awesome loop");

}];

}

| [INFO] 19:12:11 My awesome loop i=0 juchelog.py:142



for i in range(0,3):

with juche.revolution(i=i,eternal_president="kim-il-sun"):

juche.info("Outer loop!")

for j in range(0,2):

with juche.revolution(j=j):

juche.info("Inner loop!")

| [INFO] 19:12:11 Outer loop! i=0 eternal_president=kim-il-sun juchelog.py:147

| | [INFO] 19:12:11 Inner loop! j=0 juchelog.py:150

















{"function": "__block_global_0", "who": "G88014V4XYK", "indent": "2",
"thread": "main", "eternal_president": "kim-il-sun", "i": "2", "app":
"com.dca.JucheLogTestMac", "j": "2", "version": "1", "file":
"JucheLogTests.m", "msg": "Inner loop!", "line": "44", "level":
"info"}

Call for contributors

http://github.com/drewcrawford/JucheLog

Use the library


Use the library
See if it solves your problems


Use the library
Critique the syntax


Use the library
Critique the syntax
Critique the terminal output


Use the library
Critique the syntax
Port it to (PHP, RoR, JS...)


Use the library
Critique the syntax
Write convenience functions


Use the library
Critique the syntax
“Log every Y times”


Use the library
Critique the syntax
Log+UIAlertView


Use the library
Critique the syntax
Log+UIAlertView
Log more types (NSError)


Use the library
Critique the syntax
Log+UIAlertView
Log more types (NSError)
streamlined opt-out


I am not a lawyer
And this is not legal advice

17.1 Apps cannot transmit data about a user without
obtaining the user's prior permission and providing the
user with access to information about how and where
the data will be used

Your EULA says
Consent to Use of Data:You agree that Application
Provider may collect and use technical data and related
information, including but not limited to technical
information about Your device, system and application
software, and peripherals, that is gathered periodically
to facilitate the provision of software updates, product
support and other services to You (if any) related to the
Licensed Application. Application Provider may use this
information, as long as it is in a form that does not
personally identify You, to improve its products or to
provide services or technologies to You.

I use data
• To diagnose and ﬁx bugs and crashes

I use data
• To learn where users are getting stuck

I use data
• To learn what percentage of my customer
base experiences issues

I use data
• To plan new features and updates

I use data
• To A/B test and see what people like

I use data
• To understand my customers’ needs

I use data
• To understand my customers’ needs
• Always for the beneﬁt of the users

(Don’t even log personal data)

Try out Juche

Look for common problems
and build common solutions

• Tiny iOS Developer

• Mix of contracts &
products

• Many other dev tools
like JucheLog

Drew Crawford
http://drewcrawfordapps.com
drew@drewcrawfordapps.com

http://sealedabstract.com <--you should be reading this

Cross-platform logging and analytics

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