at Jonathan Marmor Software Developer, exfm email@example.comTuesday, October 2, 12Hi, I’m Jonathan Marmor, a software developer at exfm.Today I’m going to talk about* what exfm does,* how exfm uses MongoDB,* and tell you a little about the Monthly Music Hackathon I’m organizing.First I should tell you a little about me, to lower your expectations a bit. :)* musician, all of my schooling is in music* use python as tool to help compose music* not an expert in mongo* not going to talk about advanced topics* instead will talk basic practicalities of how mongo is used at exfm* if you want more details, get in touch and I’ll pass you off to our CTO, Lucas
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12what exfm does: going to get into this in some depthhow exfm uses mongo:environment which software we usemodels how our data is organized, how our code is organizedserver architecture brief overview of our hardwaremanagement and tools monitoring, scripting, handy stufffuture plans how we’re going to blow it up and put it back together againmonthly music hackathon nyc: fun part
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12
Browser extension Turns websites into playlistsTuesday, October 2, 12We have a browser extension It turns websites into playlistsIt makes it easier to listen to music which has been posted on a website For example: (next)
Soundcloud Music player!Tuesday, October 2, 12For example, if I visit this Soundcloud page with the extension installed it pops up on the bottomWow, a music player!I can click play and start listening to the songs on this page
Expanded Soundcloud music player!Tuesday, October 2, 12If I expand it * I can see the Playlist that was discovered on this website, * Re-order the songs, * Subscribe to be notiﬁed of new music posted to this website, * Love a song, * Share a song, * etc
Expanded Bandcamp music player!Tuesday, October 2, 12Also works on Bandcamp,
Expanded archive.org music player!Tuesday, October 2, 12and archive.org, and basically any other website with audio URLs or an open API to retrieve audio(that we’ve implemented, of course)
Music I’ve posted Full-width on my Tumblr blog music player!Tuesday, October 2, 12And also Tumblrbut this actually isn’t a browser extension, it’s a plugin you can install on any website.So visitors to the website get the exfm extension experience without having the extension installedThere’s a choice between the little guy in the bottom right and this full-width player.But let’s say you press play, and hear the strange sounds I’ve blogged about and think “What the heck is a Subharmonic Ogdoad with 12 Tones?”So you go to wikipedia...
Navigate away and keep listening!Tuesday, October 2, 12Oops! The music stopped because I’m not on the music site anymore!But not with the exfm extension. The music keeps playing.Possibly the most can’t-live-without feature of the extensionis that you can navigate away from the page where you found the music you are listening toand continue listening.So the extension is handy and fun, but...Only nerds use extensions Only a small percentage of our users have the extension installed The majority of our users use our Apps.
Push play, listen to music WebappTuesday, October 2, 12Where you can Push play and listen to music right awaywe have a website: http://ex.fm* Search tens of millions of tracks* Subscribe to your friends’ loved songs* Share to FB, twitter, tumblr* Scrobble to lastfm* Explore the collection in a variety of ways
Push play, listen to music iOSTuesday, October 2, 12also have iOS with a similar set of features...and (next)
Push play, listen to music AndroidTuesday, October 2, 12Android.But where does the content come from? It is all from Extensions and websites users are subscribed to (which we scrape for new audio).So we’re not indiscriminately scraping the web for audio: We have an army of critics and connoisseurs getting to the most important music ﬁrst,and we have their listening, loving, and sharing data to help us bubble up the best music.
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12So that gives of quite a bit of data to take care of.So now, we’ll shift gears and talk about how we deal with the data.
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12What are the core technologies we use?
Environment overview • Amazon Web Services for all infrastructure • Ubuntu • Python • Flask web framework • Rabbit/Celery for background tasks • Supervisord for process control • Fabric for deployment and scripting • MongoDBTuesday, October 2, 12(read the slide)and of course, MongoDB.If you want to talk to me about any of the non-mongo items on this list please get in touch.
Environment overview • MongoEngine http://mongoengine.org/ "MongoEngine is a Document-Object Mapper (think ORM, but for document databases) for working with MongoDB from Python. It uses a simple declarative API, similar to the Django ORM."Tuesday, October 2, 12MongoEngine is a core part of how exfm uses Mongo.Most of our application’s shape and logic are hung from subclasses of MongoEngine’s classes.If you don’t know MongoEngine I highly encourage you to read the source code. It’s good stuff.It makes it easy to describe your data and deﬁne methods for creating, getting, and modifying it.
Environment overview • AWS CloudSearch http://aws.amazon.com/cloudsearch/ "Amazon CloudSearch is a fully- managed search service in the cloud”Tuesday, October 2, 12Amazon CloudSearch is also a core part of how we use Mongo.It mercifully replaced Solr for us.Allowed us to remove indexes of non-primary key ﬁelds. Many complex queries are done via CloudSearch.We dump data from Mongo, upload to S3, CloudSearch indexes.Queries to CloudSearch spit out primary keys of our Mongo collections so retrieval from Mongo is trivial. (from a query perspective)
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12So that’s our environment.Now to our models.
Models Collections • Songs • Users • Sites • Many embedded documents • Several collections thatUsers, Songs, and relationships between express SitesTuesday, October 2, 12We have three primary collections (that I’ll be talking about today) 1. Songs 2. Users 3. SitesThen we also have numerous embedded documents that are literally a part of the documents of the three primary collections.And several collections that express relationships between songs users and sites
Models File organization • Module for user.py, song.py,related collections: each group of site.py • Base engine.py ﬁle MongoEngine middleware building on top of with customTuesday, October 2, 12We like to keep things simple: we have one ﬁle for each collection: song.py user.py site.pyThen an engine.py ﬁle where we extend some MongoEngine classes and have some custom middleware. (next)
Models Custom middleware • _ExfmDocument: convenience methods for initializing, saving, reloading, and updating documents and querying collections • _ExfmQuerySet: convenience methods for handling query results, such as paging and updating the returned documents • cached_property: decorator to cache a value in the local object rather than grabbing from the DB • Logging setupTuesday, October 2, 12_ExfmDocument: Base Class for all our document classes such as Song, User, and Sitehas convenience methods for initializing, saving, reloading, and updating documents and querying collections_ExfmQuerySet: inherits mongoengine.queryset.QuerySet. Is what all our queries return.has convenience methods for handling query results, such as paging and updating the returned documentsWe also have other nice little things in engine.py, like logging setup, document method wrappers, etc.
Models Primary Keys • Songs: sequential integers • Users: username string • Sites: MD5 hash of URL • Try to avoid too much variation in primary key size • Frequently use compound keys, eg: jonathan_facebook, and deal with parsing the string rather than using a complex queryTuesday, October 2, 12Now a bit about our schema design.Choosing what your primary keys are is really important. Through trial and error, we’ve settled on IDs that don’t screw up performance and allow us to simplify queries.We try to avoid extreme variation in ID length within a collection.For example, if a URL is your ID, make a hash that has a ﬁxed width.http://ex.fm is not the same size as some super long URL.Also, we use “compound keys” that have meaningful data in them. This allows us to skip some queries entirely:For example: I have a UserService object’s key: “jonathan_facebook.” I don’t need the UserService object, I just need the User with username “jonathan”So I just parse out the username from the UserService key and query the User collection with the username jonathan and skip querying the UserService collection.There are several other ways compound keys are helpful as well.
Models Indexes • Songs: sequential id, MD5 hash of URL • Users: username, email, MD5 hash of username • Sites: MD5 hash of URL • Always retrieve by MD5 hashTuesday, October 2, 12Choosing which ﬁelds are indexed is also critical.We used to have 5 to 10 indexes per collection. This created huge bloat in our memory usage.So we try to get away with only accessing objects by primary key.
Models Common properties • strings, ints, booleans, dates... normal stuff • lists of strings, lists of embedded docsTuesday, October 2, 12Remember when I said MongoEngine uses a declarative syntax for describing your data?This is how it looks. You list your ﬁeld names, and their data types and MongoEngine handles the marshalling and casting and dirty stuff.You’ll see there are a variety of types of ﬁelds: strings, ints, dates, lists of strings, embedded documents, dictionaries, lists of embedded documents...See that “image” ﬁeld? EmbeddedDocumentField(SongImage)? (next)
Models Example of embedded documentTuesday, October 2, 12That’s just some extra ﬁelds. From my perspective as a user, the main ramiﬁcation of this pattern is that you can access the properties with dot notation, like: user.image.smallAlso embedded docs can be repeated in lists.
Models Example of collection that expresses a relationshipTuesday, October 2, 12Here’s an example of a collection that has documents that express relationships betweendocs in other collections.The basic gist is that the song is added to a list of songs this user has loved.But this isn’t done on a User object, it’s done in the _UserLoved collection, which has an object for each user, which is just a list of that user’s loved songs (plus some metadata and housekeeping stuff).And the list of songs this user has loved, are embedded documents: the _UserLovedSong object which contains the data pertinent to the event of this user loving this song.Then (not shown here) the mirror image of this process happens on the Song that is being loved: in other words, the user is added to a list of users who have loved the song.
Models Class methods • create, get_or_create, getters, settersTuesday, October 2, 12Moving on, this these are examples of some typical methods that operate on the collection as opposed to operating on a document.The ﬁrst is the create method of the Song object. It actually instantiates a new Song instance, saves it to the remote DB, and returns it. Simple, but it’s a very nice shortcut: song.create(‘song_url’)The seconds is Song.get_by_id. If this gets a list of IDs, it uses one of our custom helpers to get multiple songs from the DB and return them in the order we asked for them. If it gets a single ID, it just retrieves that song.
Models Instance methodsTuesday, October 2, 12And this is an example of a method that operates on a speciﬁc document from the song collection.Calling .love on a Song instance and giving it a username, creates a new SongLovedUser which contains the user ID (and other data arising from the loving event)then adds that object to a list of users who have loved this song
Models More advanced topics • Querying • BucketingTuesday, October 2, 12I’m not going to get into these here.Our solution for dealing with complex queries: use CloudSearch.Bucketing is our current solution for dealing with objects in the same collection that have very different size.Send me an email if you want to know more.
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12So now brieﬂy I’ll go over our server setup.We use AWS for everything except our laptops, mobile phones, tablets, Raspberry Pis, and we’ve been talking about building a CNC lathe.
Server architecture • One Primary: m2.4xlarge • One Secondary: m2.4xlarge • One Arbiter: t1.micro • One shared all-in-one m1.large for stagingTuesday, October 2, 12We don’t do sharding clustering... we’re still on one gigantic machine.Our primary is the recently released m2.4xlarge, which is a giant honking beast.So is our secondary, which we fail over to should something happen to the primary. This has happened. Failover appears to work. :)There is also a tiny “arbiter” machine.Then we also have one machine for staging which we dump to periodically so it somewhat resembles production.
m2.4xlarge: “High-Memory Quadruple Extra Large Instance” 68.4 GB of memory 64-bit RAID0 EBS volume Recent UbuntuTuesday, October 2, 12When these behemoth m2.4xlarges were recently released we immediately upgraded from m2.2xlarges.All that extra memory has deﬁnitely made our lives easier. Fewer alerts in the middle of the night.We have a somewhat elaborate Elastic Block Storage RAID0 conﬁguration which I didn’t set up.Send me an email if you want to learn more about that.
1. What does exfm do? 2. Who are you? 3. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 4. Monthly Music Hackathon NYCTuesday, October 2, 12Here are a few of the tools we use to keep our sanity.
Management and tools Backup • Use AWS EC2 tools in boto to snapshot EBS volumes from secondary once per hour • 10gen’s backup-agent • also sync to beta for staging (ok, that’s not backup, but it’s a script that works similarly)Tuesday, October 2, 12Snapshots via AWS using Boto, which an amazing and comprehensive python client for all things AWS, in case you don’t know about it.
Management and tools Monitoring • MMS • AWS CloudWatchTuesday, October 2, 12MMS is 10gen’s monitoring system for Mongo, which uses munin. It’s really terriﬁc and critical.AWS CloudWatch is Amazon’s monitoring system for all of their services. Is also terriﬁc and critical for monitoring servers and network stuff.CloudWatch has improved in the past year or so, and has made the great third party monitoring service, ServerDensity, unnecessary for us.
Management and tools Handy tools • mongo shell: interactive JS shell. Get collection stats, test queries, etc. • mongotop: per-collection read write times • iostat -x 2: Monitoring system I/O • tail -f logs/mongo.out.logTuesday, October 2, 12mongo shell: interactive JS shell. Get collection stats, test queries, etc.mongotop: per-collection read write timesiostat -x 2: Monitoring system I/Otail -f logs/mongo.out.log: maybe the most important one. Only slow queries show up here. It’s a great way to ﬁnd queries that are slowing you down, so you can ﬁx them.We use all of these (and others) multiple times a day.
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12Fortunately, we’re growing really fast. So we’re making some big changes to accommodate more users, more content, and more data.
Future plans • Split models into separate services “Build fast, scale when necessary... ...and it’s currently necessary.”Tuesday, October 2, 12We currently run one monolithic application with tightly coupled parts.We’re in the process of splitting it into isolated HTTP services: User, Song, Site, Metadata processing, AlbumArt, LoveMachine, etcOur biggest headache has been that a few thousand Songs have thousands of loves, but tens of millions have zero or one love.The LoveMachine is a separate service designed to manage relationships between users and songs and will ﬁx this problem.
1. What does exfm do? 2. How does exfm use MongoDB? 1. Environment overview 2. Models 3. Server architecture 4. Management and tools 5. Future plans 3. Monthly Music Hackathon NYCTuesday, October 2, 12And now for the funner part.
Saturday, October 20th 10 AM hacking starts / 8 PM concert of hacks in Soho @musichackathon monthlymusichackathon.orgTuesday, October 2, 12If you are a musician or have an interest in music, please come.FREE!The idea is to hack on music, and for the attendees (you) to decide what that means.It could mean working with music streaming company’s APIs, soldering together a new musical instrument, analyzing a library of music with DSP software, or rapidly writing and performing a new piece of music.It ends with a concert of the hacks created that day.Ensemble in residence this month: amazing virtuosic classical guitar/ﬂute duo, that plays some insane music.Sponsored in part by 10gen and exfm.
Thank you! at Jonathan Marmor Software Developer, exfm firstname.lastname@example.orgTuesday, October 2, 12Thanks so much for listening to me.Please get in touch if you want to know more about exfm or the hackathon.