MongoDB Sharding

1. Eugene KovshilovskyTechnical Director, OperationsRick ChenTechnical DirectorCie Games, Inc.

2. Rick Chen Rick Chen is a Technical Director at CieGames, overseeing the company‟sengineering department. In 2012, Cie Games,the leading developer and publisher of socialand mobile games, was recognized as one ofthe Fastest Growing Company in NorthAmerica on Deloitte‟s Technology Fast 500 list.

3. Eugene Kovshilovsky Eugene Kovshilovsky is a Technical Director atCie Games, a leading developer and publisherof social and mobile games. Its popular game,Car Town, is the first Facebook game builtaround brands and has attracted more than 50million players worldwide. The company‟s firstiOS game, Car Town Streets, for iPhone, iPadand iPod touch, is one of the Top 10 Gameson the App Store in multiple countries.

4. What is Sharding? (Horizontal) partitioning in a database where data is split byrows (collections) instead or columns

5. Why Shard in Games? Write Throughput Exceeds I/O Each click updates the user‟s currency amount.

6. Why Shard in Games? Memory isn‟t large enough to hold active dataset

7. Why Shard in Games? You want to run on commodity hardware and scalehorizontally vs. vertically

8. MongoDB Sharding Distribute objects within collections automatically Choose how data is partitioned Single master to sharded cluster with = 0 down time Fully consistent Works well in the cloud Automated fail-over Java support with Spring integration for easy JSON to Objectmapping

9. Shard DesignShare the load amongst all shardsequallyHigh RandomnessHave the smallest working set possibleRoll with timeRecreate shard key from ObjectIdBe careful how you shard, no way back

10. 99.999% Most of our queries we have the ObjectId Client saves ObjectId for re-login at a later time I‟m this user and I want to do xyz with my car. No range based queries We don‟t do „find‟ this user in some range and query against ourmaster db, we can do this on our secondary data stores that arenot sharded or additional reporting systems.

11. Shard Behavior Attempt to insert data into pre-split chunks Increase cluster throughput by reducing overhead User Life Time of 3 Days Most new players expected to play for an average of 3 days Unbalanced chunks will be rebalanced during off-peak hours Rarely happens

12. Pre Split Creates chunks and moves them to different shards ahead oftime Creates 0 byte chunks equally to all shards One chunk may grow to 5-6 chunks depending on how manynew users come in within a 3 day window Used instead of waiting for the balancer to detect that thereare too many chunks in one shard

13. 3 Day Shard Key2^18 = 262144 seconds = 3.03 daysObjectId consists of the timestamp of when the_id is created“Consistent random” valueGenerate Md5 from String version of ObjectIdTake first 18 bit from Md5Append the 18 bit random value to thetimestamp

14. Mongo 2.4 and New HashSharding No need for Pre-splitting Easy setup of randomized shard key Better distribution of chunks on shards for isolated documentwrites and reads Uses first 64bit of md5 of the field Doesn‟t support compound indexes Don‟t use floating point numbers Range bases queries go to all shards Working set is distributed to all shards

15. Development EnvironmentSharded Cluster

16. Deploy Start the Config Server (mongod) Instances Start the mongos Instances Add Shards to the Cluster Enable Sharding for a Database Enable Sharding for a Collection

17. Start the Config Server DatabaseInstances Create data dir for each of the 3 config server instances Start the 3 config server instances If starting on the same machine for study purposes thenconfigure each one to run on a different portmkdir /data/configdbmongod –configsvr –dbpath /data/configdb –port 27019

18. Start the mongos Instances Ideally these lightweight instances run on the applicationserver(s) Start the mongos instances mongos –configdb <config server hostnames> If connecting to the demo configs on localhost then specify the config servers with the different ports. mongos run on port 27017 by defaultmongos –configdb cfg0.example.net:27019,cfg1.example.net:27019mongos –configdb localhost:27019,localhost:27020

19. Add Shards to the Cluster Connect to mongos from mongo shell Add each shard to the cluster using sh.addShard() In production always specify the replica setsh.addShard(“rs1/localhost:27017”)Mongo –host localhost –port 27017

20. Enable Sharding for a Database To shard collections you need to enable this first Add sharding to database usingsh.enableSharding((“<database>”)sh.enableSharding(“mydb”)

21. Enable Sharding for a Collection Enable sharing usingsh.shardCollection("<database>.<collection>", shard-key-pattern)sh.shardCollection(”mydb.shardcollection", {userId:1})

22. Demo Please check out our demo

23. Resources http://docs.mongodb.org/manual/sharding/ https://github.com/ekovshilovsky/mongo_java http://docs.mongodb.org/manual/administration/sharded-clusters/ http://docs.mongodb.org/manual/tutorial/deploy-shard-cluster/

24. We are hiring! http://www.ciegames.com/careers