Mongo admin'ing

Mongo Admin’ing Jesse Wolgamotttwitter: @jwo slides: http://github.com/jwo

Quick Install• Dev: brew install mongodb• Server: apt-get install mongodb • http://www.mongodb.org/display/ DOCS/Ubuntu+and+Debian+packages

Don’t Fear theCommand Line Mongoid / Mongo Mapper Ruby DriverCommand Line Javascript (mongo)

Quick Server Statusdbdb.system.namespaces.find()db.serverStatus()db.currentOp()

Command Line Basicsuse dbadb.collection.find({json params})db.collection.findOne({json params})db.collection.mapReduce(map,reduce)db.collection.save({json})

Why Bother?• Mongo queries enhance Mongoid queries• Drop to command line when needed• Game.where(:outcome=>{‘$in’=>[‘winning’ ,‘tie’]})• Game.collection.update({:outcome=>‘win ning’, ‘$set’=>{:winning=>true}})

All Admin is Command Line• Setup Replica Sets• Check on Status

Replica / Slave / Journaling“If you aren’t running a replica set, you don’t care about your data” -- Mongo DB dude

Master / Slave What You’d Expect M Slave Slave Slave

Master / Slave What You’d Expect M Writes Go Here Slave Slave Slave

Master / Slave What You’d Expect M Writes Go Here Slave Slave Slave Reads CAN Go Here

Replica Sets The new Hotness (and Recommended)Primary Secondary Secondary Secondary Arbiter

Replica Sets The new Hotness (and Recommended) Primary Secondary Secondary SecondaryWrites Go Here Arbiter

Replica Sets The new Hotness (and Recommended) Primary Secondary Secondary SecondaryWrites Go Here CAN Read Arbiter

Replica Sets The new Hotness (and Recommended) Primary Secondary Secondary SecondaryWrites Go Here CAN Read Arbiter Nothing Goes Here

Arbiter?• Arbiters exist when even number of hosts• They cast votes on primary elections• Can exist on your app server

Journaling• Added in 1.8• mongod -- journal• Will write out changes to a journal directory• You can restore from journal

Replica Set Funconfig = { _id: houstonrb, members: [ {_id: 0, host: localhost:20000}, {_id: 1, host: localhost:20001}, {_id: 2, host: localhost:20002, arbiterOnly: true}]}// Start it uprs.initiate(config);// Check it Outrs.status()// Who’s your daddy?rs.isMaster()

Non-Master Readserror: { "$err" : "not master", "code" : 10107 } OK, so we’ll do: db.getMongo().setSlaveOk() // Awesome

Backup / Restoremongodump --db houstonrbmongorestore --db houstonrb -ccollections --drop --indexesLastDirectoryName* Have all your .bson files in adirectory named your database

Repairing• The Data Gobbler -- mongodb likes hard- drive space and won’t give it back• Use mongod --repair to reclaim your space!

Nightly Planservice mongodb stop && mongod --repair --dbpath /var/lib/mongodb && service mongodb startrm -f /data/mongodump-backup.tar.bz2 && mongodump -o /data/backups && tar -jcf /data/mongodump-backup.tar.bz2 /data/backups && rm -rf /data/backups/

Catch Up!• When a Replica Set gets ‘stale’• rs.status will remain “5” (Recovering)• On Master, will say “Error RS102 too stale to catch up”• stop mongo on all servers, copy over all data ﬁles, including local.*, start all

Table Scans == Devil• When you get to 500,000 records, your DB may slow to crawl.• /var/log/mongodb/mongodb.log for logged queries (table scans)• db.collection.getIndexKeys()• Mongoid: rake db:mongoid:create_indexes

No, Really• I’ve been surprised LOTS at how often a table scan happens.• Test it out: mongod --notablescan• Stuﬀ will break.

Sharding• Don’t Shard Early• Helps in map-reduce• You deﬁne a “shard-key”, like lastname from A-H on this shard

Scaling (Secret Sauce)• Many Shard Masters, even more slaves• Add Shards for write and data size scaling• Add Slaves for read scaling (map-reduce) and redundancy• Sharding is Hard

Neat Snippets Replication Setup Sharding Setuphttps://github.com/mongodb/mongo-snippets

EC2 Notes• Reformat drive to EXT4 or XFS• Don’t use EBS for long term backups• Can use EBS for setting up replica sets

Mongo admin'ing

by Jesse Wolgamott on Apr 13, 2011

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Mongo admin’ing — Presentation Transcript