![Command Line--master [--oplogSize <MB>]--slave –source <host> [--only <db>]](https://image.slidesharecdn.com/mongodbreplicationmongosfapr20101-100430191028-phpapp02/85/MongoDB-Replication-Dwight-Merriman-3-320.jpg)
MongoDB Replication (Dwight Merriman)
- 1. Replication and MongoDBDwight Merriman (@dmerr)10gen
- 2. BasicsA bit like MySQL replicationAsynchronous master/slaveLet’s try it…
- 3. Command Line--master [--oplogSize <MB>]--slave –source <host> [--only <db>]
- 4. The local dbDoesn’t replicateOn master:local.oplog.$mainlocal.slavesOn slave:local.sources > use local > db.sources.find()
- 5. Administration> // master> use local> db.printReplicationInfo()> db.slaves.find()> db.oplog.$main.findOne()// slave> use local> db.printSlaveReplicationInfo()
- 6. TopologiesM->SM->S ->S ->SM->SM-/M<->M *very restrictive
- 8. Replica PairsReplica Sets A cluster of N servers
- 9. Any (one) node can be primary
- 10. Consensus election of primary
- 13. All writes to primary
- 14. Reads can be to primary or a second
- 15. Rack and data center aware
- 16. ETA: v1.6 July 2010 (“stable”)Replica Sets – Design ConceptsA write is only truly committed once it has replicated to a majority of servers in the set. (We can wait for confirmation for this though, with getLastError.)Writes which are committed at the master of the set may be visible before the true cluster-wide commit has occurred. This property, which is more relaxed than some traditional products, makes theoretically achievable performance and availability higher.On a failover, if there is data which has not replicated form the primary, the data is dropped (see #1).
- 17. A SetMember 1Member 3Member 2
- 18. A SetMember 1Member 3Member 2PRIMARY
- 19. A SetMember 1Member 3PRIMARYMember 2DOWN
- 20. A SetMember 1Member 3PRIMARYMember 2RECOVER-ING
- 21. A SetMember 1Member 3PRIMARYMember 2
- 22. Configuration{ _id : <setname>, members: [ { _id : <ordinal>, host : <hostname[:port]>, [, priority: <priority>] [, arbiterOnly : true] [, votes : n] } , ... ], settings: { [heartbeatSleep : <seconds>] [, heartbeatTimeout : <seconds>] [, heartbeatConnRetries : <n>] [, getLastErrorDefaults: <lasterrdefaults>] }}
- 23. Initiation> cfg = {... _id : "acme_a",... members : [... { _id : 0, host : "sf1.acme.com" },... { _id : 1, host : "sf2.acme.com" },... { _id : 2, host : "sf3.acme.com" } ] }> use admin> db.runCommand({replSetInitiate:cfg})
- 24. Commands{ isMaster : 1 } Checks if the node to which we are connecting is currently primary. Most drivers do this check automatically and then send requires to the current primary.{ replSetGetStatus : 1 } Status information on the replica set from this node's point of view.http://localhost:28017/replSetGetStatus?text{ replSetInitiate : <config> } Initiate a replica set. { replSetFreeze : <bool> } Freezing a replica set prevents failovers from occurring. This can be useful during maintenance.
- 25. Set Member TypesNormalDR (priority < 1.0)Passive (priority == 0)Arbiter (no data, but can vote)
- 26. With Sharding
- 27. Docs: http://www.mongodb.org/display/DOCS/Replica+SetsQuestions?Email [email protected] if you would like to be a replica set beta tester.10gen is hiring.