mongodb: replica set

setup 3 dbs

# mongod --rest --replSet myset
mongod --replSet myset --port 27017 --dbpath /data/db1
mongod --replSet myset --port 27018 --dbpath /data/db2
mongod --replSet myset --port 27019 --dbpath /data/db3

or set master config file:

dbpath = /data/db
#bind_ip = 127.0.0.1
port = 27017

#logpath = /var/log/mongodb.log

#logappend = true

master = true

replSet = myset

#nojournal = false

rest = true

and set slave config file:

dbpath = /data/db
#bind_ip = 127.0.0.1
port = 27017
#logpath = /var/log/mongodb.log
#logappend = true

replSet = myset

#nojournal = false

rest = true

slave = true

source = gambit:27017

* enter each's host name in your /etc/hosts file if you're using different hosts

-------------------------------------

initialize host replica set

# mongo --port 27017
> rs.initiate();


(http://www.mongodb.org/display/DOCS/Replica+Sets+-+Basics)
(http://www.kchodorow.com/blog/2010/07/30/replica-sets-part-1-master-slave-is-so-2009/)

got error couldn't initiate : can't find self in the replset config

supply config using localhost works!

> config = {_id: 'myset', members: [
    {_id: 0, host:'localhost:27017'},
    {_id: 1, host:'localhost:27018'},
    {_id: 2, host:'localhost:27019'}]
    }

> rs.initiate(config)


changing config

> config = {_id: 'myset', members: [
    {_id: 0, host:'192.168.1.10:27017'},
    {_id: 1, host:'192.168.1.9:27017'}]
    }

> rs.reconfig(config)


make query in slave available

> rs.slaveOk()


to create a cold standby set secondary as secondary-only

> config = rs.config()
> config.members[1].priority = 0
> rs.reconfig(config)


(http://docs.mongodb.org/manual/administration/replication-architectures/ )
(http://docs.mongodb.org/manual/core/replication/ )
(http://docs.mongodb.org/manual/reference/configuration-options/ )

(http://www.mongodb.org/display/DOCS/Replica+Set+Tutorial )
(http://www.mongodb.org/display/DOCS/Master+Slave )

-------------------------------------

restoring replication

clear local.* from new primary;
clear all /data/db files from new secondary;

restore from a primary fail

> config = {_id: 'myset', members: [
    {_id: 1, host:'localhost:27018'},
    {_id: 2, host:'localhost:27019'}]
    }

> rs.initiate(config)


got "errmsg" : "local.oplog.rs is not empty on the initiating member.  cannot initiate.",

> rs.reconfig(config, {force:1})


got "ok" : 1


point new secondary source to new primary

restore from a secondary fail

> config = {_id: 'myset', members: [
    {_id: 0, host:'localhost:27017'},
    {_id: 1, host:'localhost:27019'}]
    }

> rs.initiate(config)


got "errmsg" : "local.oplog.rs is not empty on the initiating member.  cannot initiate.",

> rs.reconfig(config, {force:1})


got "ok" : 1


* try copying files before restoration