绝好的MongoDB学习资料之八. Replication (2)

2. Master/Slave Master/Slave 是一种典型的备份方案，MongoDB 支持 One Master Multi Salver 和 Multi Master One Slave 等多种部署方式。 先从简单的 镜像备份 开始。 $ sudo mkdir -p /var/mongodb/0$ sudo mkdir -p /var/mongodb/1$ sudo ./mongod –for

2. Master/Slave

Master/Slave 是一种典型的备份方案，MongoDB 支持 “One Master Multi Salver” 和 “Multi Master One Slave” 等多种部署方式。

先从简单的 “镜像备份” 开始。

$ sudo mkdir -p /var/mongodb/0$ sudo mkdir -p /var/mongodb/1$ sudo ./mongod --fork --logpath /dev/null --dbpath /var/mongodb/0 --masterforked process: 1388all output going to: /dev/null$ sudo ./mongod --fork --logpath /dev/null --dbpath /var/mongodb/1 --port 27018 --slave --source localhost:27017 --autoresyncforked process: 1401all output going to: /dev/null

autoresync 参数会在系统发生意外情况造成主从数据不同步时，自动启动复制操作 (同步复制 10 分钟内仅执行一次)。除此之外，还可以用 –slavedelay 设定更新频率(秒)。

使用 isMaster、printReplicationInfo、printSlaveReplicationInfo 等命令获取相关状态信息。

$ ./mongo > db.isMaster(){ "ismaster" : true, "ok" : 1 }> db.printReplicationInfo()configured oplog size:   990MBlog length start to end: 1164secs (0.32hrs)oplog first event time:  Mon Aug 23 2010 12:23:54 GMT+0800 (CST)oplog last event time:   Mon Aug 23 2010 12:43:18 GMT+0800 (CST)now:                     Mon Aug 23 2010 12:43:24 GMT+0800 (CST)$ ./mongo localhost:27018> db.isMaster(){ "ismaster" : false, "ok" : 1 }> db.printSlaveReplicationInfo()source:   localhost:27017         syncedTo: Mon Aug 23 2010 12:43:58 GMT+0800 (CST)                 = 10secs ago (0hrs)> show dbsadminlocaltest> use localswitched to db local> show collectionsmepair.syncsourcessystem.indexes> db.sources.find(){ "_id" : ObjectId("4c71f8178d806ad3f54dd89a"), "host" : "localhost:27017", "source" : "main", "syncedTo" : { "t" : 1282538738000, "i" : 1 }, "localLogTs" : { "t" : 0, "i" : 0 } }

Slave 的配置信息保存在 local.sources 中。

通常我们会使用主从方案实现读写分离，但需要设置 Slave_OK。

$ ipythonIPython 0.10 -- An enhanced Interactive Python.In [1]: from pymongo import *In [2]: m_conn = Connection()In [3]: s_conn = Connection(host="localhost:27018", slave_okay=True)In [4]: m_db = m_conn.testIn [5]: s_db = s_conn.test# ----------------------------------------- #In [6]: m_db.users.insert({"name":"user3"})Out[6]: ObjectId('4c71feb0499b140632000000')In [7]: s_db.users.find_one({"name":"user3"}) # 数据被复制到 SlaveOut[7]: {u'_id': ObjectId('4c71feb0499b140632000000'), u'name': u'user3'}In [8]: m_db.users.remove({"name":"user3"}) # 删除 Master 数据In [9]: for u in m_db.users.find(): print u   ....:{u'_id': ObjectId('4c71fa4d5e01e1ba6d62398f'), u'name': u'user1'}In [10]: for u in s_db.users.find(): print u # Slave 记录被同步删除   ....:{u'_id': ObjectId('4c71fa4d5e01e1ba6d62398f'), u'name': u'user1'}# ----------------------------------------- #In [11]: s_db.users.insert({"name":"userx"}) # 在 Slave 插入数据Out[11]: ObjectId('4c71ff2c499b140632000001')In [12]: for u in m_db.users.find(): print u # Master 上无该数据   ....:{u'_id': ObjectId('4c71fa4d5e01e1ba6d62398f'), u'name': u'user1'}In [13]: for u in s_db.users.find(): print u # Slave 同样没有   ....:{u'_id': ObjectId('4c71fa4d5e01e1ba6d62398f'), u'name': u'user1'}

可见 Slave 读操作正常，但写无效果。

我们还可以部署 “One Slave Two Master” 方案。

$ sudo mkdir -p /var/mongodb/m1$ sudo mkdir -p /var/mongodb/m2$ sudo mkdir -p /var/mongodb/s$ sudo ./mongod --fork --dbpath /var/mongodb/m1 --logpath /dev/null --masterforked process: 1616all output going to: /dev/null$ sudo ./mongod --fork --dbpath /var/mongodb/m2 --logpath /dev/null --port 27018 --masterforked process: 1627all output going to: /dev/null$ sudo ./mongod --fork --dbpath /var/mongodb/s --logpath /dev/null --port 27019 --slaveforked process: 1638all output going to: /dev/null

连接 Slave，添加配置。

$ ./mongo localhost:27019MongoDB shell version: 1.6.1connecting to: localhost:2701<mark style="color:transparent">本文来源gaodaimacom搞#^代%!码网@</mark>9/test> use localswitched to db local> db.sources.insert({host:"localhost:27017"})> db.sources.insert({host:"localhost:27018"})> db.printSlaveReplicationInfo()source:   localhost:27017         syncedTo: Mon Aug 23 2010 13:06:03 GMT+0800 (CST)                 = 17secs ago (0hrs)source:   localhost:27018         doing initial sync

在两台 Master 上添加数据，查看复制效果。

$ ./mongo localhost:27017MongoDB shell version: 1.6.1connecting to: localhost:27017/test> use db1switched to db db1> db.users.insert({name:"user1"})> db.users.insert({name:"user2"})> db.users.find(){ "_id" : ObjectId("4c720211ade34e85c5380eab"), "name" : "user1" }{ "_id" : ObjectId("4c720214ade34e85c5380eac"), "name" : "user2" }> exitbye

$ ./mongo localhost:27018MongoDB shell version: 1.6.1connecting to: localhost:27018/test> use db2switched to db db2> db.blogs.insert({title:"aaa"})> db.blogs.insert({title:"bbb"})> db.blogs.insert({title:"ccc"})> db.blogs.find(){ "_id" : ObjectId("4c720236f24118cb2f59218d"), "title" : "aaa" }{ "_id" : ObjectId("4c720239f24118cb2f59218e"), "title" : "bbb" }{ "_id" : ObjectId("4c72023cf24118cb2f59218f"), "title" : "ccc" }> exitbye

$ ./mongo localhost:27019MongoDB shell version: 1.6.1connecting to: localhost:27019/test> show dbsadmindb1db2local> use db1switched to db db1> db.users.find(){ "_id" : ObjectId("4c720211ade34e85c5380eab"), "name" : "user1" }{ "_id" : ObjectId("4c720214ade34e85c5380eac"), "name" : "user2" }> use db2switched to db db2> db.blogs.find(){ "_id" : ObjectId("4c720236f24118cb2f59218d"), "title" : "aaa" }{ "_id" : ObjectId("4c720239f24118cb2f59218e"), "title" : "bbb" }{ "_id" : ObjectId("4c72023cf24118cb2f59218f"), "title" : "ccc" }>

一切正常。

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