Nosql Mongodb之旅(24)—MongoDB Replica Sets

发布时间：2020-12-13 13:46:00 所属栏目：百科来源：网络整理

导读：一、读写分离从库能进行查询，这样可以分担主库的大量的查询请求。 1、先向主库中插入一条测试数据 [plain] view plain copy [root@localhostbin]#./mongo--port28010 MongoDBshellversion:1.8.1 connectingto:127.0.0.1:28010/test rs1:PRIMARYdb.c1.inse

一、读写分离

从库能进行查询，这样可以分担主库的大量的查询请求。

1、先向主库中插入一条测试数据

[plain] 
    view plain 
    copy 
     
     
     
    
 [root@localhostbin]#./mongo--port28010
 MongoDBshellversion:1.8.1
 connectingto:127.0.0.1:28010/test
 rs1:PRIMARY>db.c1.insert({age:30})
 db.c2rs1:PRIMARY>db.c1.find()
 {"_id":ObjectId("4fc77f421137ea4fdb653b4a"),"age":30}

2、在从库中进行查询等操作

[root@localhostbin]#./mongo--port28011

connectingto:127.0.0.1:28011/test
rs1:SECONDARY>showcollections
ThuMay3122:27:17uncaughtexception:error:{"$err":"notmasterandslaveok=false",
"code":13435}
rs1:SECONDARY>

查询报错，说明是个从库且不能执行查询的操作

3、让从库可以读，分担主库的压力

rs1:SECONDARY>db.getMongo().setSlaveOk()

notmasterandslaveok=false
rs1:SECONDARY>showcollections
c1
system.indexes
rs1:SECONDARY>db.c1.find()
{"_id":ObjectId("4fc77f421137ea4fdb653b4a"),"age":30}
rs1:SECONDARY>

我们做到了。

二、故障转移

复制集比传统的Master-Slave 有改进的地方就是他可以进行故障的自动转移，如果我们停掉复制集中的一个成员，那么剩余成员会再自动选举出一个成员，做为主库，例如:我们将28010 这个主库停掉，然后再看一下复制集的状态

测试：

1、kill 28010端口的MongoDB

[root@localhostbin]#psaux|grepmongod

root67061.66.94633046168Sl21:490:26
/Apps/mongo/bin/mongod--replSetrs1--keyFile/data/key/r0--fork--port28010
root67330.46.74305286044?Sl21:500:06
/Apps/mongo/bin/mongod--replSetrs1--keyFile/data/key/r1--fork--port28011
root67470.44.74315484260?Sl21:500:06
/Apps/mongo/bin/mongod--replSetrs1--keyFile/data/key/r2--fork--port28012
root70190.00.75064684pts/2S+22:160:00grepmongod
[root@localhostbin]#kill-96706

2、再查看复制集状态

rs1:SECONDARY>rs.status()

{
"set":"rs1",
"date":ISODate("2012-05-31T14:17:03Z"),248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "myState":2,108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "members":[
{
"_id":0,248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "name":"localhost:28010",108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "health":0,248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "state":1,108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "stateStr":"(notreachable/healthy)",248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "uptime":0,108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "optime":{
"t":1338472279000,108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "i":1
},108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "optimeDate":ISODate("2012-05-31T13:51:19Z"),248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "lastHeartbeat":ISODate("2012-05-31T14:16:42Z"),108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "errmsg":"socketexception"
"_id":1,108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "name":"localhost:28011",248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "health":1,108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "state":2,248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "stateStr":"SECONDARY",248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "self":true
},108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "_id":2,248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "name":"localhost:28012",108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "health":1,108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "stateStr":"PRIMARY",248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "uptime":1528,248); line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "lastHeartbeat":ISODate("2012-05-31T14:17:02Z")
}
],108); list-style:decimal-leading-zero outside; color:inherit; line-height:21px; margin:0px!important; padding:0px 3px 0px 10px!important"> "ok":1
}
rs1:SECONDARY>

"stateStr":"(notreachable/healthy)",

可以看到28010 这个端口的MongoDB 出现了异常，而系统自动选举了28012 这个端口为主，所以这样的故障处理机制，能将系统的稳定性大大提高。

（编辑：李大同）

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