MongoDB的replica set架构是通过一个日志来存储写操作的，这个日志就叫做 oplog 。oplog.rs 是一个固定长度的 Capped Collection，它存在于local数据库中，用于记录replicaSets操作日志。在默认情况下，对于64位的MongoDB，oplog是比较大的，可以达到5%的磁盘空间，oplog的大小是可以通过mongod的参数 “ -oplogSize”来改变oplog的日志大小。
oplog内容样例：
> use local
> show collections
> db.oplog.rs.find()
新版有个问题，无法再像旧版一样直接操作了，必须先添加一个管理员用户，之后切换到管理员身份，再进行操作，具体可以见日志。
rs1:PRIMARY> show dbsshow dbs
2016-07-22T17:44:25.491+0800 E QUERY [thread1] Error: listDatabases failed:{
"ok" : 0,
"errmsg" : "not authorized on admin to execute command { listDatabases: 1.0 }",
"code" : 13
} :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
Mongo.prototype.getDBs@src/mongo/shell/mongo.js:62:1
shellHelper.show@src/mongo/shell/utils.js:761:19
shellHelper@src/mongo/shell/utils.js:651:15
@(shellhelp2):1:1
rs1:PRIMARY> use localuse local
switched to db local
rs1:PRIMARY> show collectionsshow collections
2016-07-22T17:44:40.317+0800 E QUERY [thread1] Error: listCollections failed: {
"ok" : 0,
"errmsg" : "not authorized on local to execute command { listCollections: 1.0, filter: {} }",
"code" : 13
} :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
DB.prototype._getCollectionInfosCommand@src/mongo/shell/db.js:773:1
DB.prototype.getCollectionInfos@src/mongo/shell/db.js:785:19
DB.prototype.getCollectionNames@src/mongo/shell/db.js:796:16
shellHelper.show@src/mongo/shell/utils.js:754:9
shellHelper@src/mongo/shell/utils.js:651:15
@(shellhelp2):1:1
rs1:PRIMARY> use adminuse admin
switched to db admin
rs1:PRIMARY> db.createUser(db.createUser(
... { {
... user: "bbb", user: "bbb",
... pwd: "bbb", pwd: "bbb",
... roles: [ { role: "root", db: "admin" } ] roles: [ { role: "root", db: "admin" } ]
... } }
... ) )
Successfully added user: {
"user" : "bbb",
"roles" : [
{
"role" : "root",
"db" : "admin"
}
]
}
rs1:PRIMARY> show dbsshow dbs
2016-07-22T17:45:54.756+0800 E QUERY [thread1] Error: listDatabases failed:{
"ok" : 0,
"errmsg" : "not authorized on admin to execute command { listDatabases: 1.0 }",
"code" : 13
} :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
Mongo.prototype.getDBs@src/mongo/shell/mongo.js:62:1
shellHelper.show@src/mongo/shell/utils.js:761:19
shellHelper@src/mongo/shell/utils.js:651:15
@(shellhelp2):1:1
rs1:PRIMARY> db.auth('bbb','bbb')db.auth('bbb','bbb')//此处认证过了才可以操作
1
rs1:PRIMARY> use localuse local
switched to db local
rs1:PRIMARY> show collectionsshow collections
me
oplog.rs
replset.election
startup_log
system.replset
rs1:PRIMARY> db.oplog.rs.find()db.oplog.rs.find()
{ "ts" : Timestamp(1469180416, 1), "h" : NumberLong("6313428569778261950"), "v" : 2, "op" : "n", "ns" : "", "o" : { "msg" : "initiating set" } }
{ "ts" : Timestamp(1469180428, 2), "t" : NumberLong(1), "h" : NumberLong("2174888517165095400"), "v" : 2, "op" : "n", "ns" : "", "o" : { "msg" : "new primary" } }
{ "ts" : Timestamp(1469180731, 1), "t" : NumberLong(1), "h" : NumberLong("-1515174104405674576"), "v" : 2, "op" : "c", "ns" : "admin.$cmd", "o" : { "create" : "system.version" } }
{ "ts" : Timestamp(1469180731, 2), "t" : NumberLong(1), "h" : NumberLong("7948077691112953460"), "v" : 2, "op" : "i", "ns" : "admin.system.version", "o" : { "_id" : "authSchema", "currentVersion" : 5 } }
{ "ts" : Timestamp(1469180731, 3), "t" : NumberLong(1), "h" : NumberLong("-9003778602149648332"), "v" : 2, "op" : "c", "ns" : "admin.$cmd", "o" : { "create" : "system.users" } }
{ "ts" : Timestamp(1469180731, 4), "t" : NumberLong(1), "h" : NumberLong("-5105507245190417325"), "v" : 2, "op" : "i", "ns" : "admin.system.users", "o" : { "_id" : "admin.bbb", "user" : "bbb", "db" : "admin", "credentials" : { "SCRAM-SHA-1" : { "iterationCount" : 10000, "salt" : "9hPZ67Nn1d9ZFSKfxfPmHw==", "storedKey" : "wbVBdAFG3tKPU0QwgoqA93XaSFY=", "serverKey" : "0FXoMrw01NIiYr8HNZ9p5mGhK8k=" } }, "roles" : [ { "role" : "root", "db" : "admin" } ] } }
rs1:PRIMARY>
查看master的oplog元数据信息：
> db.printReplicationInfo()
查看salve的同步状态：
> db.printSlaveReplicationInfo()
rs1:PRIMARY> db.printReplicationInfo()db.printReplicationInfo()
configured oplog size: 2124.869140625MB
log length start to end: 315secs (0.09hrs)
oplog first event time: Fri Jul 22 2016 17:40:16 GMT+0800 (CST)
oplog last event time: Fri Jul 22 2016 17:45:31 GMT+0800 (CST)
now: Fri Jul 22 2016 17:52:59 GMT+0800 (CST)
rs1:PRIMARY> db.printSlaveReplicationInfo() db.printSlaveReplicationInfo()
source: localhost:28011
syncedTo: Fri Jul 22 2016 17:45:31 GMT+0800 (CST)
0 secs (0 hrs) behind the primary
source: localhost:28012
syncedTo: Fri Jul 22 2016 17:45:31 GMT+0800 (CST)
0 secs (0 hrs) behind the primary
rs1:PRIMARY>