MongoDB复制集是一个带有故障转移的主从集群。是从现有的主从模式演变而来，增加了自动故障转移和节点成员自动恢复。
MongoDB复制集模式中没有固定的主结点，在启动后，多个服务节点间将自动选举产生一个主结点。该主结点被称为primary，一个或多个从结点被称为secondaries。
primary结点基本上就是master结点，不同之处在于primary结点在不同时间可能是不同的服务器。如果当前的主结点失效了，复制集中的其余结点将会试图选出一个
新的主结点。
MongoDB复制集模式的好处：
- 一切自动化。首先，复制集模式本身做了大量的管理工作，自动管理从节点，确保数据不会不一致。
- 主节点挂掉后，会自动判断集群中的服务器并进行故障转移，推举新的主节点。
- 一个复制集集群支持1-7台服务器，在一个复制集中各个服务器数据保持完全一致。
在一个MongoDB复制集集群中，各个服务器有以下几种状态：
- Primary 主节点，一个复制集有且仅有一台服务器处于Primary状态，只有主节点才对外提供读写服务。如果主节点挂掉，复制集将投票选出一个备节点成为新的主节点。
- Secondary 备用节点，复制集允许有多台Secondary，每个备用节点的数据与主节点的数据是完全同步的。Recovering 恢复中，当复制集中某台服务器挂掉或者掉线后数据无法同步，重新恢复服务后从其他成员复制数据，这时就处于恢复过程，数据同步后，该节点又回到备用状态。
- Arbiter 仲裁节点，该类节点可以不用单独存在，如果配置为仲裁节点，就主要负责在复本集中监控其他节点状态，投票选出主节点。该节点将不会用于存放数据。如果没有仲裁节点，那么投票工作将由所有节点共同进行。
- Down 无效节点，当服务器挂掉或掉线时就会处于该状态。复制集的从节点读请求，也是在各个Driver层设置slaveOk的值来实现的。
如上介绍所知，mongodb中的复制可以在多台服务器中同步数据。复制提供了冗余和增加了数据的高可用性，防止单个节点易丢失数据的可能性，也可以用来进行读写分离提高客户端操作性能。复制集中各节点的mongodb实例有相同的数据集副本。主节点可以接收客户端所有写操作记录到日志中，从库复制主库的操作日志记录应用到其数据库中。一个客户端只能有一个主节点，如果主节点不可用（10秒内无法连接），复制集中将选一个成员节点作为主节点。
mongodb主备+仲裁的基本结构如下：
下面简单介绍下MongoDB 副本集的部署过程：
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1）服务器信息
sign-mongo01.wangshibo.cn 172.16.51.216 Primary
sign-mongo02.wangshibo.cn 172.16.51.217 Secondary
sign-mongo03.wangshibo.cn 172.16.51.218 Arbiter
三台服务器均设置好主机名，关闭iptables及selinux（略）
2）在3台服务器文件hosts文件中都添加以下3行：
[root@sign-mongo01 ~]
# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.51.216 sign-mongo01.wangshibo.cn
172.16.51.217 sign-mongo02.wangshibo.cn
172.16.51.218 sign-mongo03.wangshibo.cn
3）安装部署mongodb（三台机器都安装）
下载地址：https:
//www
.mongodb.org
/dl/linux/x86_64-rhel62
[app@sign-mongo01 software]$
pwd
/data/software
[app@sign-mongo01 software]$
ls
mongodb-linux-x86_64-rhel62-v3.2-latest.tgz
[app@sign-mongo01 software]$
tar
-zvxf mongodb-linux-x86_64-rhel62-v3.2-latest.tgz
[app@sign-mongo01 software]$
mv
mongodb-linux-x86_64-rhel62-3.2.17-34-g4c1bae566c
/data/mongodb
[app@sign-mongo01 software]$
cd
/data/mongodb/
[app@sign-mongo01 mongodb]$
mkdir
data
[app@sign-mongo01 mongodb]$
mkdir
log
[app@sign-mongo01 mongodb]$ vim mongodb.conf
pidfilepath=
/data/mongodb/log/mongod
.pid
logpath=
/data/mongodb/log/mongod
.log
dbpath=
/data/mongodb
logappend=
true
bind_ip=172.16.51.216
port=27017
fork=
true
replSet=rs0
备节点的mongodb.conf配置文件分别为：
[app@sign-mongo02 mongodb]$ vim mongodb.conf
pidfilepath=
/data/mongodb/log/mongod
.pid
logpath=
/data/mongodb/log/mongod
.log
dbpath=
/data/mongodb
logappend=
true
bind_ip=172.16.51.217
port=27018
fork=
true
replSet=rs0
其中：replSet=rs0
#表示复制集名称：rs0
启动主备服务器的mongodb
[app@sign-mongo01 ~]$
/data/mongodb/bin/mongod
--config
/data/mongodb/mongodb
.conf
about to fork child process, waiting
until
server is ready
for
connections.
forked process: 7317
child process started successfully, parent exiting
[app@sign-mongo01 mongodb]$
ps
-ef|
grep
mongodb
app 7317 1 0 21:38 ? 00:00:00
/data/mongodb/bin/mongod
--config
/data/mongodb/mongodb
.conf
app 7342 7254 0 21:38 pts
/1
00:00:00
grep
mongodb
[app@sign-mongo01 mongodb]$
lsof
-i:27017
COMMAND PID USER FD TYPE DEVICE SIZE
/OFF
NODE NAME
mongod 7317 app 6u IPv4 27011 0t0 TCP sign-mongo01.wangshibo.cn:27017 (LISTEN)
[app@sign-mongo02 mongodb]$
/data/mongodb/bin/mongod
--config
/data/mongodb/mongodb
.conf
about to fork child process, waiting
until
server is ready
for
connections.
forked process: 9725
child process started successfully, parent exiting
[app@sign-mongo02 mongodb]$
lsof
-i:27018
COMMAND PID USER FD TYPE DEVICE SIZE
/OFF
NODE NAME
mongod 9725 app 6u IPv4 27191 0t0 TCP sign-mongo02.wangshibo.cn:27018 (LISTEN)
设置mongodb的环变量
[root@sign-mongo01 src]
# vim /etc/profile
......
export
PATH=$PATH:
/data/mongodb/bin
[root@sign-mongo01 src]
# source /etc/profile
登录到mongodb中：
[app@sign-mongo01 ~]$ mongo 172.16.51.216:27017
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.216:27017
/test
Welcome to the MongoDB shell.
For interactive help,
type
"help"
.
For
more
comprehensive documentation, see
http:
//docs
.mongodb.org/
Questions? Try the support group
http:
//groups
.google.com
/group/mongodb-user
Server has startup warnings:
2017-11-22T21:38:18.063+0800 I CONTROL [initandlisten]
2017-11-22T21:38:18.063+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/enabled
is
'always'
.
2017-11-22T21:38:18.063+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:38:18.063+0800 I CONTROL [initandlisten]
2017-11-22T21:38:18.063+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/defrag
is
'always'
.
2017-11-22T21:38:18.063+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:38:18.063+0800 I CONTROL [initandlisten]
>
初始化复制集：（集合为：
"rs0"
；第一个成员为：
"sign-mongo01.wangshibo.cn:27017"
> rs.initiate({_id:
"rs0"
,members: [{ _id: 0 , host:
"sign-mongo01.wangshibo.cn:27017"
}]})
{
"ok"
: 1 }
rs0:OTHER>
//
接着回车，显示这个节点为Primary主节点
rs0:PRIMARY>
接着添加另1个成员：
rs0:PRIMARY> rs.add(
"sign-mongo02.wangshibo.cn:27018"
)
{
"ok"
: 1 }
查看成员信息 （或者使用 db.isMaster() ）
rs0:PRIMARY> rs.status()
{
"set"
:
"rs0"
,
"date"
: ISODate(
"2017-11-22T13:55:28.446Z"
),
"myState"
: 1,
"term"
: NumberLong(1),
"heartbeatIntervalMillis"
: NumberLong(2000),
"members"
: [
{
"_id"
: 0,
"name"
:
"sign-mongo01.wangshibo.cn:27017"
,
"health"
: 1,
"state"
: 1,
"stateStr"
:
"PRIMARY"
,
"uptime"
: 1031,
"optime"
: {
"ts"
: Timestamp(1511358895, 1),
"t"
: NumberLong(1)
},
"optimeDate"
: ISODate(
"2017-11-22T13:54:55Z"
),
"infoMessage"
:
"could not find member to sync from"
,
"electionTime"
: Timestamp(1511358843, 2),
"electionDate"
: ISODate(
"2017-11-22T13:54:03Z"
),
"configVersion"
: 2,
"self"
:
true
},
{
"_id"
: 1,
"name"
:
"sign-mongo02.wangshibo.cn:27018"
,
"health"
: 1,
"state"
: 2,
"stateStr"
:
"SECONDARY"
,
"uptime"
: 32,
"optime"
: {
"ts"
: Timestamp(1511358895, 1),
"t"
: NumberLong(1)
},
"optimeDate"
: ISODate(
"2017-11-22T13:54:55Z"
),
"lastHeartbeat"
: ISODate(
"2017-11-22T13:55:27.684Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-22T13:55:27.827Z"
),
"pingMs"
: NumberLong(0),
"configVersion"
: 2
}
],
"ok"
: 1
}
或者使用该方法查看，结果也是一样：
rs0:PRIMARY> use admin
switched to db admin
rs0:PRIMARY> db.runCommand( { replSetGetStatus : 1 } )
{
"set"
:
"rs0"
,
"date"
: ISODate(
"2017-11-23T01:12:20.701Z"
),
"myState"
: 1,
"term"
: NumberLong(1),
"heartbeatIntervalMillis"
: NumberLong(2000),
"members"
: [
{
"_id"
: 0,
"name"
:
"sign-mongo01.wangshibo.cn:27017"
,
"health"
: 1,
"state"
: 1,
"stateStr"
:
"PRIMARY"
,
"uptime"
: 41643,
"optime"
: {
"ts"
: Timestamp(1511358895, 1),
"t"
: NumberLong(1)
},
"optimeDate"
: ISODate(
"2017-11-22T13:54:55Z"
),
"electionTime"
: Timestamp(1511358843, 2),
"electionDate"
: ISODate(
"2017-11-22T13:54:03Z"
),
"configVersion"
: 2,
"self"
:
true
},
{
"_id"
: 1,
"name"
:
"sign-mongo02.wangshibo.cn:27018"
,
"health"
: 1,
"state"
: 2,
"stateStr"
:
"SECONDARY"
,
"uptime"
: 40645,
"optime"
: {
"ts"
: Timestamp(1511358895, 1),
"t"
: NumberLong(1)
},
"optimeDate"
: ISODate(
"2017-11-22T13:54:55Z"
),
"lastHeartbeat"
: ISODate(
"2017-11-23T01:12:19.418Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-23T01:12:16.225Z"
),
"pingMs"
: NumberLong(0),
"configVersion"
: 2
}
],
"ok"
: 1
}
rs0:PRIMARY>
详细说明如下：
"_id"
:
#集群中节点编号
"name"
:
#成员服务器名称及端口
"health"
:
#表示成员中的健康状态（0:down;1:up）
"state"
:
#为0~10，表示成员的当前状态
"stateStr"
:
#描述该成员是主库（PRIMARY）还是备库（SECONDARY）
"uptime"
:
#该成员在线时间（秒）
"optime"
:
#成员最后一次应用日志(oplog)的信息
"optimeDate"
:
#成员最后一次应用日志(oplog)的时间
"electionTime"
:
#当前primary从操作日志中选举信息
"electionDate"
:
#当前primary被选定为primary的日期
"configVersion"
:
#mongodb版本
"self"
:
#为true 表示当前节点
4）测试操作。在主库中，可以任意操作：
rs0:PRIMARY> show dbs
local
0.000GB
rs0:PRIMARY> use mydb
//
切换到要创建的数据库
switched to db mydb
rs0:PRIMARY> show dbs
//use
只是转到相关数据库，此时并没有做任何操作，所以并不会创建相应的数据库，只有当真正的操作了一次数据库就会自动创建。
local
0.000GB
rs0:PRIMARY> db.stats();
{
"db"
:
"mydb"
,
"collections"
: 0,
"objects"
: 0,
"avgObjSize"
: 0,
"dataSize"
: 0,
"storageSize"
: 0,
"numExtents"
: 0,
"indexes"
: 0,
"indexSize"
: 0,
"fileSize"
: 0,
"ok"
: 1
}
rs0:PRIMARY> db.coll.insert({
"id"
:1})
WriteResult({
"nInserted"
: 1 })
rs0:PRIMARY> db.coll.
find
()
{
"_id"
: ObjectId(
"5a162222991b83743942d169"
),
"id"
: 1 }
rs0:PRIMARY> db.coll.remove({
"id"
:1})
WriteResult({
"nRemoved"
: 1 })
rs0:PRIMARY> show dbs
local
0.000GB
mydb 0.000GB
现在到备库中
172.16.51.217 （sign-mongo02.wangshibo.cn ）
查看分库数据库目录，发现多了数据库，数据库与主库（172.16.51.216）一致！是主库同步过来的。
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.217:27018
/test
Server has startup warnings:
2017-11-22T21:46:38.417+0800 I CONTROL [initandlisten]
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/enabled
is
'always'
.
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten]
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/defrag
is
'always'
.
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten]
在副本服务器中登录其本地数据库，发现可以连接，但是无法读写操作：
rs0:SECONDARY> show dbs
2017-11-23T09:25:35.961+0800 E QUERY [thread1] Error: listDatabases failed:{
"ok"
: 0,
"errmsg"
:
"not master and slaveOk=false"
,
"code"
: 13435 } :
_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:781:19
shellHelper@src
/mongo/shell/utils
.js:671:15
@(shellhelp2):1:1
rs0:SECONDARY>
从库开启读操作（此时可以测试主库插入，从库查看，同步正常）：
rs0:SECONDARY> rs.slaveOk();
rs0:SECONDARY> show dbs
local
0.000GB
mydb 0.000GB
5）现在模拟主库不可用，将主节点服务停止：
[app@sign-mongo01 mongodb]$ pkill -9 mongod
[app@sign-mongo01 mongodb]$
ps
-ef|
grep
mongodb
app 9524 9398 0 09:32 pts
/0
00:00:00
grep
mongodb
到备节点172.16.51.217 中登录mongodb，查看复制集状态：
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.217:27018
/test
Server has startup warnings:
2017-11-22T21:46:38.417+0800 I CONTROL [initandlisten]
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/enabled
is
'always'
.
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten]
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/defrag
is
'always'
.
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten]
rs0:SECONDARY> rs.status()
{
"set"
:
"rs0"
,
"date"
: ISODate(
"2017-11-23T01:33:29.688Z"
),
"myState"
: 2,
"term"
: NumberLong(1),
"heartbeatIntervalMillis"
: NumberLong(2000),
"members"
: [
{
"_id"
: 0,
"name"
:
"sign-mongo01.wangshibo.cn:27017"
,
"health"
: 0,
"state"
: 8,
"stateStr"
:
"(not reachable/healthy)"
,
"uptime"
: 0,
"optime"
: {
"ts"
: Timestamp(0, 0),
"t"
: NumberLong(-1)
},
"optimeDate"
: ISODate(
"1970-01-01T00:00:00Z"
),
"lastHeartbeat"
: ISODate(
"2017-11-23T01:33:28.732Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-23T01:32:28.099Z"
),
"pingMs"
: NumberLong(0),
"lastHeartbeatMessage"
:
"Connection refused"
,
"configVersion"
: -1
},
{
"_id"
: 1,
"name"
:
"sign-mongo02.wangshibo.cn:27018"
,
"health"
: 1,
"state"
: 2,
"stateStr"
:
"SECONDARY"
,
"uptime"
: 42412,
"optime"
: {
"ts"
: Timestamp(1511399985, 1),
"t"
: NumberLong(1)
},
"optimeDate"
: ISODate(
"2017-11-23T01:19:45Z"
),
"infoMessage"
:
"could not find member to sync from"
,
"configVersion"
: 2,
"self"
:
true
}
],
"ok"
: 1
}
有上面可看出，主节点删除服务进程，primary并没有切换到备节点上：
再次启动主节点的mongodb服务，发现primary才自动切换回到主节点：
[app@sign-mongo01 mongodb]$
nohup
/data/mongodb/bin/mongod
--config
/data/mongodb/mongodb
.conf
nohup
: ignoring input and appending output to `
nohup
.out'
[app@sign-mongo01 mongodb]$
ps
-ef|
grep
mongodb
app 9538 1 8 09:37 ? 00:00:00
/data/mongodb/bin/mongod
--config
/data/mongodb/mongodb
.conf
app 9610 9398 0 09:37 pts
/0
00:00:00
grep
mongodb
[app@sign-mongo01 mongodb]$ mongo 172.16.51.216:27017
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.216:27017
/test
Server has startup warnings:
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten]
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/enabled
is
'always'
.
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten]
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/defrag
is
'always'
.
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten]
rs0:PRIMARY> rs.status()
{
"set"
:
"rs0"
,
"date"
: ISODate(
"2017-11-23T01:38:19.631Z"
),
"myState"
: 1,
"term"
: NumberLong(2),
"heartbeatIntervalMillis"
: NumberLong(2000),
"members"
: [
{
"_id"
: 0,
"name"
:
"sign-mongo01.wangshibo.cn:27017"
,
"health"
: 1,
"state"
: 1,
"stateStr"
:
"PRIMARY"
,
"uptime"
: 54,
"optime"
: {
"ts"
: Timestamp(1511401058, 2),
"t"
: NumberLong(2)
},
"optimeDate"
: ISODate(
"2017-11-23T01:37:38Z"
),
"infoMessage"
:
"could not find member to sync from"
,
"electionTime"
: Timestamp(1511401058, 1),
"electionDate"
: ISODate(
"2017-11-23T01:37:38Z"
),
"configVersion"
: 2,
"self"
:
true
},
{
"_id"
: 1,
"name"
:
"sign-mongo02.wangshibo.cn:27018"
,
"health"
: 1,
"state"
: 2,
"stateStr"
:
"SECONDARY"
,
"uptime"
: 53,
"optime"
: {
"ts"
: Timestamp(1511401058, 2),
"t"
: NumberLong(2)
},
"optimeDate"
: ISODate(
"2017-11-23T01:37:38Z"
),
"lastHeartbeat"
: ISODate(
"2017-11-23T01:38:18.072Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-23T01:38:18.596Z"
),
"pingMs"
: NumberLong(0),
"syncingTo"
:
"sign-mongo01.wangshibo.cn:27017"
,
"configVersion"
: 2
}
],
"ok"
: 1
}
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
现在开始部署仲裁节点sign-mongo03.wangshibo.cn
[app@sign-mongo03 ~]$
mkdir
/data/mongodb/arbiter
[app@sign-mongo03 ~]$ ll -d
/data/mongodb/arbiter
drwxrwxr-x 2 app app 4096 Nov 23 09:39
/data/mongodb/arbiter
本案例是在普通用户app账号下部署的，权限都是app.app。
如果是在root账号下部署，那么需要将mongodb数据目录下的文件全部设置mongodb.mongodb权限
mongodb.conf配置：
[app@sign-mongo03 ~]$ vim
/data/mongodb/mongodb
.conf
pidfilepath=
/data/mongodb/log/mongod
.pid
logpath=
/data/mongodb/log/mongod
.log
dbpath=
/data/mongodb/arbiter
logappend=
false
bind_ip=172.16.51.218
port=27019
fork=
true
replSet=rs0
接着重启服务：
[app@sign-mongo03 ~]$
/data/mongodb/bin/mongod
--config
/data/mongodb/mongodb
.conf
about to fork child process, waiting
until
server is ready
for
connections.
forked process: 9217
child process started successfully, parent exiting
[app@sign-mongo03 ~]$
ps
-ef|
grep
mongo
app 9217 1 1 09:46 ? 00:00:00
/data/mongodb/bin/mongod
--config
/data/mongodb/mongodb
.conf
app 9242 9158 0 09:46 pts
/0
00:00:00
grep
mongo
[app@sign-mongo03 ~]$
lsof
-i:27019
COMMAND PID USER FD TYPE DEVICE SIZE
/OFF
NODE NAME
mongod 9217 app 6u IPv4 37321 0t0 TCP sign-mongo03.wangshibo.cn:27019 (LISTEN)
然后在Paimary主节点sign-mongo01.wangshibo.cn的mongodb中添加仲裁节点并查看结果
[app@sign-mongo01 mongodb]$ mongo 172.16.51.216:27017
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.216:27017
/test
Server has startup warnings:
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten]
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/enabled
is
'always'
.
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten]
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/defrag
is
'always'
.
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-23T09:37:26.467+0800 I CONTROL [initandlisten]
rs0:PRIMARY> rs.addArb(
"sign-mongo03.wangshibo.cn:27019"
)
{
"ok"
: 1 }
rs0:PRIMARY> db.isMaster()
{
"hosts"
: [
"sign-mongo01.wangshibo.cn:27017"
,
"sign-mongo02.wangshibo.cn:27018"
],
"arbiters"
: [
"sign-mongo03.wangshibo.cn:27019"
],
"setName"
:
"rs0"
,
"setVersion"
: 4,
"ismaster"
:
true
,
"secondary"
:
false
,
"primary"
:
"sign-mongo01.wangshibo.cn:27017"
,
"me"
:
"sign-mongo01.wangshibo.cn:27017"
,
"electionId"
: ObjectId(
"7fffffff0000000000000003"
),
"maxBsonObjectSize"
: 16777216,
"maxMessageSizeBytes"
: 48000000,
"maxWriteBatchSize"
: 1000,
"localTime"
: ISODate(
"2017-11-23T01:59:03.554Z"
),
"maxWireVersion"
: 4,
"minWireVersion"
: 0,
"ok"
: 1
}
rs0:PRIMARY> rs.status()
{
"set"
:
"rs0"
,
"date"
: ISODate(
"2017-11-23T02:00:26.312Z"
),
"myState"
: 1,
"term"
: NumberLong(3),
"heartbeatIntervalMillis"
: NumberLong(2000),
"members"
: [
{
"_id"
: 0,
"name"
:
"sign-mongo01.wangshibo.cn:27017"
,
"health"
: 1,
"state"
: 1,
"stateStr"
:
"PRIMARY"
,
"uptime"
: 368,
"optime"
: {
"ts"
: Timestamp(1511402420, 1),
"t"
: NumberLong(3)
},
"optimeDate"
: ISODate(
"2017-11-23T02:00:20Z"
),
"electionTime"
: Timestamp(1511402069, 1),
"electionDate"
: ISODate(
"2017-11-23T01:54:29Z"
),
"configVersion"
: 5,
"self"
:
true
},
{
"_id"
: 1,
"name"
:
"sign-mongo02.wangshibo.cn:27018"
,
"health"
: 1,
"state"
: 2,
"stateStr"
:
"SECONDARY"
,
"uptime"
: 367,
"optime"
: {
"ts"
: Timestamp(1511402420, 1),
"t"
: NumberLong(3)
},
"optimeDate"
: ISODate(
"2017-11-23T02:00:20Z"
),
"lastHeartbeat"
: ISODate(
"2017-11-23T02:00:26.306Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-23T02:00:26.309Z"
),
"pingMs"
: NumberLong(0),
"syncingTo"
:
"sign-mongo01.wangshibo.cn:27017"
,
"configVersion"
: 5
},
{
"_id"
: 3,
"name"
:
"sign-mongo03.wangshibo.cn:27019"
,
"health"
: 1,
"state"
: 7,
"stateStr"
:
"ARBITER"
,
"uptime"
: 93,
"lastHeartbeat"
: ISODate(
"2017-11-23T02:00:26.306Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-23T02:00:25.306Z"
),
"pingMs"
: NumberLong(0),
"configVersion"
: 5
}
],
"ok"
: 1
}
至此，添加完成！！
再次测试主备切换。关闭172.16.51.216（primary）中删除服务进程：
[app@sign-mongo01 mongodb]$ pkill -9 mongod
[app@sign-mongo01 mongodb]$
ps
-ef|
grep
mongod
app 9664 9398 0 09:50 pts
/0
00:00:00
grep
mongod
[app@sign-mongo01 mongodb]$
lsof
-i:27017
[app@sign-mongo01 mongodb]$
然后到172.16.51.217:27018（secondary）查看，发现primary已经切换为172.16.51.217
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.217:27018
/test
Server has startup warnings:
2017-11-22T21:46:38.417+0800 I CONTROL [initandlisten]
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/enabled
is
'always'
.
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten]
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/defrag
is
'always'
.
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-22T21:46:38.418+0800 I CONTROL [initandlisten]
rs0:PRIMARY> rs.status()
{
"set"
:
"rs0"
,
"date"
: ISODate(
"2017-11-23T02:01:17.762Z"
),
"myState"
: 1,
"term"
: NumberLong(4),
"heartbeatIntervalMillis"
: NumberLong(2000),
"members"
: [
{
"_id"
: 0,
"name"
:
"sign-mongo01.wangshibo.cn:27017"
,
"health"
: 0,
"state"
: 8,
"stateStr"
:
"(not reachable/healthy)"
,
"uptime"
: 0,
"optime"
: {
"ts"
: Timestamp(0, 0),
"t"
: NumberLong(-1)
},
"optimeDate"
: ISODate(
"1970-01-01T00:00:00Z"
),
"lastHeartbeat"
: ISODate(
"2017-11-23T02:01:17.316Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-23T02:01:04.327Z"
),
"pingMs"
: NumberLong(0),
"lastHeartbeatMessage"
:
"Connection refused"
,
"configVersion"
: -1
},
{
"_id"
: 1,
"name"
:
"sign-mongo02.wangshibo.cn:27018"
,
"health"
: 1,
"state"
: 1,
"stateStr"
:
"PRIMARY"
,
"uptime"
: 44080,
"optime"
: {
"ts"
: Timestamp(1511402475, 2),
"t"
: NumberLong(4)
},
"optimeDate"
: ISODate(
"2017-11-23T02:01:15Z"
),
"infoMessage"
:
"could not find member to sync from"
,
"electionTime"
: Timestamp(1511402475, 1),
"electionDate"
: ISODate(
"2017-11-23T02:01:15Z"
),
"configVersion"
: 5,
"self"
:
true
},
{
"_id"
: 3,
"name"
:
"sign-mongo03.wangshibo.cn:27019"
,
"health"
: 1,
"state"
: 7,
"stateStr"
:
"ARBITER"
,
"uptime"
: 145,
"lastHeartbeat"
: ISODate(
"2017-11-23T02:01:17.315Z"
),
"lastHeartbeatRecv"
: ISODate(
"2017-11-23T02:01:15.316Z"
),
"pingMs"
: NumberLong(0),
"configVersion"
: 5
}
],
"ok"
: 1
}
rs0:PRIMARY> show dbs
local
0.000GB
mydb 0.000GB
有上面信息可知，添加仲裁节点后，primary能正常启动切换了！~
现在看看arbiter，连接到172.16.51.218:27019
[app@sign-mongo03 ~]$ mongo 172.16.51.218:27019
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.218:27019
/test
Welcome to the MongoDB shell.
For interactive help,
type
"help"
.
For
more
comprehensive documentation, see
http:
//docs
.mongodb.org/
Questions? Try the support group
http:
//groups
.google.com
/group/mongodb-user
Server has startup warnings:
2017-11-23T09:58:34.978+0800 I CONTROL [initandlisten]
2017-11-23T09:58:34.978+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/enabled
is
'always'
.
2017-11-23T09:58:34.978+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-23T09:58:34.978+0800 I CONTROL [initandlisten]
2017-11-23T09:58:34.978+0800 I CONTROL [initandlisten] ** WARNING:
/sys/kernel/mm/transparent_hugepage/defrag
is
'always'
.
2017-11-23T09:58:34.978+0800 I CONTROL [initandlisten] ** We suggest setting it to
'never'
2017-11-23T09:58:34.978+0800 I CONTROL [initandlisten]
rs0:ARBITER> rs.slaveOk();
rs0:ARBITER> db.isMaster()
{
"hosts"
: [
"sign-mongo01.wangshibo.cn:27017"
,
"sign-mongo02.wangshibo.cn:27018"
],
"arbiters"
: [
"sign-mongo03.wangshibo.cn:27019"
],
"setName"
:
"rs0"
,
"setVersion"
: 5,
"ismaster"
:
false
,
"secondary"
:
false
,
"primary"
:
"sign-mongo02.wangshibo.cn:27018"
,
"arbiterOnly"
:
true
,
"me"
:
"sign-mongo03.wangshibo.cn:27019"
,
"maxBsonObjectSize"
: 16777216,
"maxMessageSizeBytes"
: 48000000,
"maxWriteBatchSize"
: 1000,
"localTime"
: ISODate(
"2017-11-23T02:03:33.874Z"
),
"maxWireVersion"
: 4,
"minWireVersion"
: 0,
"ok"
: 1
}
rs0:ARBITER> show dbs
local
0.000GB
arbiter 最为仲裁者，没有数据副本存储在本地，能读取复制集的信息。
-------------------------------------------------------------------------------------------------
在primary主库上，创建locs数据库，该库的用户名为locsopr，密码为locsopr@123
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
......
rs0:PRIMARY> use locs
switched to db locs
rs0:PRIMARY> db.createUser({user:
"locsopr"
,
pwd
:
"locsopr@123"
,roles:[
"readWrite"
]})
Successfully added user: {
"user"
:
"locsopr"
,
"roles"
: [
"readWrite"
] }
rs0:PRIMARY> show
users
;
//
查看当前库下的用户名
{
"_id"
:
"locs.locsopr"
,
"user"
:
"locsopr"
,
"db"
:
"locs"
,
"roles"
: [
{
"role"
:
"readWrite"
,
"db"
:
"locs"
}
]
}
使用上面的用户登录primary主库
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
/locs
-ulocsopr -plocsopr@123
.........
rs0:PRIMARY> show
users
{
"_id"
:
"locs.locsopr"
,
"user"
:
"locsopr"
,
"db"
:
"locs"
,
"roles"
: [
{
"role"
:
"readWrite"
,
"db"
:
"locs"
}
]
}
rs0:PRIMARY> show dbs
admin 0.000GB
local
0.000GB
rs0:PRIMARY>
再登录从库看下：
[app@sign-mongo01 ~]$ mongo 172.16.51.216:27017
/locs
-ulocsopr -plocsopr@123
.......
rs0:SECONDARY> rs.slaveOk();
rs0:SECONDARY> show
users
{
"_id"
:
"locs.locsopr"
,
"user"
:
"locsopr"
,
"db"
:
"locs"
,
"roles"
: [
{
"role"
:
"readWrite"
,
"db"
:
"locs"
}
]
}
rs0:SECONDARY> show dbs
admin 0.000GB
local
0.000GB
|
-------------------------------------------------------------------------------------------------------------------------------------------------------
上面介绍的是三台mongodb节点：一主一备一仲裁，这样，主节点挂了后，通过仲裁机制将primary自动切换到备机上！
如果上面的三台mongodb节点：一主两备，没有仲裁节点，那么主节点挂了后，primary会自动切换到其余两台备节点中的一台上！
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一主两从（端口分别为27017、27018、27019）的mongodb配置和上面一主一从（端口分别为27017、27018）的配置一样。
多加的一个从节点，在主节点登陆mongodb，使用rs.add命令将这个成员加到集群中即可！
一主两从的模式，比如：
主节点sign-mongo01.wangshibo.cn的mongodb服务程序挂了后，另外两个从节点中的一个（比如sign-mongo02.wangshibo.cn）会自动变成primary主节点，
另一个节点sign-mongo03.wangshibo.cn则是新的主节点（sign-mongo02.wangshibo.cn）的从节点。
++++++++++++++++++++++++++++++如果想让切换回原来的主节点，做法如下+++++++++++++++++++++++++++++++
1）恢复原来的主节点sign-mongo01.wangshibo.cn的mongodb服务，使用命令rs.status() 确认数据集成员运行正常。
2）到次节点sign-mongo03.wangshibo.cn中登录mongodb，运行freeze使其120内不会变为主节点。
> rs.freeze(120)
3) 到新的主节点sign-mongo02.wangshibo.cn中强制切换主节点，stepDown将阻止长事务和写入操作
> rs.stepDown(120)
4）此时sign-mongo01.wangshibo.cn节点变成primary主节点。使用rs.status()命令可以查看到集群状态。
+++++++++++++++++++++++若要使某个节点永远不会变为主节点，设置优先级为0即可+++++++++++++++++++++++
登陆当前主节点的mongodb，执行下面操作：
rs0:PRIMARY> cfg = rs.conf()
rs0:PRIMARY> cfg.members[0].priority = 0.5
rs0:PRIMARY> cfg.members[1].priority = 0.5
rs0:PRIMARY> cfg.members[2].priority = 0
rs0:PRIMARY> rs.reconfig(cfg)
说明：
其中成员编号0
/1/2
为 rs.status()中的
"_id"
值
members[2]表示sign-mongo03.wangshibo.cn，则它将永远不会变成主节点！因为优先级设置为0了！
++++++++++++++++++++++++++++++++移除一个复制成员（两种方法）++++++++++++++++++++++++++++++++++++
登陆当前主节点的mongodb，执行下面操作：
rs0:PRIMARY> rs.remove(
"sign-mongo03.wangshibo.cn:27019"
)
rs0:PRIMARY> rs.conf()
或者：
rs0:PRIMARY> cfg = rs.conf()
rs0:PRIMARY> cfg.members.splice(2,1)
rs0:PRIMARY> rs.reconfig(cfg)
移除后到移除的节点服务器（即sign-mongo03.wangshibo.cn），更改配置文件mongod.conf
#replSet=rs0 //将这一行注释
然后再重启mongodb服务，这就完成了移除（数据库文件仍保留在当前服务器）。
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本文转自散尽浮华博客园博客，原文链接：http://www.cnblogs.com/kevingrace/p/7881496.html，如需转载请自行联系原作者
