1、MongoDB 主从复制
MongoDB复制是将数据同步在多个服务器的过程。
复制提供了数据的冗余备份，并在多个服务器上存储数据副本，提高了数据的可用性， 并可以保证数据的安全性。
复制还允许您从硬件故障和服务中断中恢复数据。
官方文档 https://docs.mongodb.com/manual/replication/
1.1 什么是复制?
保障数据的安全性 数据高可用性 (24*7) 灾难恢复 无需停机维护（如备份，重建索引，压缩） 分布式读取数据
1.2 MongoDB复制原理
mongodb的复制至少需要两个节点。其中一个是主节点，负责处理客户端请求，其余的都是从节点，负责复制主节点上的数据。
mongodb各个节点常见的搭配方式为：一主一从、一主多从。
主节点记录在其上的所有操作oplog，从节点定期轮询主节点获取这些操作，然后对自己的数据副本执行这些操作，从而保证从节点的数据与主节点一致。
MongoDB复制结构图如下所示：
以上结构图中，客户端从主节点读取数据，在客户端写入数据到主节点时， 主节点与从节点进行数据交互保障数据的一致性。
1.3 副本集特征
N 个节点的集群 任何节点可作为主节点 所有写入操作都在主节点上 自动故障转移 自动恢复
1.4 MongoDB副本集设置
1、关闭正在运行的MongoDB服务器。
service mongod stop 2.节点建点
首先需要去你选择的mongodb数据文件存放的文件夹新建三个数据库，用来模拟三台不通的机器，博主的路径如下
mkdir -p /data/db/node1 mkdir -p /data/db/node2 mkdir -p /data/db/node3 3.启动三个数据库（dbpath），并且端口（－－port 1000x），集群名称（－－replSet gabriel），关闭日志选项（－－nojournal），守护进程方式启动,会自动拉起（－－fork），日志目录（－－logpath）
mongod --dbpath /data/db/node1 --port 10001 --replSet gabriel --nojournal --fork --logpath /data/db/node1.log mongod --dbpath /data/db/node2 --port 10002 --replSet gabriel --nojournal --fork --logpath /data/db/node2.log mongod --dbpath /data/db/node3 --port 10003 --replSet gabriel --nojournal --fork --logpath /data/db/node3.log 4.顺便连接一个服务器，做初始化操作，这里博主连入10001端口
终端下进入
mongo localhost:10001 进入后输入初始化方法
MongoDB Enterprise gabriel:OTHER> rs.initiate({_id:"gabriel",members:[ {_id:1,host:"localhost:10001"}, {_id:2,host:"localhost:10002"}, {_id:3,host:"localhost:10003"}, ]}) 收到如下信息就成功了。
{
"ok" : 1, "operationTime" : Timestamp(1517221411, 1), "$clusterTime" : { "clusterTime" : Timestamp(1517221411, 1), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } } } MongoDB Enterprise gabriel:OTHER> 此时会发现终端上的输出已经有了变化。
//从单个一个 > //变成了 gabriel:OTHER> 5.查询状态
MongoDB Enterprise gabriel:OTHER> rs.status() { "set" : "gabriel", "date" : ISODate("2018-01-29T10:33:21.227Z"), "myState" : 1, "term" : NumberLong(1), "heartbeatIntervalMillis" : NumberLong(2000), "optimes" : { "lastCommittedOpTime" : { "ts" : Timestamp(1517221984, 1), "t" : NumberLong(1) }, "readConcernMajorityOpTime" : { "ts" : Timestamp(1517221984, 1), "t" : NumberLong(1) }, "appliedOpTime" : { "ts" : Timestamp(1517221994, 1), "t" : NumberLong(1) }, "durableOpTime" : { "ts" : Timestamp(1517221994, 1), "t" : NumberLong(1) } }, "members" : [ { "_id" : 1, "name" : "localhost:10001", "health" : 1, "state" : 1, "stateStr" : "PRIMARY", "uptime" : 659, "optime" : { "ts" : Timestamp(1517221994, 1), "t" : NumberLong(1) }, "optimeDate" : ISODate("2018-01-29T10:33:14Z"), "electionTime" : Timestamp(1517221422, 1), "electionDate" : ISODate("2018-01-29T10:23:42Z"), "configVersion" : 1, "self" : true }, { "_id" : 2, "name" : "localhost:10002", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 589, "optime" : { "ts" : Timestamp(1517221994, 1), "t" : NumberLong(1) }, "optimeDurable" : { "ts" : Timestamp(1517221984, 1), "t" : NumberLong(1) }, "optimeDate" : ISODate("2018-01-29T10:33:14Z"), "optimeDurableDate" : ISODate("2018-01-29T10:33:04Z"), "lastHeartbeat" : ISODate("2018-01-29T10:33:20.972Z"), "lastHeartbeatRecv" : ISODate("2018-01-29T10:33:19.923Z"), "pingMs" : NumberLong(0), "syncingTo" : "localhost:10001", "configVersion" : 1 }, { "_id" : 3, "name" : "localhost:10003", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 589, "optime" : { "ts" : Timestamp(1517221994, 1), "t" : NumberLong(1) }, "optimeDurable" : { "ts" : Timestamp(1517221984, 1), "t" : NumberLong(1) }, "optimeDate" : ISODate("2018-01-29T10:33:14Z"), "optimeDurableDate" : ISODate("2018-01-29T10:33:04Z"), "lastHeartbeat" : ISODate("2018-01-29T10:33:20.972Z"), "lastHeartbeatRecv" : ISODate("2018-01-29T10:33:19.921Z"), "pingMs" : NumberLong(0), "syncingTo" : "localhost:10001", "configVersion" : 1 } ], "ok" : 1, "operationTime" : Timestamp(1517221994, 1), "$clusterTime" : { "clusterTime" : Timestamp(1517221994, 1), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } } } 在返回中，参数set后面为集群名称，每个members下面可以看到他们各自的情况，其中stateStr是角色，主节点为（PRIMARY）。
6.进入主节点插入数据，进入从节点查看数据
博主主节点在10001接口
mongo localhost:10001 插入数据
MongoDB Enterprise gabriel:PRIMARY> use test switched to db test db.col.insert({title: 'MongoDB 教程', description: 'MongoDB 是一个 Nosql 数据库', by: '小罗技术笔记-专注于开发技术的研究与知识分享', url: 'http://www.yuwowugua.com', tags: ['mongodb', 'database', 'NoSQL'], likes: 100 }) MongoDB Enterprise gabriel:PRIMARY> db.col.find() { "_id" : ObjectId("5a6ef998525d903d07a00cdf"), "title" : "MongoDB 教程", "description" : "MongoDB 是一个 Nosql 数据库", "by" : "小罗技术笔记-专注于开发技术的研究与知识分享", "url" : "http://www.yuwowugua.com", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 100 } MongoDB Enterprise gabriel:PRIMARY> 博主切换从节点10002
mongo localhost:10002 切换到从节点，你会发现使用show dbs 会报错，是因为还没有开启权限，输入rs.slaveOk();就可以顺利访问了。
MongoDB Enterprise gabriel:SECONDARY> show dbs
2018-01-29T10:40:37.362+0000 E QUERY [thread1] Error: listDatabases failed:{ "operationTime" : Timestamp(1517222434, 1), "ok" : 0, "errmsg" : "not master and slaveOk=false", "code" : 13435, "codeName" : "NotMasterNoSlaveOk", "$clusterTime" : { "clusterTime" : Timestamp(1517222434, 1), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } } } : _getErrorWithCode@src/mongo/shell/utils.js:25:13 Mongo.prototype.getDBs@src/mongo/shell/mongo.js:65:1 shellHelper.show@src/mongo/shell/utils.js:813:19 shellHelper@src/mongo/shell/utils.js:703:15 @(shellhelp2):1:1 MongoDB Enterprise gabriel:SECONDARY> MongoDB Enterprise gabriel:SECONDARY> rs.slaveOk() 再次查看
MongoDB Enterprise gabriel:SECONDARY> show dbs admin 0.000GB config 0.000GB local 0.000GB test 0.000GB MongoDB Enterprise gabriel:SECONDARY> 切到test 库，查看数据已经同步过来了
MongoDB Enterprise gabriel:SECONDARY> use test switched to db test MongoDB Enterprise gabriel:SECONDARY> db.col.find() { "_id" : ObjectId("5a6ef998525d903d07a00cdf"), "title" : "MongoDB 教程", "description" : "MongoDB 是一个 Nosql 数据库", "by" : "小罗技术笔记-专注于开发技术的研究与知识分享", "url" : "http://www.yowowugua.com", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 100 } MongoDB Enterprise gabriel:SECONDARY> 以上就是简单的主从复制建立过程，现在已经可以在从服务器看到主服务器插入的数据了。
切换从节点10003 一样的问题
删除从节点
rs.remove('ip:port') 关闭主服务器后，再重新启动，会发现原来的从服务器变为了从服务器，新启动的服务器（原来的从服务器）变为了从服务器
2、 MongoDB 自动故障转移
首先通过 rs.status() 查看，可以看到主节点是10001，主节点"name" :
"localhost:10001", "stateStr" : "PRIMARY" 接下来停止 10001 主节点，测试故障切换
MongoDB Enterprise gabriel:PRIMARY> rs.status() { "set" : "gabriel", "date" : ISODate("2018-01-30T02:39:58.468Z"), "myState" : 1, "term" : NumberLong(1), "heartbeatIntervalMillis" : NumberLong(2000), "optimes" : { "lastCommittedOpTime" : { "ts" : Timestamp(1517279986, 1), "t" : NumberLong(1) }, "readConcernMajorityOpTime" : { "ts" : Timestamp(1517279986, 1), "t" : NumberLong(1) }, "appliedOpTime" : { "ts" : Timestamp(1517279996, 1), "t" : NumberLong(1) }, "durableOpTime" : { "ts" : Timestamp(1517279996, 1), "t" : NumberLong(1) } }, "members" : [ { "_id" : 1, "name" : "localhost:10001", "health" : 1, "state" : 1, "stateStr" : "PRIMARY", "uptime" : 58656, "optime" : { "ts" : Timestamp(1517279996, 1), "t" : NumberLong(1) }, "optimeDate" : ISODate("2018-01-30T02:39:56Z"), "electionTime" : Timestamp(1517221422, 1), "electionDate" : ISODate("2018-01-29T10:23:42Z"), "configVersion" : 1, "self" : true }, { "_id" : 2, "name" : "localhost:10002", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 58586, "optime" : { "ts" : Timestamp(1517279996, 1), "t" : NumberLong(1) }, "optimeDurable" : { "ts" : Timestamp(1517279986, 1), "t" : NumberLong(1) }, "optimeDate" : ISODate("2018-01-30T02:39:56Z"), "optimeDurableDate" : ISODate("2018-01-30T02:39:46Z"), "lastHeartbeat" : ISODate("2018-01-30T02:39:58.289Z"), "lastHeartbeatRecv" : ISODate("2018-01-30T02:39:57.220Z"), "pingMs" : NumberLong(0), "syncingTo" : "localhost:10001", "configVersion" : 1 }, { "_id" : 3, "name" : "localhost:10003", "health" : 0, "state" : 8, "stateStr" : "(not reachable/healthy)", "uptime" : 0, "optime" : { "ts" : Timestamp(0, 0), "t" : NumberLong(-1) }, "optimeDurable" : { "ts" : Timestamp(0, 0), "t" : NumberLong(-1) }, "optimeDate" : ISODate("1970-01-01T00:00:00Z"), "optimeDurableDate" : ISODate("1970-01-01T00:00:00Z"), "lastHeartbeat" : ISODate("2018-01-30T02:39:58.304Z"), "lastHeartbeatRecv" : ISODate("2018-01-30T02:39:21.208Z"), "pingMs" : NumberLong(0), "lastHeartbeatMessage" : "Connection refused", "configVersion" : -1 } ], "ok" : 1, "operationTime" : Timestamp(1517279996, 1), "$clusterTime" : { "clusterTime" : Timestamp(1517279996, 1), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } } } MongoDB Enterprise gabriel:PRIMARY> 连接到主节点
mongo localhost:10001 显示所有数据库
MongoDB Enterprise gabriel:PRIMARY> show dbs admin 0.000GB config 0.000GB local 0.000GB test 0.000GB 切换到admin
MongoDB Enterprise gabriel:PRIMARY> use admin switched to db admin 停止数据库，必须进入 admin 库
MongoDB Enterprise gabriel:PRIMARY> db.shutdownServer() 响应
2018-01-30T02:51:34.503+0000 I NETWORK [thread1] trying reconnect to localhost:10001 (127.0.0.1) failed 2018-01-30T02:51:35.398+0000 I NETWORK [thread1] Socket recv() Connection reset by peer 127.0.0.1:10001 2018-01-30T02:51:35.398+0000 I NETWORK [thread1] SocketException: remote: (NONE):0 error: SocketException socket exception [RECV_ERROR] server [127.0.0.1:10001] 2018-01-30T02:51:35.399+0000 I NETWORK [thread1] reconnect localhost:10001 (127.0.0.1) failed failed 2018-01-30T02:51:35.404+0000 I NETWORK [thread1] trying reconnect to localhost:10001 (127.0.0.1) failed 2018-01-30T02:51:35.404+0000 W NETWORK [thread1] Failed to connect to 127.0.0.1:10001, in(checking socket for error after poll), reason: Connection refused 2018-01-30T02:51:35.404+0000 I NETWORK [thread1] reconnect localhost:10001 (127.0.0.1) failed failed MongoDB Enterprise > 查看是否真的停止了,发现已经没有10001 节点进程了
root@admin-2:# ps -ef | grep mongo root 5554 1 0 Jan29 ? 00:03:34 mongod --dbpath /data/db/node2 --port 10002 --replSet gabriel --nojournal --fork --logpath /data/db/node2.log root 12284 1 0 02:43 ? 00:00:02 mongod --dbpath /data/db/node3 --port 10003 --replSet gabriel --nojournal --fork --logpath /data/db/node3.log root 12436 5132 0 02:53 pts/1 00:00:00 grep --color=auto mongo root@admin-2:# netstat -nltp Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:10002 0.0.0.0:* LISTEN 5554/mongod tcp 0 0 127.0.0.1:10003 0.0.0.0:* LISTEN 12284/mongod root@admin-2:/data/db# 查看是否故障专业
root@admin-2:# mongo localhost:10001 查看主从状态
MongoDB Enterprise gabriel:SECONDARY> rs.status() { "set" : "gabriel", "date" : ISODate("2018-01-30T02:56:48.074Z"), "myState" : 2, "term" : NumberLong(2), "syncingTo" : "localhost:10003", "heartbeatIntervalMillis" : NumberLong(2000), "optimes" : { "lastCommittedOpTime" : { "ts" : Timestamp(1517280995, 1), "t" : NumberLong(2) }, "readConcernMajorityOpTime" : { "ts" : Timestamp(1517280995, 1), "t" : NumberLong(2) }, "appliedOpTime" : { "ts" : Timestamp(1517281005, 1), "t" : NumberLong(2) }, "durableOpTime" : { "ts" : Timestamp(1517280995, 1), "t" : NumberLong(2) } }, "members" : [ { "_id" : 1, "name" : "localhost:10001", "health" : 0, "state" : 8, "stateStr" : "(not reachable/healthy)", "uptime" : 0, "optime" : { "ts" : Timestamp(0, 0), "t" : NumberLong(-1) }, "optimeDurable" : { "ts" : Timestamp(0, 0), "t" : NumberLong(-1) }, "optimeDate" : ISODate("1970-01-01T00:00:00Z"), "optimeDurableDate" : ISODate("1970-01-01T00:00:00Z"), "lastHeartbeat" : ISODate("2018-01-30T02:56:47.605Z"), "lastHeartbeatRecv" : ISODate("2018-01-30T02:51:34.519Z"), "pingMs" : NumberLong(0), "lastHeartbeatMessage" : "Connection refused", "configVersion" : -1 }, { "_id" : 2, "name" : "localhost:10002", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 59660, "optime" : { "ts" : Timestamp(1517281005, 1), "t" : NumberLong(2) }, "optimeDate" : ISODate("2018-01-30T02:56:45Z"), "syncingTo" : "localhost:10003", "configVersion" : 1, "self" : true }, { "_id" : 3, "name" : "localhost:10003", "health" : 1, "state" : 1, "stateStr" : "PRIMARY", "uptime" : 784, "optime" : { "ts" : Timestamp(1517281005, 1), "t" : NumberLong(2) }, "optimeDurable" : { "ts" : Timestamp(1517281005, 1), "t" : NumberLong(2) }, "optimeDate" : ISODate("2018-01-30T02:56:45Z"), "optimeDurableDate" : ISODate("2018-01-30T02:56:45Z"), "lastHeartbeat" : ISODate("2018-01-30T02:56:46.486Z"), "lastHeartbeatRecv" : ISODate("2018-01-30T02:56:47.147Z"), "pingMs" : NumberLong(0), "electionTime" : Timestamp(1517280703, 1), "electionDate" : ISODate("2018-01-30T02:51:43Z"), "configVersion" : 1 } ], "ok" : 1, "operationTime" : Timestamp(1517281005, 1), "$clusterTime" : { "clusterTime" : Timestamp(1517281005, 1), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } } } MongoDB Enterprise gabriel:SECONDARY> 发现 “name” : “localhost:10001”,”stateStr” : “(not reachable/healthy)”, 健康状态已经是“无法访问状态了”
主节点已经切换成 10003 节点了
"_id" : 3, "name" : "localhost:10003", "health" : 1, "state" : 1, "stateStr" : "PRIMARY", 重启节点10001
mongod --dbpath /data/db/node1 --port 10001 --replSet gabriel --nojournal --fork --logpath /data/db/node1.log
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