MongoDB Replica Set replica set
1. Introduction
MongoDB replication is the process of synchronizing data on multiple servers, similar to MySQL Replication, which is an asynchronous replication
Replication provides redundant backup of data, and stores copies of data on multiple servers, which improves the availability of data and ensures the security of data.
2. Characteristics of MongoDB replication
(1) the node of mongodb has three roles: primary,seconfary,arbiter
Primary is responsible for processing client requests, reading and writing data
Secondary replicates the data on the primary node through oplog and can also read the data
Arbiter nodes do not store data and only vote, so no separate hardware configuration is required
(2) if primary is not available, secondary will be promoted to the new primary; controlled by the parameter electionTimeoutMillis=10s.
3. Experimental environment
MongoDB-3.0.6 version
Three MongoDB instances on one physical machine, each occupying three nodes
172.16.101.54 27017
172.16.101.54 27018
172.16.101.54 27019
4. Create data and log directories
[root@sht-sgmhadoopcm-01 mongodb] # mkdir-p / usr/local/mongodb/data/ {db27017,db27018,db27019}
[root@sht-sgmhadoopcm-01 mongodb] # mkdir-p / usr/local/mongodb/log
5. Configuration file / etc/mongod.conf
The three nodes create configuration files respectively. The difference in the content of the file is that the nodes are different, but the others are all the same. The parameter replSetname is used to specify that the replica set name is rs0.
[root@sht-sgmhadoopcm-01 mongodb] # ll / etc/mongod2701*.conf
-rw-r--r-- 1 root root 405 Nov 2 20:21 / etc/mongod27017.conf
-rw-r--r-- 1 root root 405 Nov 2 20:13 / etc/mongod27018.conf
-rw-r--r-- 1 root root 405 Nov 2 20:13 / etc/mongod27019.conf
Mongodb configuration files should be followed by a space after each colon, otherwise an error will be reported
[root@sht-sgmhadoopcm-01 mongodb] # cat / etc/mongod27017.confsystemLog: destination: file path: "/ usr/local/mongodb/log/mongod27017.log" logAppend: dbPath: / usr/local/mongodb/data/db27017 journal: enabled: trueprocessManagement: fork: true pidFilePath: / usr/local/mongodb/data/db27017/mongod27017.pidnet: port: 27017 bindIp: 0.0.0.0setParameter: enableLocalhostAuthBypass: falsereplication: replSetName: rs0
6. Start MongoDB
Start the MongoDB service for each of the three nodes and specify the configuration file
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongod-- config / etc/mongod27017.conf
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongod-- config / etc/mongod27018.conf
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongod-- config / etc/mongod27019.conf
7. Initialize the replica set
Log in to the 27017 node
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongo 172.16.101.54:27017/admin
> rs.initiate ()
{
"info2": "no configuration explicitly specified-making one"
"me": "sht-sgmhadoopcm-01:27017"
"ok": 1
}
If you add a member to the replica set, the node with large priority is more likely to receive a commission.
Rs0:PRIMARY > rs.add ('172.16.101.54 virtual 27018')
{"ok": 1}
Rs0:PRIMARY > rs.add ('172.16.101.54) 27019 priority5)
{"ok": 1}
View replica set configuration
Rs0:PRIMARY > rs.conf () {"_ id": "rs0", "version": 3, "members": [{"_ id": 0, "host": "sht-sgmhadoopcm-01:27017", "arbiterOnly": false, "buildIndexes": true, "hidden": false "priority": 1, "tags": {}, "slaveDelay": 0, "votes": 1}, {"_ id": 1, "host": "172.16.101.54 slaveDelay 27018", "arbiterOnly": false "buildIndexes": true, "hidden": false, "priority": 1, "tags": {}, "slaveDelay": 0, "votes": 1}, {"_ id": 2 "host": "172.16.101.54 true", "arbiterOnly": false, "buildIndexes": true, "hidden": false, "priority": 1, "tags": {}, "slaveDelay": 0 "votes": 1}], "settings": {"chainingAllowed": true, "heartbeatTimeoutSecs": 10, "getLastErrorModes": {}, "getLastErrorDefaults": {"w": 1, "wtimeout": 0}
View the status of each role
Rs0:PRIMARY > rs.status () {"set": "rs0", "date": ISODate ("2018-11-02T12:27:44.570Z"), "myState": 1, "members": [{"_ id": 0, "name": "sht-sgmhadoopcm-01:27017", "health": 1, "state": 1 "stateStr": "PRIMARY", "uptime": 626, "optime": Timestamp (1541161589, 1), "optimeDate": ISODate ("2018-11-02T12:26:29Z"), "electionTime": Timestamp (1541161465, 2), "electionDate": ISODate ("2018-11-02T12:24:25Z"), "configVersion": 3 "self": true}, {"_ id": 1, "name": "172.16.101.54 name", "health": 1, "state": 2, "stateStr": "SECONDARY", "uptime": 161, "optime": Timestamp (1541161589 1), "optimeDate": ISODate ("2018-11-02T12:26:29Z"), "lastHeartbeat": ISODate ("2018-11-02T12:27:43.430Z"), "lastHeartbeatRecv": ISODate ("2018-11-02T12:27:43.311Z"), "pingMs": 0, "syncingTo": "sht-sgmhadoopcm-01:27017" "configVersion": 3}, {"_ id": 2, "name": "172.16.101.54 health", "health": 1, "state": 2, "stateStr": "SECONDARY", "uptime": 75, "optime": Timestamp (1541161589) 1), "optimeDate": ISODate ("2018-11-02T12:26:29Z"), "lastHeartbeat": ISODate ("2018-11-02T12:27:43.430Z"), "lastHeartbeatRecv": ISODate ("2018-11-02T12:27:43.430Z"), "pingMs": 0, "lastHeartbeatMessage": "could not find member to sync from" "configVersion": 3}], "ok": 1}
8. Data synchronization test
Insert data into 27017 nodes
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongo 172.16.101.54:27017/admin
Rs0:PRIMARY > db.user.insert ({"username": "test", "age": 12, "sex": "m"})
WriteResult ({"nInserted": 1})
Rs0:PRIMARY > db.user.find ()
{"_ id": ObjectId ("5bdc65ff048de313da6c425a"), "username": "test", "age": 12, "sex": "m"}
Data successfully synchronized to 27018 and 27019 nodes
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongo 172.16.101.54:27018/admin
Rs0:SECONDARY > db.getMongo (). SetReadPref ('secondaryPreferred')
Rs0:SECONDARY > db.user.find ()
{"_ id": ObjectId ("5bdc65ff048de313da6c425a"), "username": "test", "age": 12, "sex": "m"}
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongo 172.16.101.54:27019/admin
Rs0:SECONDARY > db.getMongo (). SetReadPref ('secondaryPreferred')
Rs0:SECONDARY > db.user.find ()
{"_ id": ObjectId ("5bdc65ff048de313da6c425a"), "username": "test", "age": 12, "sex": "m"}
9. AutoFailover test
Kill's current primary27017 node
[root@sht-sgmhadoopcm-01 mongodb] # ps-ef | grep mongod
Root 5703 1 0 20:17? 00:00:52 bin/mongod-- config / etc/mongod27017.conf
Root 5747 1 0 20:17? 00:00:51 bin/mongod-- config / etc/mongod27018.conf
Root 5979 1 0 20:20? 00:00:52 bin/mongod-- config / etc/mongod27019.conf
[root@sht-sgmhadoopcm-01 mongodb] # kill-9 5703
You can see that 27019 becomes primary and 27017 is not available at this time
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongo 172.16.101.54:27018/admin
Rs0:SECONDARY > rs.status () {"set": "rs0", "date": ISODate ("2018-11-02T15:10:18.746Z"), "myState": 2, "members": [{"_ id": 0, "name": "sht-sgmhadoopcm-01:27017", "health": 0, "state": 8 "stateStr": (not reachable/healthy), "uptime": 0, "optime": Timestamp (0,0), "optimeDate": ISODate ("1970-01-01T00:00:00Z"), "lastHeartbeat": ISODate ("2018-11-02T15:10:18.631Z") "lastHeartbeatRecv": ISODate ("2018-11-02T15:09:28.583Z"), "pingMs": 0, "lastHeartbeatMessage": "Failed attempt to connect to sht-sgmhadoopcm-01:27017 Couldn't connect to server sht-sgmhadoopcm-01:27017 (172.16.101.54), connection attempt failed "," configVersion ":-1}, {" _ id ": 1," name ":" 172.16.101.54 name "," health ": 1," state ": 2 "stateStr": "SECONDARY", "uptime": 10349, "optime": Timestamp (1541170688, 2), "optimeDate": ISODate ("2018-11-02T14:58:08Z"), "configVersion": 3, "self": true}, {"_ id": 2 "name": "172.16.101.54 PRIMARY", "health": 1, "state": 1, "stateStr": "PRIMARY", "uptime": 9827, "optime": Timestamp (1541170688, 2), "optimeDate": ISODate ("2018-11-02T14:58:08Z") LastHeartbeat: ISODate ("2018-11-02T15:10:18.611Z"), "lastHeartbeatRecv": ISODate ("2018-11-02T15:10:18.592Z"), "pingMs": 0, "electionTime": Timestamp (1541171370, 1), "electionDate": ISODate ("2018-11-02T15:09:30Z") "configVersion": 3}], "ok": 1}
If you restart the 27017 node, it will automatically become a 27019 standby library, indicating that auto failover is successful.
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongod-- config / etc/mongod27017.conf
Rs0:PRIMARY > rs.status () {"set": "rs0", "date": ISODate ("2018-11-02T15:13:27.035Z"), "myState": 1, "members": [{"_ id": 0, "name": "sht-sgmhadoopcm-01:27017", "health": 1, "state": 2 StateStr: "SECONDARY", "uptime": 42, "optime": Timestamp (1541170688, 2), "optimeDate": ISODate ("2018-11-02T14:58:08Z"), "lastHeartbeat": ISODate ("2018-11-02T15:13:26.764Z"), "lastHeartbeatRecv": ISODate ("2018-11-02T15:13:25.055Z") "pingMs": 0, "configVersion": 3}, {"_ id": 1, "name": "172.16.101.54 name", "health": 1, "state": 2, "stateStr": "SECONDARY", "uptime": 10017 Optime: Timestamp (1541170688, 2), optimeDate: ISODate ("2018-11-02T14:58:08Z"), "lastHeartbeat": ISODate ("2018-11-02T15:13:26.662Z"), "lastHeartbeatRecv": ISODate ("2018-11-02T15:13:26.678Z"), "pingMs": 0 "lastHeartbeatMessage": "could not find member to sync from", "configVersion": 3}, {"_ id": 2, "name": "172.16.101.54 id 27019", "health": 1, "state": 1, "stateStr": "PRIMARY" "uptime": 10349, "optime": Timestamp (1541170688, 2), "optimeDate": ISODate ("2018-11-02T14:58:08Z"), "electionTime": Timestamp (1541171370, 1), "electionDate": ISODate ("1541171370-11-02T15:09:30Z"), "configVersion": 3 "self": true}], "ok": 1}
FAQ
[root@sht-sgmhadoopcm-01 mongodb] # bin/mongod-config / etc/mongod27017.conf &
[1] 4885
[root@sht-sgmhadoopcm-01 mongodb] # Error parsing YAML config file: yaml-cpp: error at line 8, column 11: illegal map value
Try 'bin/mongod-- help' for more information
[1] + Exit 2 bin/mongod-- config / etc/mongod27017.conf
The reason is that the configuration file / etc/mongod.conf colon is not followed by a space.
Reference link
MongoDB Replication
