The replica set is created by initiating replication on the replica set member server where the administrative user was created, and then adding the other replica set member servers to the set.
Connect with the mongo shell
On the replica set member where the mongoadmin user was created in the previous section (casdev-srv01 in our case), start the mongo shell again by running the command
casdev-srv01# mongo -u mongoadmin -p --authenticationDatabase admin
MongoDB shell version v3.6.0
Enter password:
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.6.0
>
and entering the correct password (“changeit”).
Initiate the replica set
From the mongo shell, run the command
> rs.initiate()
{
"info2" : "no configuration specified. Using a default configuration for the set",
"me" : "casdev-srv01.newschool.edu:27017",
"ok" : 1,
"operationTime" : Timestamp(1512664653, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1512664653, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}
>
Add members to the replica set
Continuing in the mongo shell, add the other members of the replica set:
> rs.add("casdev-srv02.newschool.edu")
{
"ok" : 1,
"operationTime" : Timestamp(1512664727, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1512664727, 1),
"signature" : {
"hash" : BinData(0,"wbhbHdhI1gtR+SWQSh2XARQw9jw="),
"keyId" : NumberLong("6496845223040122881")
}
}
}
> rs.add("casdev-srv03.newschool.edu")
{
"ok" : 1,
"operationTime" : Timestamp(1512664876, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1512664876, 1),
"signature" : {
"hash" : BinData(0,"gIrttrr3VzqhM2iIWxX5ITwMIhI="),
"keyId" : NumberLong("6496845223040122881")
}
}
}
>
Display the replica set configuration
To view the configuration of the replica set, use the rs.conf() command to the mongo shell:
> rs.conf()
{
"_id" : "rs0",
"version" : 3,
"protocolVersion" : NumberLong(1),
"members" : [
{
"_id" : 0,
"host" : "casdev-srv01.newschool.edu:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 1,
"host" : "casdev-srv02.newschool.edu:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 2,
"host" : "casdev-srv03.newschool.edu:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
}
],
"settings" : {
"chainingAllowed" : true,
"heartbeatIntervalMillis" : 2000,
"heartbeatTimeoutSecs" : 10,
"electionTimeoutMillis" : 10000,
"catchUpTimeoutMillis" : -1,
"catchUpTakeoverDelayMillis" : 30000,
"getLastErrorModes" : {
},
"getLastErrorDefaults" : {
"w" : 1,
"wtimeout" : 0
},
"replicaSetId" : ObjectId("5a296e4da9fdf50c1fc967ae")
}
}
>
Display the status of the replica set
To display dynamic information about the status of the replica set, use the rs.status() command instead:
> rs.status()
{
"set" : "rs0",
"date" : ISODate("YYYY-MM-DDTHH:MM:SS.sssZ"),
"myState" : 1,
"term" : NumberLong(1),
"heartbeatIntervalMillis" : NumberLong(2000),
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"readConcernMajorityOpTime" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"appliedOpTime" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"durableOpTime" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
}
},
"members" : [
{
"_id" : 0,
"name" : "casdev-srv01.newschool.edu:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 916,
"optime" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("YYYY-MM-DDTHH:MM:SSZ"),
"electionTime" : Timestamp(1512664653, 2),
"electionDate" : ISODate("2017-12-07T16:37:33Z"),
"configVersion" : 3,
"self" : true
},
{
"_id" : 1,
"name" : "casdev-srv02.newschool.edu:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 247,
"optime" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("YYYY-MM-DDTHH:MM:SSZ"),
"optimeDurableDate" : ISODate("YYYY-MM-DDTHH:MM:SSZ"),
"lastHeartbeat" : ISODate("YYYY-MM-DDTHH:MM:SS.sssZ"),
"lastHeartbeatRecv" : ISODate("YYYY-MM-DDTHH:MM:SS.sssZ"),
"pingMs" : NumberLong(0),
"syncingTo" : "casdev-srv01.newschool.edu:27017",
"configVersion" : 3
},
{
"_id" : 2,
"name" : "casdev-srv03.newschool.edu:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 99,
"optime" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1512664965, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("YYYY-MM-DDTHH:MM:SSZ"),
"optimeDurableDate" : ISODate("YYYY-MM-DDTHH:MM:SSZ"),
"lastHeartbeat" : ISODate("YYYY-MM-DDTHH:MM:SS.sssZ"),
"lastHeartbeatRecv" : ISODate("YYYY-MM-DDTHH:MM:SS.sssZ"),
"pingMs" : NumberLong(0),
"syncingTo" : "casdev-srv01.newschool.edu:27017",
"configVersion" : 3
}
],
"ok" : 1,
"operationTime" : Timestamp(1512664965, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1512664965, 1),
"signature" : {
"hash" : BinData(0,"wGZmpqOqx1Xz1XDrsa2129JAd+c="),
"keyId" : NumberLong("6496845223040122881")
}
}
}
>
The members[n].stateStr element indicates, for each member, whether it is the primary or a secondary member of the replica set.
Display current replication status
To display the current status of replicating data from the primary to the slave (secondary) servers, use the rs.printSlaveReplicationInfo() command:
> rs.printSlaveReplicationInfo()
source: casdev-srv02.newschool.edu:27017
syncedTo: Ddd MMM DD YYYY HH:MM:DD GMT-0500 (EST)
0 secs (0 hrs) behind the primary
source: casdev-srv03.newschool.edu:27017
syncedTo: Ddd MMM DD YYYY HH:MM:DD GMT-0500 (EST)
0 secs (0 hrs) behind the primary
>
Exit the mongo shell
Exit the mongo shell:
> exit
bye