Deploying the config server replica set

The next step is to deploy the config server. As mentioned earlier in this chapter, the config server stores sharding metadata and must be deployed as a replica set.

Accordingly, the mongod.conf file appears as follows:

systemLog:
   destination: file
   path: "/var/log/mongodb/mongodb.log"
   logAppend: true
storage:
   dbPath: "/data/db"
   journal:
      enabled: true
net:
   bindIp: 0.0.0.0
   port: 27019
replication:
   replSetName: repl_config
sharding:
   clusterRole: configsvr

To initialize the replica set, we use the rs.initiate() shell method. The following syntax is sufficient for the purposes of this illustration:

doc = {
    _id : "repl_config",
    members: [
        { _id: 1, host: "config1.biglittle.local:27019" }
    ]
}
rs.initiate(doc);

We open a mongo shell on the config server and issue the command shown in the preceding code block. As discussed earlier in this section, we initiate a single-node replica set...