Configure MongoDB sharding (cluster)

To build mongodb sharding architecture, you have to have minimum:

• 1 shard (replica set / single mongod instance)
• 1 config server (replica set / single mongod instance) to store shard metadata
• mongos server to route queries to shards

   

Configuring Config Server Replica set (CSRS)

Config server is mongod instance that store sharding metadata of cluster. Its configuration is mostly same as default mongod config. Main difference is:

...

sharding:
  clusterRole: "configsvr"

...

Then you have to add this line to all CSRS members.

   

Configuring Shard replica sets

To mark replica set as shard you have to add cluster role of shardsvr to sharding replica set members config file:

...

sharding:
  clusterRole: "shardsvr"

...

   

Configuring MongoS

Mongos is service that routes queries to specific shard or executes queries in every shard and merges them for client.

Mongos does not have to have storage nor replica set. But if we need more mongos, we can just create multiple clones.

Example mongos config file:

net:
   bindIp: 127.0.0.1
   port: 29000

sharding:
  configDB: "myshard:config/localhost:29010,localhost:29011,localhost:29012"

systemLog:
   destination: file
   path: "/var/lib/mongodb/mongos/mongos.log"
   logAppend: true

processManagement:
   fork: true

setParameter:
   enableLocalhostAuthBypass: false

We have to show path to CSRS in mongos configuration, to fetch metadata

   

Initializing sharding cluster

First you have to start all shard replica sets, and CSRS.

To start mongos process:

mongos -f mongos.conf

After mongos started, we connect to it:

mongo --host "localhost:29000"

And to add shard replica sets:

sh.addShard("shard-1-replica-set/localhost:28001")

sh.addShard("shard-2-replica-set/localhost:28011")