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Sharding

sh.addShard()

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  • Definition
  • Compatibility
  • Considerations
  • Example

Definition

sh.addShard(<url>)

Adds a shard replica set to a sharded cluster. This method must be run on a mongos instance.

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for database commands or language-specific drivers, such as Node.js.

For the database command, see the addShard command.

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.

The sh.addShard() method has the following parameter:

Parameter
Type
Description
host
string

The replica set name, hostname, and port of at least one member of the shard's replica set. Any additional replica set member hostnames must be comma separated. For example:

<replica_set>/<hostname><:port>,<hostname><:port>, ...

The sh.addShard() method has the following prototype form:

sh.addShard("<replica_set>/<hostname><:port>")

Warning

Do not use localhost for the hostname unless your config server is also running on localhost.

mongos installed from official .deb and .rpm packages have the bind_ip configuration set to 127.0.0.1 by default.

mongos uses "majority" for the addShard command and its helper sh.addShard().

Compatibility

This method is available in deployments hosted in the following environments:

  • MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

Important

This command is not supported in serverless instances. For more information, see Unsupported Commands.

Considerations

Balancing

When you add a shard to a sharded cluster, you affect the balance of chunks among the shards of a cluster for all existing sharded collections. The balancer will begin migrating chunks so that the cluster will achieve balance. See Balancer Internals for more information.

Hidden Members

Important

You cannot include a hidden member in the seed list provided to sh.addShard().

DDL Operations

If you run sh.addShard while your cluster executes a DDL operation (operation that modifies a collection such as reshardCollection), sh.addShard only executes after the concurrent DDL operation finishes.

Example

To add a shard, specify the name of the replica set and the hostname of at least one member of the replica set, as a seed. If you specify additional hostnames, all must be members of the same replica set.

The following example adds a replica set named repl0 and specifies one member of the replica set:

sh.addShard("repl0/mongodb3.example.net:27327")

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