sh.addShardToZone()

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Definition

Behavior
Security
Example

Definition

sh.addShardToZone(shard, zone)

Associates a shard with a zone. MongoDB associates this shard with the given zone. Chunks that are covered by the zone are assigned to shards associated with the zone.

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 addShardToZone command.

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

This method has the following parameter:

Parameter	Type	Description
shard	string	The name of the shard to which to associate the zone.
zone	string	The name of the zone to associate with the shard.

Only issue sh.addShardToZone() when connected to a mongos instance.

Behavior

You can associate a zone with multiple shards, and a shard can associate with multiple zones.

See the zone manual page for more information on zones in sharded clusters.

Ranges

MongoDB effectively ignores zones that do not have at least one range of shard key values associated with it.

To associate a range of shard key values with a zone, use the sh.updateZoneKeyRange() method.

You can run updateZoneKeyRange database command and its helpers sh.updateZoneKeyRange() and sh.addTagRange() on an unsharded collection or a non-existing collection.

Tip

By defining the zones and the zone ranges before sharding an empty or a non-existing collection, the shard collection operation creates chunks for the defined zone ranges as well as any additional chunks to cover the entire range of the shard key values and performs an initial chunk distribution based on the zone ranges. This initial creation and distribution of chunks allows for faster setup of zoned sharding. After the initial distribution, the balancer manages the chunk distribution going forward.

See Pre-Define Zones and Zone Ranges for an Empty or Non-Existing Collection for an example.

Security

For sharded clusters that enforce access control, you must authenticate as a user whose privileges include either:

update on the shards collection in the config database; or, alternatively,
enableSharding on the cluster resource.

The clusterAdmin or clusterManager built-in roles have the appropriate permissions for issuing sh.addShardToZone(). See the Role-Based Access Control manual page for more information.

Example

The following example adds three zones, NYC, LAX, and NRT, associating each to a shard:

sh.addShardToZone("shard0000", "JFK")
sh.addShardToZone("shard0001", "LAX")
sh.addShardToZone("shard0002", "NRT")

A shard can associate with multiple zones. The following example associates LGA to shard0000:

sh.addShardToZone("shard0000", "LGA")

shard0000 associates with both the LGA zone and the JFK zone. In a balanced cluster, MongoDB routes reads and writes covered by either zone to shard0000.