OPTIONS

Manage Shard Tags

In a sharded cluster, you can use tags to associate specific ranges of a shard key with a specific shard or subset of shards.

Tag a Shard

Associate tags with a particular shard using the sh.addShardTag() method when connected to a mongos instance. A single shard may have multiple tags, and multiple shards may also have the same tag.

Example

The following example adds the tag NYC to two shards, and the tags SFO and NRT to a third shard:

sh.addShardTag("shard0000", "NYC")
sh.addShardTag("shard0001", "NYC")
sh.addShardTag("shard0002", "SFO")
sh.addShardTag("shard0002", "NRT")

You may remove tags from a particular shard using the sh.removeShardTag() method when connected to a mongos instance, as in the following example, which removes the NRT tag from a shard:

sh.removeShardTag("shard0002", "NRT")

Tag a Shard Key Range

To assign a tag to a range of shard keys use the sh.addTagRange() method when connected to a mongos instance. Any given shard key range may only have one assigned tag. You cannot overlap defined ranges, or tag the same range more than once.

Example

Given a collection named users in the records database, sharded by the zipcode field. The following operations assign:

  • two ranges of zip codes in Manhattan and Brooklyn the NYC tag
  • one range of zip codes in San Francisco the SFO tag
sh.addTagRange("records.users", { zipcode: "10001" }, { zipcode: "10281" }, "NYC")
sh.addTagRange("records.users", { zipcode: "11201" }, { zipcode: "11240" }, "NYC")
sh.addTagRange("records.users", { zipcode: "94102" }, { zipcode: "94135" }, "SFO")

Note

Remove a Tag From a Shard Key Range

The mongod does not provide a helper for removing a tag range. You may delete tag assignment from a shard key range by removing the corresponding document from the tags collection of the config database.

Each document in the tags holds the namespace of the sharded collection and a minimum shard key value.

Example

The following example removes the NYC tag assignment for the range of zip codes within Manhattan:

use config
db.tags.remove({ _id: { ns: "records.users", min: { zipcode: "10001" }}, tag: "NYC" })

View Existing Shard Tags

The output from sh.status() lists tags associated with a shard, if any, for each shard. A shard’s tags exist in the shard’s document in the shards collection of the config database. To return all shards with a specific tag, use a sequence of operations that resemble the following, which will return only those shards tagged with NYC:

use config
db.shards.find({ tags: "NYC" })

You can find tag ranges for all namespaces in the tags collection of the config database. The output of sh.status() displays all tag ranges. To return all shard key ranges tagged with NYC, use the following sequence of operations:

use config
db.tags.find({ tags: "NYC" })