Shard Management Commands

SPLITSHARD: Split a Shard

/admin/collections?action=SPLITSHARD&collection=name&shard=shardID

Splitting a shard will take an existing shard and break it into two pieces which are written to disk as two (new) shards. The original shard will continue to contain the same data as-is but it will start re-routing requests to the new shards. The new shards will have as many replicas as the original shard. A soft commit is automatically issued after splitting a shard so that documents are made visible on sub-shards. An explicit commit (hard or soft) is not necessary after a split operation because the index is automatically persisted to disk during the split operation.

This command allows for seamless splitting and requires no downtime. A shard being split will continue to accept query and indexing requests and will automatically start routing requests to the new shards once this operation is complete. This command can only be used for SolrCloud collections created with numShards parameter, meaning collections which rely on Solr’s hash-based routing mechanism.

The split is performed by dividing the original shard’s hash range into two equal partitions and dividing up the documents in the original shard according to the new sub-ranges. Two parameters discussed below, ranges and split.key provide further control over how the split occurs.

The newly created shards will have as many replicas as the parent shard, of the same replica types.

When using splitMethod=rewrite (default) you must ensure that the node running the leader of the parent shard has enough free disk space i.e., more than twice the index size, for the split to succeed. The API uses the Autoscaling framework to find nodes that can satisfy the disk requirements for the new replicas but only when an Autoscaling policy is configured. Refer to Autoscaling Policy and Preferences section for more details.

Also, the first replicas of resulting sub-shards will always be placed on the shard leader node, which may cause Autoscaling policy violations that need to be resolved either automatically (when appropriate triggers are in use) or manually.

Shard splitting can be a long running process. In order to avoid timeouts, you should run this as an asynchronous call.

http://localhost:8983/solr/admin/collections?action=SPLITSHARD&collection=anotherCollection&shard=shard1&wt=xml

<response>
  <lst name="responseHeader">
    <int name="status">0</int>
    <int name="QTime">6120</int>
  </lst>
  <lst name="success">
    <lst>
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">3673</int>
      </lst>
      <str name="core">anotherCollection_shard1_1_replica1</str>
    </lst>
    <lst>
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">3681</int>
      </lst>
      <str name="core">anotherCollection_shard1_0_replica1</str>
    </lst>
    <lst>
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">6008</int>
      </lst>
    </lst>
    <lst>
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">6007</int>
      </lst>
    </lst>
    <lst>
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">71</int>
      </lst>
    </lst>
    <lst>
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">0</int>
      </lst>
      <str name="core">anotherCollection_shard1_1_replica1</str>
      <str name="status">EMPTY_BUFFER</str>
    </lst>
    <lst>
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">0</int>
      </lst>
      <str name="core">anotherCollection_shard1_0_replica1</str>
      <str name="status">EMPTY_BUFFER</str>
    </lst>
  </lst>
</response>

CREATESHARD: Create a Shard

Shards can only created with this API for collections that use the 'implicit' router (i.e., when the collection was created, router.name=implicit). A new shard with a name can be created for an existing 'implicit' collection.

Use SPLITSHARD for collections created with the 'compositeId' router (router.key=compositeId).

/admin/collections?action=CREATESHARD&shard=shardName&collection=name

The default values for replicationFactor or nrtReplicas, tlogReplicas, pullReplicas from the collection is used to determine the number of replicas to be created for the new shard. This can be customized by explicitly passing the corresponding parameters to the request.

The API uses the Autoscaling framework to find the best possible nodes in the cluster when an Autoscaling preferences or policy is configured. Refer to Autoscaling Policy and Preferences section for more details.

http://localhost:8983/solr/admin/collections?action=CREATESHARD&collection=anImplicitCollection&shard=shard-z&wt=xml

<response>
  <lst name="responseHeader">
    <int name="status">0</int>
    <int name="QTime">558</int>
  </lst>
</response>

DELETESHARD: Delete a Shard

Deleting a shard will unload all replicas of the shard, remove them from clusterstate.json, and (by default) delete the instanceDir and dataDir for each replica. It will only remove shards that are inactive, or which have no range given for custom sharding.

/admin/collections?action=DELETESHARD&shard=shardID&collection=name

http://localhost:8983/solr/admin/collections?action=DELETESHARD&collection=anotherCollection&shard=shard1&wt=xml

<response>
  <lst name="responseHeader">
    <int name="status">0</int>
    <int name="QTime">558</int>
  </lst>
  <lst name="success">
    <lst name="10.0.1.4:8983_solr">
      <lst name="responseHeader">
        <int name="status">0</int>
        <int name="QTime">27</int>
      </lst>
    </lst>
  </lst>
</response>

FORCELEADER: Force Shard Leader

In the unlikely event of a shard losing its leader, this command can be invoked to force the election of a new leader.

/admin/collections?action=FORCELEADER&collection=<collectionName>&shard=<shardName>