Get follower stats API | Elasticsearch Guide [7.5]

IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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Get follower stats APIedit

Get follower stats.

Requestedit

GET /<index>/_ccr/stats

Prerequisitesedit

If the Elasticsearch security features are enabled, you must have monitor cluster privileges on the cluster that contains the follower index. For more information, see Security privileges.

Descriptionedit

This API gets follower stats. This API will return shard-level stats about the following tasks associated with each shard for the specified indices.

Path parametersedit

<index>: (Required, string) A comma-delimited list of index patterns.

Response bodyedit

This API returns the following information:

indices: (array) An array of follower index statistics.

The indices array consists of objects containing two fields:

indices[].index: (string) The name of the follower index.
indices[].shards: (array) An array of shard-level following task statistics.

The shards array consists of objects containing the following fields:

indices[].shards[].remote_cluster: (string) The remote cluster containing the leader index.
indices[].shards[].leader_index: (string) The name of the index in the leader cluster being followed.
indices[].shards[].follower_index: (string) The name of the follower index.
indices[].shards[].shard_id: (integer) The numerical shard ID, with values from 0 to one less than the number of replicas.
indices[].shards[].leader_global_checkpoint: (long) The current global checkpoint on the leader known to the follower task.
indices[].shards[].leader_max_seq_no: (long) The current maximum sequence number on the leader known to the follower task.
indices[].shards[].follower_global_checkpoint: (long) The current global checkpoint on the follower. The difference between the leader_global_checkpoint and the follower_global_checkpoint is an indication of how much the follower is lagging the leader.
indices[].shards[].follower_max_seq_no: (long) The current maximum sequence number on the follower.
indices[].shards[].last_requested_seq_no: (long) The starting sequence number of the last batch of operations requested from the leader.
indices[].shards[].outstanding_read_requests: (integer) The number of active read requests from the follower.
indices[].shards[].outstanding_write_requests: (integer) The number of active bulk write requests on the follower.
indices[].shards[].write_buffer_operation_count: (integer) The number of write operations queued on the follower.
indices[].shards[].follower_mapping_version: (long) The mapping version the follower is synced up to.
indices[].shards[].follower_settings_version: (long) The index settings version the follower is synced up to.
indices[].shards[].follower_aliases_version: (long) The index aliases version the follower is synced up to.
indices[].shards[].total_read_time_millis: (long) The total time reads were outstanding, measured from the time a read was sent to the leader to the time a reply was returned to the follower.
indices[].shards[].total_read_remote_exec_time_millis: (long) The total time reads spent executing on the remote cluster.
indices[].shards[].successful_read_requests: (long) The number of successful fetches.
indices[].shards[].failed_read_requests: (long) The number of failed reads.
indices[].shards[].operations_read: (long) The total number of operations read from the leader.
indices[].shards[].bytes_read: (long) The total of transferred bytes read from the leader.

This is only an estimate and does not account for compression if enabled.
indices[].shards[].total_write_time_millis: (long) The total time spent writing on the follower.
indices[].shards[].write_buffer_size_in_bytes: (long) The total number of bytes of operations currently queued for writing.
indices[].shards[].successful_write_requests: (long) The number of bulk write requests executed on the follower.
indices[].shards[].failed_write_requests: (long) The number of failed bulk write requests executed on the follower.
indices[].shards[].operations_written: (long) The number of operations written on the follower.
indices[].shards[].read_exceptions: (array) An array of objects representing failed reads.

The read_exceptions array consists of objects containing the following fields:

indices[].shards[].read_exceptions[].from_seq_no: (long) The starting sequence number of the batch requested from the leader.
indices[].shards[].read_exceptions[].retries: (integer) The number of times the batch has been retried.
indices[].shards[].read_exceptions[].exception: (object) Represents the exception that caused the read to fail.

Continuing with the fields from shards:

indices[].shards[].time_since_last_read_millis: (long) The number of milliseconds since a read request was sent to the leader.

When the follower is caught up to the leader, this number will increase up to the configured read_poll_timeout at which point another read request will be sent to the leader.
indices[].fatal_exception: (object) An object representing a fatal exception that cancelled the following task. In this situation, the following task must be resumed manually with the resume follower API.

Examplesedit

This example retrieves follower stats:

GET /follower_index/_ccr/stats

The API returns the following results:

{
  "indices" : [
    {
      "index" : "follower_index",
      "shards" : [
        {
          "remote_cluster" : "remote_cluster",
          "leader_index" : "leader_index",
          "follower_index" : "follower_index",
          "shard_id" : 0,
          "leader_global_checkpoint" : 1024,
          "leader_max_seq_no" : 1536,
          "follower_global_checkpoint" : 768,
          "follower_max_seq_no" : 896,
          "last_requested_seq_no" : 897,
          "outstanding_read_requests" : 8,
          "outstanding_write_requests" : 2,
          "write_buffer_operation_count" : 64,
          "follower_mapping_version" : 4,
          "follower_settings_version" : 2,
          "follower_aliases_version" : 8,
          "total_read_time_millis" : 32768,
          "total_read_remote_exec_time_millis" : 16384,
          "successful_read_requests" : 32,
          "failed_read_requests" : 0,
          "operations_read" : 896,
          "bytes_read" : 32768,
          "total_write_time_millis" : 16384,
          "write_buffer_size_in_bytes" : 1536,
          "successful_write_requests" : 16,
          "failed_write_requests" : 0,
          "operations_written" : 832,
          "read_exceptions" : [ ],
          "time_since_last_read_millis" : 8
        }
      ]
    }
  ]
}

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