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Get follower stats API

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Get follower stats API

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Get follower stats.

Request

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GET /<index>/_ccr/stats

Prerequisites

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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.

Description

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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 parameters

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

Response body

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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.

Examples

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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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