Get follower stats API | Elasticsearch Guide

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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

indices

(array) An array of follower index statistics.

Properties of 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.
index: (string) The name of the follower index.

shards

(array) An array of shard-level following task statistics.

Properties of objects in 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.
failed_read_requests: (long) The number of failed reads.
failed_write_requests: (long) The number of failed bulk write requests executed on the follower.
follower_aliases_version: (long) The index aliases version the follower is synced up to.
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.
follower_index: (string) The name of the follower index.
follower_mapping_version: (long) The mapping version the follower is synced up to.
follower_max_seq_no: (long) The current maximum sequence number on the follower.
follower_settings_version: (long) The index settings version the follower is synced up to.
last_requested_seq_no: (long) The starting sequence number of the last batch of operations requested from the leader.
leader_global_checkpoint: (long) The current global checkpoint on the leader known to the follower task.
leader_index: (string) The name of the index in the leader cluster being followed.
leader_max_seq_no: (long) The current maximum sequence number on the leader known to the follower task.
operations_read: (long) The total number of operations read from the leader.
operations_written: (long) The number of operations written on the follower.
outstanding_read_requests: (integer) The number of active read requests from the follower.
outstanding_write_requests: (integer) The number of active bulk write requests on the follower.

read_exceptions

(array) An array of objects representing failed reads.

Properties of objects in read_exceptions

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

remote_cluster

(string) The remote cluster containing the leader index.

shard_id

(integer) The numerical shard ID, with values from 0 to one less than the number of replicas.

successful_read_requests

(long) The number of successful fetches.

successful_write_requests

(long) The number of bulk write requests executed on the follower.

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.

total_read_remote_exec_time_millis

(long) The total time reads spent executing on the remote cluster.

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.

total_write_time_millis

(long) The total time spent writing on the follower.

write_buffer_operation_count

(integer) The number of write operations queued on the follower.

write_buffer_size_in_bytes

(long) The total number of bytes of operations currently queued for writing.

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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