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[].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 (note 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; note that 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

Authorization

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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.

Example

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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,
          "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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