[role="xpack"]
[testenv="platinum"]
[[ccr-get-follow-info]]
=== Get follower info API
++++
<titleabbrev>Get follower info</titleabbrev>
++++

Retrieves information about all follower indices.

[[ccr-get-follow-info-request]]
==== {api-request-title}

//////////////////////////

[source,console]
--------------------------------------------------
PUT /follower_index/_ccr/follow?wait_for_active_shards=1
{
  "remote_cluster" : "remote_cluster",
  "leader_index" : "leader_index"
}
--------------------------------------------------
// TESTSETUP
// TEST[setup:remote_cluster_and_leader_index]

[source,console]
--------------------------------------------------
POST /follower_index/_ccr/pause_follow
--------------------------------------------------
// TEARDOWN

//////////////////////////

[source,console]
--------------------------------------------------
GET /<index>/_ccr/info
--------------------------------------------------
// TEST[s/<index>/follower_index/]

[[ccr-get-follow-info-prereqs]]
==== {api-prereq-title}

* If the {es} {security-features} are enabled, you must have `monitor` cluster
privileges. For more information, see <<security-privileges>>.

[[ccr-get-follow-info-desc]]
==== {api-description-title}

This API lists the parameters and the status for each follower index.
For example, the results include follower index names, leader index names,
replication options and whether the follower indices are active or paused.

[[ccr-get-follow-info-path-parms]]
==== {api-path-parms-title}

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

[[ccr-get-follow-info-response-body]]
==== {api-response-body-title}

This API returns the following information:

`follower_indices`::
  (array) An array of follower index statistics.

The `indices` array consists of objects containing several fields:

`indices[].follower_index`::
  (string) The name of the follower index.

`indices[].remote_cluster`::
  (string) The <<modules-remote-clusters,remote cluster>> that contains the
  leader index.

`indices[].leader_index`::
  (string) The name of the index in the leader cluster that is followed.

`indices[].status`::
  (string) Whether index following is `active` or `paused`. 

`indices[].parameters`::
  (object) An object that encapsulates {ccr} parameters.

The `parameters` contains the following fields:

`indices[].parameters.max_read_request_operation_count`::
  (integer) The maximum number of operations to pull per read from the remote
  cluster.

`indices[].parameters.max_outstanding_read_requests`::
  (long) The maximum number of outstanding read requests from the remote cluster.

`indices[].parameters.max_read_request_size`::
  (<<byte-units,byte value>>) The maximum size in bytes of per read of a batch
  of operations pulled from the remote cluster.

`indices[].parameters.max_write_request_operation_count`::
  (integer) The maximum number of operations per bulk write request executed on
  the follower.

`indices[].parameters.max_write_request_size`::
  (<<byte-units,byte value>>) The maximum total bytes of operations per bulk
  write request executed on the follower.

`indices[].parameters.max_outstanding_write_requests`::
  (integer) The maximum number of outstanding write requests on the follower.

`indices[].parameters.max_write_buffer_count`::
  (integer) The maximum number of operations that can be queued for writing.
  When this limit is reached, reads from the remote cluster are deferred until
  the number of queued operations goes below the limit.

`indices[].parameters.max_write_buffer_size`::
  (<<byte-units,byte value>>) The maximum total bytes of operations that can be
  queued for writing. When this limit is reached, reads from the remote cluster
  are deferred until the total bytes of queued operations goes below the limit.

`indices[].parameters.max_retry_delay`::
  (<<time-units,time value>>) The maximum time to wait before retrying an
  operation that failed exceptionally. An exponential backoff strategy is
  employed when retrying.

`indices[].parameters.read_poll_timeout`::
  (<<time-units,time value>>) The maximum time to wait for new operations on the
  remote cluster when the follower index is synchronized with the leader index.
  When the timeout has elapsed, the poll for operations returns to the follower
  so that it can update some statistics, then the follower immediately attempts
  to read from the leader again.

[[ccr-get-follow-info-examples]]
==== {api-examples-title}

This example retrieves follower info:

[source,console]
--------------------------------------------------
GET /follower_index/_ccr/info
--------------------------------------------------

The API returns the following results:

[source,console-result]
--------------------------------------------------
{
    "follower_indices" : [
        {
            "follower_index" : "follower_index",
            "remote_cluster" : "remote_cluster",
            "leader_index" : "leader_index",
            "status" : "active",
            "parameters" : {
                "max_read_request_operation_count" : 5120,
                "max_read_request_size" : "32mb",
                "max_outstanding_read_requests" : 12,
                "max_write_request_operation_count" : 5120,
                "max_write_request_size" : "9223372036854775807b",
                "max_outstanding_write_requests" : 9,
                "max_write_buffer_count" : 2147483647,
                "max_write_buffer_size" : "512mb",
                "max_retry_delay" : "500ms",
                "read_poll_timeout" : "1m"
            }
        }
    ]
}
--------------------------------------------------