OpenSearch/docs/reference/ccr/apis/follow/get-follow-info.asciidoc

[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]
--------------------------------------------------
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.

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

//Begin follower_indices
`follower_indices`::
(array) An array of follower index statistics.
+
.Properties of objects in `follower_indices`
[%collapsible%open]
====
`follower_index`::
(string) The name of the follower index.

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

//Begin parameters
`parameters`::
(object) An object that encapsulates {ccr} parameters. If the follower index's `status` is `paused`,
this object is omitted.
+
.Properties of `parameters`
[%collapsible%open]
=====
`max_outstanding_read_requests`::
(long) The maximum number of outstanding read requests from the remote cluster.

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

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

`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.

`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.

`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.

`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.

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

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

`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.
=====
//End parameters

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

`status`::
(string) Whether index following is `active` or `paused`.
====
//End follower_indices

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

This example retrieves follower info:

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

If the follower index is `active`, 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"
            }
        }
    ]
}
--------------------------------------------------

////
[source,console]
--------------------------------------------------
POST /follower_index/_ccr/pause_follow
--------------------------------------------------
// TEST[continued]

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

If the follower index is `paused`, the API returns the following results:

[source,console-result]
--------------------------------------------------
{
    "follower_indices" : [
        {
            "follower_index" : "follower_index",
            "remote_cluster" : "remote_cluster",
            "leader_index" : "leader_index",
            "status" : "paused"
        }
    ]
}
--------------------------------------------------