Introduce cross-cluster replication API docs

This commit is our first introduction to cross-cluster replication
docs. In this commit, we introduce the cross-cluster replication API
docs. We also add skelton docs for additional content that will be added
in a series of follow-up commits.

docs/build.gradle

@@ -149,7 +149,6 @@ buildRestTests.setups['host'] = '''
   - do:
       nodes.info:
         metric: [ http, transport ]
-  - is_true: nodes.$master.http.publish_address
   - set: {nodes.$master.http.publish_address: host}
   - set: {nodes.$master.transport.publish_address: transport_host}
 '''
@@ -1093,4 +1092,21 @@ buildRestTests.setups['calendar_outages_addevent'] = buildRestTests.setups['cale
            ]}
 '''
 
+buildRestTests.setups['leader_cluster'] = buildRestTests.setups['host'] + '''
+  - do:
+      cluster.put_settings:
+        body:
+          persistent:
+            cluster.remote.leader_cluster.seeds: $transport_host
+'''
 
+buildRestTests.setups['leader_cluster_and_leader_index'] = buildRestTests.setups['leader_cluster'] + '''
+  - do:
+      indices.create:
+        index: leader_index
+        body:
+          settings:
+            index.number_of_replicas: 0
+            index.number_of_shards: 1
+            index.soft_deletes.enabled: true
+'''

docs/reference/ccr/apis/auto-follow/delete-auto-follow-pattern.asciidoc

@@ -0,0 +1,67 @@
+[role="xpack"]
+[testenv="platinum"]
+[[ccr-delete-auto-follow-pattern]]
+=== Delete Auto-Follow Pattern API
+++++
+<titleabbrev>Delete Auto-Follow Pattern</titleabbrev>
+++++
+
+Delete auto-follow patterns.
+
+==== Description
+
+This API deletes configured auto-follow patterns.
+
+==== Request
+
+//////////////////////////
+
+[source,js]
+--------------------------------------------------
+PUT /_ccr/auto_follow/leader_cluster
+{
+  "leader_cluster" : "leader_cluster",
+  "leader_index_patterns" :
+  [
+    "leader_index"
+  ],
+  "follow_index_pattern" : "{{leader_index}}-follower"
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:leader_cluster]
+// TESTSETUP
+
+//////////////////////////
+
+[source,js]
+--------------------------------------------------
+DELETE /_ccr/auto_follow/<leader_cluster>
+--------------------------------------------------
+// CONSOLE
+// TEST[s/<leader_cluster>/leader_cluster/]
+
+Here, the auto-follow patterns associated with the
+<<modules-remote-clusters,remote cluster>> specified by `<leader_cluster>`
+will be deleted.
+
+==== Example
+
+The following is an example of using the delete auto-follow pattern API.
+
+[source,js]
+--------------------------------------------------
+DELETE /_ccr/auto_follow/leader_cluster
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:leader_cluster]
+
+The API returns the following result:
+
+[source,js]
+--------------------------------------------------
+{
+  "acknowledged" : true
+}
+--------------------------------------------------
+// TESTRESPONSE

docs/reference/ccr/apis/auto-follow/get-auto-follow-pattern.asciidoc

@@ -0,0 +1,91 @@
+[role="xpack"]
+[testenv="platinum"]
+[[ccr-get-auto-follow-pattern]]
+=== Get Auto-Follow Pattern API
+++++
+<titleabbrev>Get Auto-Follow Pattern</titleabbrev>
+++++
+
+Get auto-follow patterns.
+
+==== Description
+
+This API gets configured auto-follow patterns. This API will return the
+configured auto-follow patterns on a per-cluster basis.
+
+==== Request
+
+//////////////////////////
+
+[source,js]
+--------------------------------------------------
+PUT /_ccr/auto_follow/leader_cluster
+{
+  "leader_cluster" : "leader_cluster",
+  "leader_index_patterns" :
+  [
+    "leader_index*"
+  ],
+  "follow_index_pattern" : "{{leader_index}}-follower"
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:leader_cluster]
+// TESTSETUP
+
+[source,js]
+--------------------------------------------------
+DELETE /_ccr/auto_follow/leader_cluster
+--------------------------------------------------
+// CONSOLE
+// TEST
+// TEARDOWN
+
+//////////////////////////
+
+[source,js]
+--------------------------------------------------
+GET /_ccr/auto_follow/
+--------------------------------------------------
+// CONSOLE
+
+Here, all auto-follow patterns will be returned.
+
+[source,js]
+--------------------------------------------------
+GET /_ccr/auto_follow/<leader_cluster>
+--------------------------------------------------
+// CONSOLE
+// TEST[s/<leader_cluster>/leader_cluster/]
+
+Here, all auto-follow patterns configured for the
+<<modules-remote-clusters,remote cluster>> specified by `<leader_cluster>`
+will be returned.
+
+==== Example
+
+The following is an example of using the get auto-follow pattern API.
+
+[source,js]
+--------------------------------------------------
+GET /_ccr/auto_follow/leader_cluster
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:leader_cluster]
+
+The API returns the following result:
+
+[source,js]
+--------------------------------------------------
+{
+  "leader_cluster" :
+  {
+    "leader_index_patterns" :
+    [
+      "leader_index*"
+    ],
+    "follow_index_pattern" : "{{leader_index}}-follower"
+  }
+}
+--------------------------------------------------
+// TESTRESPONSE

docs/reference/ccr/apis/auto-follow/get-auto-follow-stats.asciidoc

@@ -0,0 +1,48 @@
+[role="xpack"]
+[testenv="platinum"]
+[[ccr-get-auto-follow-stats]]
+=== Get Auto-Follow Stats API
+++++
+<titleabbrev>Get Auto-Follow Stats</titleabbrev>
+++++
+
+Get auto-follow stats.
+
+==== Description
+
+This API gets stats about auto-follow patterns.
+
+==== Request
+
+[source,js]
+--------------------------------------------------
+GET /_ccr/auto_follow/stats
+--------------------------------------------------
+// CONSOLE
+// TEST
+
+Here, stats about auto-follow patterns will be returned.
+
+==== Example
+
+The following is an example of using the get auto-follow stats API.
+
+[source,js]
+--------------------------------------------------
+GET /_ccr/auto_follow/stats
+--------------------------------------------------
+// CONSOLE
+// TEST
+
+The API returns the following result:
+
+[source,js]
+--------------------------------------------------
+{
+  "number_of_successful_follow_indices" : 16,
+  "number_of_failed_follow_indices" : 0,
+  "number_of_failed_remote_cluster_state_requests" : 0,
+  "recent_auto_follow_errors" : [ ]
+}
+--------------------------------------------------
+// TESTRESPONSE[s/"number_of_successful_follow_indices" : 16/"number_of_successful_follow_indices" : $body.number_of_successful_follow_indices/]

docs/reference/ccr/apis/auto-follow/put-auto-follow-pattern.asciidoc

@@ -0,0 +1,98 @@
+[role="xpack"]
+[testenv="platinum"]
+[[ccr-put-auto-follow-pattern]]
+=== Create Auto-Follow Pattern API
+++++
+<titleabbrev>Create Auto-Follow Pattern</titleabbrev>
+++++
+
+Creates an auto-follow pattern.
+
+==== Description
+
+This API creates a new collection of auto-follow patterns against the specified
+remote cluster. Newly created indices on the remote cluster matching any of the specified
+patterns will be automatically configured as follower indices.
+
+==== Request
+
+[source,js]
+--------------------------------------------------
+PUT /_ccr/auto_follow/<leader_cluster>
+{
+  "leader_cluster" : "<leader_cluster>",
+  "leader_index_patterns" :
+  [
+    "<leader_index_pattern>"
+  ],
+  "follow_index_pattern" : "<follow_index_pattern>"
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:leader_cluster]
+// TEST[s/<leader_cluster>/leader_cluster/]
+// TEST[s/<leader_index_patterns>/leader_index*/]
+// TEST[s/<follow_index_pattern>/{{leader_index}}-follower/]
+
+Here, `<leader_cluster>` is the <<modules-remote-clusters,remote cluster>>
+containing the leader indices to match against, `<leader_index_pattern>` is a
+simple index pattern to match against indices in the remote cluster, and
+`<follow_index_pattern>` is the pattern to use to name the resulting follower
+indices. The `<follow_index_pattern>` can use the template `{{leader_index}}` to
+refer to the name of the leader index being followed.
+
+==== Request Body
+`leader_cluster`::
+  (required string) the <<modules-remote-clusters,remote cluster>> containing the
+  leader indices to match against
+
+`leader_index_patterns`::
+  (array) an array of simple index patterns to match against indices in the
+  remote cluster specified by the `leader_cluster` field
+
+`follow_index_pattern`::
+  (string) the name of follower index; the template `{{leader_index}}` can be
+  used to derive the name of the follower index from the name of the leader
+  index
+
+include::../follow-request-body.asciidoc[]
+
+==== Example
+
+The following is an example of using the create auto-follow pattern API.
+
+[source,js]
+--------------------------------------------------
+PUT /_ccr/auto_follow/leader_cluster
+{
+  "leader_cluster" : "leader_cluster",
+  "leader_index_patterns" :
+  [
+    "leader_index*"
+  ],
+  "follow_index_pattern" : "{{leader_index}}-follower"
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:leader_cluster]
+
+The API returns the following result:
+
+[source,js]
+--------------------------------------------------
+{
+  "acknowledged" : true
+}
+--------------------------------------------------
+// TESTRESPONSE
+
+//////////////////////////
+
+[source,js]
+--------------------------------------------------
+DELETE /_ccr/auto_follow/leader_cluster
+--------------------------------------------------
+// CONSOLE
+// TEST[continued]
+
+//////////////////////////

docs/reference/ccr/apis/ccr-apis.asciidoc

@@ -0,0 +1,38 @@
+[role="xpack"]
+[testenv="platinum"]
+[[ccr-apis]]
+== Cross-cluster replication APIs
+
+You can use the following APIs to perform {ccr} operations.
+
+[float]
+[[ccr-api-follow]]
+=== Follow
+
+* <<ccr-put-follow,Create follower index>>
+* <<ccr-post-pause-follow,Pause follower>>
+* <<ccr-post-resume-follow,Resume follower>>
+* <<ccr-post-unfollow,Convert follower index to a regular index>>
+* <<ccr-get-follow-stats,Get stats about follower indices>>
+
+[float]
+[[ccr-api-auto-follow]]
+=== Auto-follow
+
+* <<ccr-put-auto-follow-pattern,Create auto-follow pattern>>
+* <<ccr-delete-auto-follow-pattern,Delete auto-follow pattern>>
+* <<ccr-get-auto-follow-pattern,Get auto-follow patterns>>
+* <<ccr-get-auto-follow-stats,Get stats about auto-follow patterns>>
+
+// follow
+include::follow/put-follow.asciidoc[]
+include::follow/post-pause-follow.asciidoc[]
+include::follow/post-resume-follow.asciidoc[]
+include::follow/post-unfollow.asciidoc[]
+include::follow/get-follow-stats.asciidoc[]
+
+// auto-follow
+include::auto-follow/put-auto-follow-pattern.asciidoc[]
+include::auto-follow/delete-auto-follow-pattern.asciidoc[]
+include::auto-follow/get-auto-follow-pattern.asciidoc[]
+include::auto-follow/get-auto-follow-stats.asciidoc[]