[HLRC] Added support for Follow Stats API

client/rest-high-level/src/main/java/org/elasticsearch/client/CcrClient.java

@@ -23,6 +23,8 @@
 import org.elasticsearch.client.ccr.CcrStatsRequest;
 import org.elasticsearch.client.ccr.CcrStatsResponse;
 import org.elasticsearch.client.ccr.DeleteAutoFollowPatternRequest;
+import org.elasticsearch.client.ccr.FollowStatsRequest;
+import org.elasticsearch.client.ccr.FollowStatsResponse;
 import org.elasticsearch.client.ccr.GetAutoFollowPatternRequest;
 import org.elasticsearch.client.ccr.GetAutoFollowPatternResponse;
 import org.elasticsearch.client.ccr.PauseFollowRequest;
@@ -385,7 +387,7 @@ public CcrStatsResponse getCcrStats(CcrStatsRequest request,
     }
 
     /**
-     * Gets all CCR stats.
+     * Asynchronously gets all CCR stats.
      *
      * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-get-stats.html">
      * the docs</a> for more.
@@ -406,4 +408,48 @@ public void getCcrStatsAsync(CcrStatsRequest request,
         );
     }
 
+    /**
+     * Gets follow stats for specific indices.
+     *
+     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-get-follow-stats.html">
+     * the docs</a> for more.
+     *
+     * @param request the request
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @return the response
+     * @throws IOException in case there is a problem sending the request or parsing back the response
+     */
+    public FollowStatsResponse getFollowStats(FollowStatsRequest request,
+                                              RequestOptions options) throws IOException {
+        return restHighLevelClient.performRequestAndParseEntity(
+            request,
+            CcrRequestConverters::getFollowStats,
+            options,
+            FollowStatsResponse::fromXContent,
+            Collections.emptySet()
+        );
+    }
+
+    /**
+     * Asynchronously gets follow stats for specific indices.
+     *
+     * See <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/ccr-get-follow-stats.html">
+     * the docs</a> for more.
+     *
+     * @param request the request
+     * @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     */
+    public void getFollowStatsAsync(FollowStatsRequest request,
+                                    RequestOptions options,
+                                    ActionListener<FollowStatsResponse> listener) {
+        restHighLevelClient.performRequestAsyncAndParseEntity(
+            request,
+            CcrRequestConverters::getFollowStats,
+            options,
+            FollowStatsResponse::fromXContent,
+            listener,
+            Collections.emptySet()
+        );
+    }
+
 }

client/rest-high-level/src/main/java/org/elasticsearch/client/CcrRequestConverters.java

@@ -25,6 +25,7 @@
 import org.apache.http.client.methods.HttpPut;
 import org.elasticsearch.client.ccr.CcrStatsRequest;
 import org.elasticsearch.client.ccr.DeleteAutoFollowPatternRequest;
+import org.elasticsearch.client.ccr.FollowStatsRequest;
 import org.elasticsearch.client.ccr.GetAutoFollowPatternRequest;
 import org.elasticsearch.client.ccr.PauseFollowRequest;
 import org.elasticsearch.client.ccr.PutAutoFollowPatternRequest;
@@ -108,4 +109,12 @@ static Request getCcrStats(CcrStatsRequest ccrStatsRequest) {
         return new Request(HttpGet.METHOD_NAME, endpoint);
     }
 
+    static Request getFollowStats(FollowStatsRequest followStatsRequest) {
+        String endpoint = new RequestConverters.EndpointBuilder()
+            .addPathPart(followStatsRequest.getFollowerIndex())
+            .addPathPartAsIs("_ccr", "stats")
+            .build();
+        return new Request(HttpGet.METHOD_NAME, endpoint);
+    }
+
 }

client/rest-high-level/src/main/java/org/elasticsearch/client/ccr/FollowStatsRequest.java

@@ -0,0 +1,37 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.client.ccr;
+
+import org.elasticsearch.client.Validatable;
+
+import java.util.Objects;
+
+public final class FollowStatsRequest implements Validatable {
+
+    private final String followerIndex;
+
+    public FollowStatsRequest(String followerIndex) {
+        this.followerIndex = Objects.requireNonNull(followerIndex);
+    }
+
+    public String getFollowerIndex() {
+        return followerIndex;
+    }
+}

client/rest-high-level/src/main/java/org/elasticsearch/client/ccr/FollowStatsResponse.java

@@ -0,0 +1,39 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.client.ccr;
+
+import org.elasticsearch.common.xcontent.XContentParser;
+
+public final class FollowStatsResponse {
+
+    public static FollowStatsResponse fromXContent(XContentParser parser) {
+        return new FollowStatsResponse(IndicesFollowStats.PARSER.apply(parser, null));
+    }
+
+    private final IndicesFollowStats indicesFollowStats;
+
+    public FollowStatsResponse(IndicesFollowStats indicesFollowStats) {
+        this.indicesFollowStats = indicesFollowStats;
+    }
+
+    public IndicesFollowStats getIndicesFollowStats() {
+        return indicesFollowStats;
+    }
+}

client/rest-high-level/src/test/java/org/elasticsearch/client/CCRIT.java

@@ -32,6 +32,8 @@
 import org.elasticsearch.client.ccr.CcrStatsRequest;
 import org.elasticsearch.client.ccr.CcrStatsResponse;
 import org.elasticsearch.client.ccr.DeleteAutoFollowPatternRequest;
+import org.elasticsearch.client.ccr.FollowStatsRequest;
+import org.elasticsearch.client.ccr.FollowStatsResponse;
 import org.elasticsearch.client.ccr.GetAutoFollowPatternRequest;
 import org.elasticsearch.client.ccr.GetAutoFollowPatternResponse;
 import org.elasticsearch.client.ccr.IndicesFollowStats.ShardFollowStats;
@@ -107,9 +109,10 @@ public void testIndexFollowing() throws Exception {
         assertThat(leaderSearchResponse.getHits().getTotalHits().value, equalTo(1L));
 
         assertBusy(() -> {
-            CcrStatsRequest ccrStatsRequest = new CcrStatsRequest();
-            CcrStatsResponse ccrStatsResponse = execute(ccrStatsRequest, ccrClient::getCcrStats, ccrClient::getCcrStatsAsync);
-            List<ShardFollowStats> shardFollowStats = ccrStatsResponse.getIndicesFollowStats().getShardFollowStats("follower");
+            FollowStatsRequest followStatsRequest = new FollowStatsRequest("follower");
+            FollowStatsResponse followStatsResponse =
+                execute(followStatsRequest, ccrClient::getFollowStats, ccrClient::getFollowStatsAsync);
+            List<ShardFollowStats> shardFollowStats = followStatsResponse.getIndicesFollowStats().getShardFollowStats("follower");
             long followerGlobalCheckpoint = shardFollowStats.stream()
                 .mapToLong(ShardFollowStats::getFollowerGlobalCheckpoint)
                 .max()
@@ -132,9 +135,10 @@ public void testIndexFollowing() throws Exception {
         assertThat(resumeFollowResponse.isAcknowledged(), is(true));
 
         assertBusy(() -> {
-            CcrStatsRequest ccrStatsRequest = new CcrStatsRequest();
-            CcrStatsResponse ccrStatsResponse = execute(ccrStatsRequest, ccrClient::getCcrStats, ccrClient::getCcrStatsAsync);
-            List<ShardFollowStats> shardFollowStats = ccrStatsResponse.getIndicesFollowStats().getShardFollowStats("follower");
+            FollowStatsRequest followStatsRequest = new FollowStatsRequest("follower");
+            FollowStatsResponse followStatsResponse =
+                execute(followStatsRequest, ccrClient::getFollowStats, ccrClient::getFollowStatsAsync);
+            List<ShardFollowStats> shardFollowStats = followStatsResponse.getIndicesFollowStats().getShardFollowStats("follower");
             long followerGlobalCheckpoint = shardFollowStats.stream()
                 .mapToLong(ShardFollowStats::getFollowerGlobalCheckpoint)
                 .max()

client/rest-high-level/src/test/java/org/elasticsearch/client/ccr/CcrStatsResponseTests.java

@@ -323,7 +323,7 @@ private static AutoFollowStats randomAutoFollowStats() {
         );
     }
 
-    private static IndicesFollowStats randomIndicesFollowStats() {
+    static IndicesFollowStats randomIndicesFollowStats() {
         int numIndices = randomIntBetween(0, 16);
         NavigableMap<String, List<ShardFollowStats>> shardFollowStats = new TreeMap<>();
         for (int i = 0; i < numIndices; i++) {