[CCR] Add get auto follow pattern api (#33849)

Relates to #33007

x-pack/plugin/ccr/qa/rest/src/test/resources/rest-api-spec/test/ccr/auto_follow.yml

@@ -5,9 +5,26 @@
         leader_cluster_alias: _local_
         body:
           leader_index_patterns: ['logs-*']
+          max_concurrent_read_batches: 2
   - is_true: acknowledged
 
+  - do:
+      ccr.get_auto_follow_pattern:
+        leader_cluster_alias: _local_
+  - match: { _local_.leader_index_patterns: ['logs-*'] }
+  - match: { _local_.max_concurrent_read_batches: 2 }
+
+  - do:
+      ccr.get_auto_follow_pattern: {}
+  - match: { _local_.leader_index_patterns: ['logs-*'] }
+  - match: { _local_.max_concurrent_read_batches: 2 }
+
   - do:
       ccr.delete_auto_follow_pattern:
         leader_cluster_alias: _local_
   - is_true: acknowledged
+
+  - do:
+      catch: missing
+      ccr.get_auto_follow_pattern:
+        leader_cluster_alias: _local_

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/Ccr.java

@@ -40,10 +40,13 @@
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.watcher.ResourceWatcherService;
 import org.elasticsearch.xpack.ccr.action.AutoFollowCoordinator;
+import org.elasticsearch.xpack.ccr.action.TransportGetAutoFollowPatternAction;
+import org.elasticsearch.xpack.ccr.rest.RestGetAutoFollowPatternAction;
 import org.elasticsearch.xpack.ccr.action.TransportAutoFollowStatsAction;
 import org.elasticsearch.xpack.ccr.rest.RestAutoFollowStatsAction;
 import org.elasticsearch.xpack.core.ccr.action.AutoFollowStatsAction;
 import org.elasticsearch.xpack.core.ccr.action.DeleteAutoFollowPatternAction;
+import org.elasticsearch.xpack.core.ccr.action.GetAutoFollowPatternAction;
 import org.elasticsearch.xpack.core.ccr.action.PutAutoFollowPatternAction;
 import org.elasticsearch.xpack.ccr.action.ShardChangesAction;
 import org.elasticsearch.xpack.ccr.action.ShardFollowTask;
@@ -163,7 +166,8 @@ public List<PersistentTasksExecutor<?>> getPersistentTasksExecutor(ClusterServic
                 new ActionHandler<>(UnfollowIndexAction.INSTANCE, TransportUnfollowIndexAction.class),
                 // auto-follow actions
                 new ActionHandler<>(DeleteAutoFollowPatternAction.INSTANCE, TransportDeleteAutoFollowPatternAction.class),
-                new ActionHandler<>(PutAutoFollowPatternAction.INSTANCE, TransportPutAutoFollowPatternAction.class));
+                new ActionHandler<>(PutAutoFollowPatternAction.INSTANCE, TransportPutAutoFollowPatternAction.class),
+                new ActionHandler<>(GetAutoFollowPatternAction.INSTANCE, TransportGetAutoFollowPatternAction.class));
     }
 
     public List<RestHandler> getRestHandlers(Settings settings, RestController restController, ClusterSettings clusterSettings,
@@ -184,7 +188,8 @@ public List<RestHandler> getRestHandlers(Settings settings, RestController restC
                 new RestUnfollowIndexAction(settings, restController),
                 // auto-follow APIs
                 new RestDeleteAutoFollowPatternAction(settings, restController),
-                new RestPutAutoFollowPatternAction(settings, restController));
+                new RestPutAutoFollowPatternAction(settings, restController),
+                new RestGetAutoFollowPatternAction(settings, restController));
     }
 
     public List<NamedWriteableRegistry.Entry> getNamedWriteables() {

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/action/TransportGetAutoFollowPatternAction.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.ccr.action;
+
+import org.elasticsearch.ResourceNotFoundException;
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.support.ActionFilters;
+import org.elasticsearch.action.support.master.TransportMasterNodeReadAction;
+import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.block.ClusterBlockException;
+import org.elasticsearch.cluster.block.ClusterBlockLevel;
+import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
+import org.elasticsearch.cluster.metadata.MetaData;
+import org.elasticsearch.cluster.service.ClusterService;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.threadpool.ThreadPool;
+import org.elasticsearch.transport.TransportService;
+import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata;
+import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata.AutoFollowPattern;
+import org.elasticsearch.xpack.core.ccr.action.GetAutoFollowPatternAction;
+
+import java.util.Collections;
+import java.util.Map;
+
+public class TransportGetAutoFollowPatternAction
+    extends TransportMasterNodeReadAction<GetAutoFollowPatternAction.Request, GetAutoFollowPatternAction.Response> {
+
+    @Inject
+    public TransportGetAutoFollowPatternAction(Settings settings,
+                                               TransportService transportService,
+                                               ClusterService clusterService,
+                                               ThreadPool threadPool,
+                                               ActionFilters actionFilters,
+                                               IndexNameExpressionResolver indexNameExpressionResolver) {
+        super(settings, GetAutoFollowPatternAction.NAME, transportService, clusterService, threadPool, actionFilters,
+            GetAutoFollowPatternAction.Request::new, indexNameExpressionResolver);
+    }
+
+    @Override
+    protected String executor() {
+        return ThreadPool.Names.SAME;
+    }
+
+    @Override
+    protected GetAutoFollowPatternAction.Response newResponse() {
+        return new GetAutoFollowPatternAction.Response();
+    }
+
+    @Override
+    protected void masterOperation(GetAutoFollowPatternAction.Request request,
+                                   ClusterState state,
+                                   ActionListener<GetAutoFollowPatternAction.Response> listener) throws Exception {
+        Map<String, AutoFollowPattern> autoFollowPatterns = getAutoFollowPattern(state.metaData(), request.getLeaderClusterAlias());
+        listener.onResponse(new GetAutoFollowPatternAction.Response(autoFollowPatterns));
+    }
+
+    @Override
+    protected ClusterBlockException checkBlock(GetAutoFollowPatternAction.Request request, ClusterState state) {
+        return state.blocks().globalBlockedException(ClusterBlockLevel.METADATA_READ);
+    }
+
+    static Map<String, AutoFollowPattern> getAutoFollowPattern(MetaData metaData, String leaderClusterAlias) {
+        AutoFollowMetadata autoFollowMetadata = metaData.custom(AutoFollowMetadata.TYPE);
+        if (autoFollowMetadata == null) {
+            throw new ResourceNotFoundException("no auto-follow patterns for cluster alias [{}] found", leaderClusterAlias);
+        }
+
+        if (leaderClusterAlias == null) {
+            return autoFollowMetadata.getPatterns();
+        }
+
+        AutoFollowPattern autoFollowPattern = autoFollowMetadata.getPatterns().get(leaderClusterAlias);
+        if (autoFollowPattern == null) {
+            throw new ResourceNotFoundException("no auto-follow patterns for cluster alias [{}] found", leaderClusterAlias);
+        }
+        return Collections.singletonMap(leaderClusterAlias, autoFollowPattern);
+    }
+}

x-pack/plugin/ccr/src/main/java/org/elasticsearch/xpack/ccr/rest/RestGetAutoFollowPatternAction.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.ccr.rest;
+
+import org.elasticsearch.client.node.NodeClient;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.rest.BaseRestHandler;
+import org.elasticsearch.rest.RestController;
+import org.elasticsearch.rest.RestRequest;
+import org.elasticsearch.rest.action.RestToXContentListener;
+import org.elasticsearch.xpack.core.ccr.action.GetAutoFollowPatternAction.Request;
+
+import java.io.IOException;
+
+import static org.elasticsearch.xpack.core.ccr.action.GetAutoFollowPatternAction.INSTANCE;
+
+public class RestGetAutoFollowPatternAction extends BaseRestHandler {
+
+    public RestGetAutoFollowPatternAction(Settings settings, RestController controller) {
+        super(settings);
+        controller.registerHandler(RestRequest.Method.GET, "/_ccr/auto_follow/{leader_cluster_alias}", this);
+        controller.registerHandler(RestRequest.Method.GET, "/_ccr/auto_follow", this);
+    }
+
+    @Override
+    public String getName() {
+        return "ccr_get_auto_follow_pattern_action";
+    }
+
+    @Override
+    protected RestChannelConsumer prepareRequest(RestRequest restRequest, NodeClient client) throws IOException {
+        Request request = new Request();
+        request.setLeaderClusterAlias(restRequest.param("leader_cluster_alias"));
+        return channel -> client.execute(INSTANCE, request, new RestToXContentListener<>(channel));
+    }
+
+}

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/ccr/action/GetAutoFollowPatternRequestTests.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.ccr.action;
+
+import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.test.AbstractWireSerializingTestCase;
+import org.elasticsearch.xpack.core.ccr.action.GetAutoFollowPatternAction;
+
+public class GetAutoFollowPatternRequestTests extends AbstractWireSerializingTestCase<GetAutoFollowPatternAction.Request> {
+
+    @Override
+    protected Writeable.Reader<GetAutoFollowPatternAction.Request> instanceReader() {
+        return GetAutoFollowPatternAction.Request::new;
+    }
+
+    @Override
+    protected GetAutoFollowPatternAction.Request createTestInstance() {
+        GetAutoFollowPatternAction.Request request = new GetAutoFollowPatternAction.Request();
+        if (randomBoolean()) {
+            request.setLeaderClusterAlias(randomAlphaOfLength(4));
+        }
+        return request;
+    }
+}

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/ccr/action/GetAutoFollowPatternResponseTests.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.ccr.action;
+
+import org.elasticsearch.common.unit.TimeValue;
+import org.elasticsearch.test.AbstractStreamableTestCase;
+import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata.AutoFollowPattern;
+import org.elasticsearch.xpack.core.ccr.action.GetAutoFollowPatternAction;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+public class GetAutoFollowPatternResponseTests extends AbstractStreamableTestCase<GetAutoFollowPatternAction.Response> {
+
+    @Override
+    protected GetAutoFollowPatternAction.Response createBlankInstance() {
+        return new GetAutoFollowPatternAction.Response();
+    }
+
+    @Override
+    protected GetAutoFollowPatternAction.Response createTestInstance() {
+        int numPatterns = randomIntBetween(1, 8);
+        Map<String, AutoFollowPattern> patterns = new HashMap<>(numPatterns);
+        for (int i = 0; i < numPatterns; i++) {
+            AutoFollowPattern autoFollowPattern = new AutoFollowPattern(
+                Collections.singletonList(randomAlphaOfLength(4)),
+                randomAlphaOfLength(4),
+                randomIntBetween(0, Integer.MAX_VALUE),
+                randomIntBetween(0, Integer.MAX_VALUE),
+                randomNonNegativeLong(),
+                randomIntBetween(0, Integer.MAX_VALUE),
+                randomIntBetween(0, Integer.MAX_VALUE),
+                TimeValue.timeValueMillis(500),
+                TimeValue.timeValueMillis(500));
+            patterns.put(randomAlphaOfLength(4), autoFollowPattern);
+        }
+        return new GetAutoFollowPatternAction.Response(patterns);
+    }
+}

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/ccr/action/TransportGetAutoFollowPatternActionTests.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.ccr.action;
+
+import org.elasticsearch.ResourceNotFoundException;
+import org.elasticsearch.cluster.metadata.MetaData;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata;
+import org.elasticsearch.xpack.core.ccr.AutoFollowMetadata.AutoFollowPattern;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.collection.IsMapContaining.hasEntry;
+
+public class TransportGetAutoFollowPatternActionTests extends ESTestCase {
+
+    public void testGetAutoFollowPattern() {
+        Map<String, AutoFollowPattern> patterns = new HashMap<>();
+        patterns.put("test_alias1",
+            new AutoFollowPattern(Collections.singletonList("index-*"), null, null, null, null, null, null, null, null));
+        patterns.put("test_alias2",
+            new AutoFollowPattern(Collections.singletonList("index-*"), null, null, null, null, null, null, null, null));
+        MetaData metaData = MetaData.builder()
+            .putCustom(AutoFollowMetadata.TYPE, new AutoFollowMetadata(patterns, Collections.emptyMap(), Collections.emptyMap()))
+            .build();
+
+        Map<String, AutoFollowPattern> result = TransportGetAutoFollowPatternAction.getAutoFollowPattern(metaData, "test_alias1");
+        assertThat(result.size(), equalTo(1));
+        assertThat(result, hasEntry("test_alias1", patterns.get("test_alias1")));
+
+        result = TransportGetAutoFollowPatternAction.getAutoFollowPattern(metaData, null);
+        assertThat(result.size(), equalTo(2));
+        assertThat(result, hasEntry("test_alias1", patterns.get("test_alias1")));
+        assertThat(result, hasEntry("test_alias2", patterns.get("test_alias2")));
+
+        expectThrows(ResourceNotFoundException.class,
+            () -> TransportGetAutoFollowPatternAction.getAutoFollowPattern(metaData, "another_alias"));
+    }
+
+    public void testGetAutoFollowPatternNoAutoFollowPatterns() {
+        AutoFollowMetadata autoFollowMetadata =
+            new AutoFollowMetadata(Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap());
+        MetaData metaData = MetaData.builder()
+            .putCustom(AutoFollowMetadata.TYPE, autoFollowMetadata)
+            .build();
+        expectThrows(ResourceNotFoundException.class,
+            () -> TransportGetAutoFollowPatternAction.getAutoFollowPattern(metaData, "test_alias"));
+    }
+
+    public void testGetAutoFollowPatternNoAutoFollowMetadata() {
+        MetaData metaData = MetaData.builder().build();
+        expectThrows(ResourceNotFoundException.class,
+            () -> TransportGetAutoFollowPatternAction.getAutoFollowPattern(metaData, "test_alias"));
+    }
+
+}

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowMetadata.java

@@ -170,8 +170,8 @@ public int hashCode() {
 
     public static class AutoFollowPattern implements Writeable, ToXContentObject {
 
-        private static final ParseField LEADER_PATTERNS_FIELD = new ParseField("leader_patterns");
-        private static final ParseField FOLLOW_PATTERN_FIELD = new ParseField("follow_pattern");
+        public static final ParseField LEADER_PATTERNS_FIELD = new ParseField("leader_index_patterns");
+        public static final ParseField FOLLOW_PATTERN_FIELD = new ParseField("follow_index_pattern");
         public static final ParseField MAX_BATCH_OPERATION_COUNT = new ParseField("max_batch_operation_count");
         public static final ParseField MAX_CONCURRENT_READ_BATCHES = new ParseField("max_concurrent_read_batches");
         public static final ParseField MAX_BATCH_SIZE_IN_BYTES = new ParseField("max_batch_size_in_bytes");