Add cross cluster support to _terms_enum (#73478)

This commit adds the support to search cross cluster indices (with the cross cluster syntax)
 in the _terms_enum API.

Relates #71550

x-pack/plugin/core/src/internalClusterTest/java/org/elasticsearch/xpack/core/termsenum/CCSTermsEnumIT.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+package org.elasticsearch.xpack.core.termsenum;
+
+import org.elasticsearch.client.Client;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.plugins.Plugin;
+import org.elasticsearch.test.AbstractMultiClustersTestCase;
+import org.elasticsearch.xpack.core.LocalStateCompositeXPackPlugin;
+import org.elasticsearch.xpack.core.termsenum.action.TermsEnumAction;
+import org.elasticsearch.xpack.core.termsenum.action.TermsEnumRequest;
+import org.elasticsearch.xpack.core.termsenum.action.TermsEnumResponse;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
+import static org.hamcrest.Matchers.equalTo;
+
+public class CCSTermsEnumIT extends AbstractMultiClustersTestCase {
+
+    @Override
+    protected Collection<String> remoteClusterAlias() {
+        return List.of("remote_cluster");
+    }
+
+    @Override
+    protected Collection<Class<? extends Plugin>> nodePlugins(String clusterAlias) {
+        final List<Class<? extends Plugin>> plugins = new ArrayList<>(super.nodePlugins(clusterAlias));
+        plugins.add(LocalStateCompositeXPackPlugin.class);
+        return plugins;
+    }
+
+    public void testBasic() {
+        Settings indexSettings = Settings.builder().put("index.number_of_replicas", 0).build();
+        final Client localClient = client(LOCAL_CLUSTER);
+        final Client remoteClient = client("remote_cluster");
+        String localIndex = "local_test";
+        assertAcked(localClient.admin().indices().prepareCreate(localIndex).setSettings(indexSettings));
+        localClient.prepareIndex(localIndex).setSource("foo", "foo").get();
+        localClient.prepareIndex(localIndex).setSource("foo", "foobar").get();
+        localClient.admin().indices().prepareRefresh(localIndex).get();
+
+        String remoteIndex = "remote_test";
+        assertAcked(remoteClient.admin().indices().prepareCreate(remoteIndex).setSettings(indexSettings));
+        remoteClient.prepareIndex(remoteIndex).setSource("foo", "bar").get();
+        remoteClient.prepareIndex(remoteIndex).setSource("foo", "foobar").get();
+        remoteClient.prepareIndex(remoteIndex).setSource("foo", "zar").get();
+        remoteClient.admin().indices().prepareRefresh(remoteIndex).get();
+
+        // _terms_enum on a remote cluster
+        TermsEnumRequest req = new TermsEnumRequest("remote_cluster:remote_test")
+            .field("foo.keyword");
+        TermsEnumResponse response = client().execute(TermsEnumAction.INSTANCE, req).actionGet();
+        assertTrue(response.isComplete());
+        assertThat(response.getTerms().size(), equalTo(3));
+        assertThat(response.getTerms().get(0), equalTo("bar"));
+        assertThat(response.getTerms().get(1), equalTo("foobar"));
+        assertThat(response.getTerms().get(2), equalTo("zar"));
+
+        // _terms_enum on mixed clusters (local + remote)
+        req = new TermsEnumRequest("remote_cluster:remote_test", "local_test")
+            .field("foo.keyword");
+        response = client().execute(TermsEnumAction.INSTANCE, req).actionGet();
+        assertTrue(response.isComplete());
+        assertThat(response.getTerms().size(), equalTo(4));
+        assertThat(response.getTerms().get(0), equalTo("bar"));
+        assertThat(response.getTerms().get(1), equalTo("foo"));
+        assertThat(response.getTerms().get(2), equalTo("foobar"));
+        assertThat(response.getTerms().get(3), equalTo("zar"));
+
+        req = new TermsEnumRequest("remote_cluster:remote_test", "local_test")
+            .field("foo.keyword")
+            .searchAfter("foobar");
+        response = client().execute(TermsEnumAction.INSTANCE, req).actionGet();
+        assertTrue(response.isComplete());
+        assertThat(response.getTerms().size(), equalTo(1));
+        assertThat(response.getTerms().get(0), equalTo("zar"));
+
+        req = new TermsEnumRequest("remote_cluster:remote_test", "local_test")
+            .field("foo.keyword")
+            .searchAfter("bar");
+        response = client().execute(TermsEnumAction.INSTANCE, req).actionGet();
+        assertTrue(response.isComplete());
+        assertThat(response.getTerms().size(), equalTo(3));
+        assertThat(response.getTerms().get(0), equalTo("foo"));
+        assertThat(response.getTerms().get(1), equalTo("foobar"));
+        assertThat(response.getTerms().get(2), equalTo("zar"));
+    }
+}

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/termsenum/action/NodeTermsEnumRequest.java

@@ -10,6 +10,7 @@
 import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.core.Nullable;
 import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.transport.TransportRequest;
@@ -20,7 +21,7 @@
 import java.util.Set;
 
 /**
- * Internal terms enum request executed directly against a specific node, querying potentially many 
+ * Internal terms enum request executed directly against a specific node, querying potentially many
  * shards in one request
  */
 public class NodeTermsEnumRequest extends TransportRequest implements IndicesRequest {
@@ -36,12 +37,27 @@ public class NodeTermsEnumRequest extends TransportRequest implements IndicesReq
     private final QueryBuilder indexFilter;
     private Set<ShardId> shardIds;
     private String nodeId;
-
+
+    public NodeTermsEnumRequest(final String nodeId,
+                                final Set<ShardId> shardIds,
+                                TermsEnumRequest request,
+                                long taskStartTimeMillis) {
+        this.field = request.field();
+        this.string = request.string();
+        this.searchAfter = request.searchAfter();
+        this.caseInsensitive = request.caseInsensitive();
+        this.size = request.size();
+        this.timeout = request.timeout().getMillis();
+        this.taskStartedTimeMillis = taskStartTimeMillis;
+        this.indexFilter = request.indexFilter();
+        this.nodeId = nodeId;
+        this.shardIds = shardIds;
+    }
 
     public NodeTermsEnumRequest(StreamInput in) throws IOException {
         super(in);
         field = in.readString();
-        string = in.readString();
+        string = in.readOptionalString();
         searchAfter = in.readOptionalString();
         caseInsensitive = in.readBoolean();
         size = in.readVInt();
@@ -56,36 +72,47 @@ public NodeTermsEnumRequest(StreamInput in) throws IOException {
         }
     }
 
-    public NodeTermsEnumRequest(final String nodeId, final Set<ShardId> shardIds, TermsEnumRequest request) {
-        this.field = request.field();
-        this.string = request.string();
-        this.searchAfter = request.searchAfter();
-        this.caseInsensitive = request.caseInsensitive();
-        this.size = request.size();
-        this.timeout = request.timeout().getMillis();
-        this.taskStartedTimeMillis = request.taskStartTimeMillis;
-        this.indexFilter = request.indexFilter();
-        this.nodeId = nodeId;
-        this.shardIds = shardIds;        
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        super.writeTo(out);
+        out.writeString(field);
+        out.writeOptionalString(string);
+        out.writeOptionalString(searchAfter);
+        out.writeBoolean(caseInsensitive);
+        out.writeVInt(size);
+        // Adjust the amount of permitted time the shard has remaining to gather terms.
+        long timeSpentSoFarInCoordinatingNode = System.currentTimeMillis() - taskStartedTimeMillis;
+        long remainingTimeForShardToUse =  (timeout - timeSpentSoFarInCoordinatingNode);
+        // TODO - if already timed out can we shortcut the trip somehow? Throw exception if remaining time < 0?
+        out.writeVLong(remainingTimeForShardToUse);
+        out.writeVLong(taskStartedTimeMillis);
+        out.writeOptionalNamedWriteable(indexFilter);
+        out.writeString(nodeId);
+        out.writeVInt(shardIds.size());
+        for (ShardId shardId : shardIds) {
+            shardId.writeTo(out);
+        }
     }
 
     public String field() {
         return field;
     }
 
+    @Nullable
     public String string() {
         return string;
     }
 
+    @Nullable
     public String searchAfter() {
         return searchAfter;
     }
 
     public long taskStartedTimeMillis() {
         return this.taskStartedTimeMillis;
     }
-    
-    /** 
+
+    /**
      * The time this request was materialized on a node
      */
     long nodeStartedTimeMillis() {
@@ -94,12 +121,12 @@ long nodeStartedTimeMillis() {
             nodeStartedTimeMillis = System.currentTimeMillis();
         }
         return this.nodeStartedTimeMillis;
-    }    
-    
+    }
+
     public void startTimerOnDataNode() {
         nodeStartedTimeMillis = System.currentTimeMillis();
     }
-    
+
     public Set<ShardId> shardIds() {
         return Collections.unmodifiableSet(shardIds);
     }
@@ -119,28 +146,6 @@ public String nodeId() {
         return nodeId;
     }
 
-    @Override
-    public void writeTo(StreamOutput out) throws IOException {
-        super.writeTo(out);
-        out.writeString(field);
-        out.writeString(string);
-        out.writeOptionalString(searchAfter);
-        out.writeBoolean(caseInsensitive);
-        out.writeVInt(size);
-        // Adjust the amount of permitted time the shard has remaining to gather terms. 
-        long timeSpentSoFarInCoordinatingNode = System.currentTimeMillis() - taskStartedTimeMillis;
-        long remainingTimeForShardToUse =  (timeout - timeSpentSoFarInCoordinatingNode);
-        // TODO - if already timed out can we shortcut the trip somehow? Throw exception if remaining time < 0?
-        out.writeVLong(remainingTimeForShardToUse);
-        out.writeVLong(taskStartedTimeMillis);
-        out.writeOptionalNamedWriteable(indexFilter);
-        out.writeString(nodeId);
-        out.writeVInt(shardIds.size());
-        for (ShardId shardId : shardIds) {
-            shardId.writeTo(out);
-        }
-    }
-
     public QueryBuilder indexFilter() {
         return indexFilter;
     }
@@ -162,5 +167,4 @@ public IndicesOptions indicesOptions() {
     public boolean remove(ShardId shardId) {
         return shardIds.remove(shardId);
     }
-
 }

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/termsenum/action/NodeTermsEnumResponse.java

@@ -41,6 +41,14 @@ class NodeTermsEnumResponse extends TransportResponse {
         this.complete = complete;
     }
 
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeCollection(terms);
+        out.writeOptionalString(error);
+        out.writeBoolean(complete);
+        out.writeString(nodeId);
+    }
+
     public List<TermCount> terms() {
         return this.terms;
     }
@@ -52,17 +60,8 @@ public String getError() {
     public String getNodeId() {
         return nodeId;
     }
-
-    public boolean getComplete() {
-        return complete;
-    }
-
 
-    @Override
-    public void writeTo(StreamOutput out) throws IOException {
-        out.writeCollection(terms);
-        out.writeOptionalString(error);
-        out.writeBoolean(complete);
-        out.writeString(nodeId);
+    public boolean isComplete() {
+        return complete;
     }
 }