Cat API: Add endpoint to show aliases

This endpoint allows to check aliases, their indices, if a filter is
configured along with routing values for searching and indexing.

Closes #4414

src/main/java/org/elasticsearch/rest/action/RestActionModule.java

@@ -220,6 +220,7 @@ public class RestActionModule extends AbstractModule {
         catActionMultibinder.addBinding().to(RestRecoveryAction.class).asEagerSingleton();
         catActionMultibinder.addBinding().to(RestHealthAction.class).asEagerSingleton();
         catActionMultibinder.addBinding().to(org.elasticsearch.rest.action.cat.RestPendingClusterTasksAction.class).asEagerSingleton();
+        catActionMultibinder.addBinding().to(RestAliasAction.class).asEagerSingleton();
         // no abstract cat action
         bind(RestCatAction.class).asEagerSingleton();
     }

src/main/java/org/elasticsearch/rest/action/cat/RestAliasAction.java

@@ -0,0 +1,132 @@
+/*
+ * Licensed to ElasticSearch and Shay Banon 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.rest.action.cat;
+
+import com.carrotsearch.hppc.cursors.ObjectObjectCursor;
+import org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.admin.cluster.state.ClusterStateRequest;
+import org.elasticsearch.action.admin.cluster.state.ClusterStateResponse;
+import org.elasticsearch.client.Client;
+import org.elasticsearch.cluster.metadata.AliasMetaData;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.Table;
+import org.elasticsearch.common.collect.ImmutableOpenMap;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.rest.RestChannel;
+import org.elasticsearch.rest.RestController;
+import org.elasticsearch.rest.RestRequest;
+import org.elasticsearch.rest.XContentThrowableRestResponse;
+import org.elasticsearch.rest.action.support.RestTable;
+
+import java.io.IOException;
+import java.util.Iterator;
+
+import static org.elasticsearch.rest.RestRequest.Method.GET;
+
+/**
+ *
+ */
+public class RestAliasAction extends AbstractCatAction {
+
+    @Inject
+    public RestAliasAction(Settings settings, Client client, RestController controller) {
+        super(settings, client);
+        controller.registerHandler(GET, "/_cat/aliases", this);
+        controller.registerHandler(GET, "/_cat/aliases/{alias}", this);
+    }
+
+
+    @Override
+    void doRequest(final RestRequest request, final RestChannel channel) {
+        final ClusterStateRequest clusterStateRequest = new ClusterStateRequest();
+        clusterStateRequest.filterMetaData(true);
+        clusterStateRequest.local(request.paramAsBoolean("local", clusterStateRequest.local()));
+        clusterStateRequest.masterNodeTimeout(request.paramAsTime("master_timeout", clusterStateRequest.masterNodeTimeout()));
+        clusterStateRequest.filterAll().filterMetaData(false);
+
+        client.admin().cluster().state(clusterStateRequest, new ActionListener<ClusterStateResponse>() {
+
+            @Override
+            public void onResponse(ClusterStateResponse response) {
+                try {
+                    Table tab = buildTable(request, response);
+                    channel.sendResponse(RestTable.buildResponse(tab, request, channel));
+                } catch (Throwable e) {
+                    onFailure(e);
+                }
+            }
+
+            @Override
+            public void onFailure(Throwable e) {
+                try {
+                    channel.sendResponse(new XContentThrowableRestResponse(request, e));
+                } catch (IOException e1) {
+                    logger.error("Failed to send failure response", e1);
+                }
+            }
+        });
+    }
+
+    @Override
+    void documentation(StringBuilder sb) {
+        sb.append("/_cat_alias");
+        sb.append("/_cat_alias/{alias}");
+    }
+
+    @Override
+    Table getTableWithHeader(RestRequest request) {
+        final Table table = new Table();
+        table.startHeaders();
+        table.addCell("alias", "desc:alias name");
+        table.addCell("index", "desc:index alias points to");
+        table.addCell("filter", "desc:filter");
+        table.addCell("index_routing", "desc:index routing");
+        table.addCell("search_routing", "desc:search routing");
+        table.endHeaders();
+        return table;
+    }
+
+    private Table buildTable(RestRequest request, ClusterStateResponse response) {
+        Table table = getTableWithHeader(request);
+
+        for (ObjectObjectCursor<String, ImmutableOpenMap<String, AliasMetaData>> cursor : response.getState().getMetaData().aliases()) {
+            String aliasName = cursor.key;
+            Iterator<ObjectObjectCursor<String,AliasMetaData>> iterator = cursor.value.iterator();
+            while (iterator.hasNext()) {
+                ObjectObjectCursor<String, AliasMetaData> iteratorCursor = iterator.next();
+                String indexName = iteratorCursor.key;
+                AliasMetaData aliasMetaData = iteratorCursor.value;
+
+                table.startRow();
+                table.addCell(aliasName);
+                table.addCell(indexName);
+                table.addCell(aliasMetaData.filteringRequired() ? "*" : "-");
+                String indexRouting = Strings.hasLength(aliasMetaData.indexRouting()) ? aliasMetaData.indexRouting() : "-";
+                table.addCell(indexRouting);
+                String searchRouting = Strings.hasLength(aliasMetaData.searchRouting()) ? aliasMetaData.searchRouting() : "-";
+                table.addCell(searchRouting);
+                table.endRow();
+            }
+        }
+
+        return table;
+    }
+
+}