Add _cat/health.

% curl localhost:9200/_cat/health\?v=1\&ts=0
cluster  status nodeTotal nodeData shards pri relo init unassign
kluster green          1        1     20  20    0    0        0

% curl localhost:9200/_cat/health\?ts=0
kluster green 1 1 20 20 0 0 0

% curl localhost:9200/_cat/health\?v=1
epoch      time     cluster  status nodeTotal nodeData shards pri relo init unassign
1383341092 16:24:52 kluster green          1        1     20  20    0    0        0

% curl localhost:9200/_cat/health
1383341119 16:25:19 kluster green 1 1 20 20 0 0 0

Closes #4050.

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

@@ -70,12 +70,7 @@ import org.elasticsearch.rest.action.admin.indices.warmer.delete.RestDeleteWarme
 import org.elasticsearch.rest.action.admin.indices.warmer.get.RestGetWarmerAction;
 import org.elasticsearch.rest.action.admin.indices.warmer.put.RestPutWarmerAction;
 import org.elasticsearch.rest.action.bulk.RestBulkAction;
-import org.elasticsearch.rest.action.cat.RestAllocationAction;
-import org.elasticsearch.rest.action.cat.RestShardsAction;
-import org.elasticsearch.rest.action.cat.RestIndicesAction;
-import org.elasticsearch.rest.action.cat.RestMasterAction;
-import org.elasticsearch.rest.action.cat.RestNodesAction;
-import org.elasticsearch.rest.action.cat.RestRecoveryAction;
+import org.elasticsearch.rest.action.cat.*;
 import org.elasticsearch.rest.action.delete.RestDeleteAction;
 import org.elasticsearch.rest.action.deletebyquery.RestDeleteByQueryAction;
 import org.elasticsearch.rest.action.explain.RestExplainAction;
@@ -189,6 +184,7 @@ public class RestActionModule extends AbstractModule {
 
         bind(RestSearchAction.class).asEagerSingleton();
         bind(RestSearchScrollAction.class).asEagerSingleton();
+        bind(RestClearScrollAction.class).asEagerSingleton();
         bind(RestMultiSearchAction.class).asEagerSingleton();
 
         bind(RestValidateQueryAction.class).asEagerSingleton();
@@ -205,6 +201,6 @@ public class RestActionModule extends AbstractModule {
         // Fully qualified to prevent interference with rest.action.count.RestCountAction
         bind(org.elasticsearch.rest.action.cat.RestCountAction.class).asEagerSingleton();
         bind(RestRecoveryAction.class).asEagerSingleton();
-        bind(RestClearScrollAction.class).asEagerSingleton();
+        bind(RestHealthAction.class).asEagerSingleton();
     }
 }

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

@@ -0,0 +1,108 @@
+/*
+ * 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 org.elasticsearch.action.ActionListener;
+import org.elasticsearch.action.admin.cluster.health.ClusterHealthRequest;
+import org.elasticsearch.action.admin.cluster.health.ClusterHealthResponse;
+import org.elasticsearch.client.Client;
+import org.elasticsearch.common.Table;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.table.TimestampedTable;
+import org.elasticsearch.rest.*;
+import org.elasticsearch.rest.action.support.RestTable;
+
+import java.io.IOException;
+import java.util.Locale;
+
+import static org.elasticsearch.rest.RestRequest.Method.GET;
+
+public class RestHealthAction extends BaseRestHandler {
+
+    @Inject
+    public RestHealthAction(Settings settings, Client client, RestController controller) {
+        super(settings, client);
+        controller.registerHandler(GET, "/_cat/health", this);
+    }
+
+    @Override
+    public void handleRequest(final RestRequest request, final RestChannel channel) {
+        ClusterHealthRequest clusterHealthRequest = new ClusterHealthRequest();
+        final boolean timeStamp = request.paramAsBoolean("ts", true);
+
+        client.admin().cluster().health(clusterHealthRequest, new ActionListener<ClusterHealthResponse>() {
+            @Override
+            public void onResponse(final ClusterHealthResponse health) {
+                try {
+                    channel.sendResponse(RestTable.buildResponse(buildTable(health, timeStamp), request, channel));
+                } catch (Throwable t) {
+                    onFailure(t);
+                }
+            }
+
+            @Override
+            public void onFailure(Throwable e) {
+                try {
+                    channel.sendResponse(new XContentThrowableRestResponse(request, e));
+                } catch (IOException e1) {
+                    logger.error("Failed to send failure response", e1);
+                }
+            }
+        });
+    }
+
+    private Table buildTable (final ClusterHealthResponse health, boolean timeStamp) {
+        Table t;
+
+        if (timeStamp) {
+            t = new TimestampedTable();
+        } else {
+            t = new Table();
+        }
+
+        if (null != health) {
+            t.startHeaders();
+            t.addCell("cluster");
+            t.addCell("status");
+            t.addCell("nodeTotal", "text-align:right;");
+            t.addCell("nodeData", "text-align:right;");
+            t.addCell("shards", "text-align:right;");
+            t.addCell("pri", "text-align:right;");
+            t.addCell("relo", "text-align:right;");
+            t.addCell("init", "text-align:right;");
+            t.addCell("unassign", "text-align:right;");
+            t.endHeaders();
+
+            t.startRow();
+            t.addCell(health.getClusterName());
+            t.addCell(health.getStatus().name().toLowerCase(Locale.ROOT));
+            t.addCell(health.getNumberOfNodes());
+            t.addCell(health.getNumberOfDataNodes());
+            t.addCell(health.getActiveShards());
+            t.addCell(health.getActivePrimaryShards());
+            t.addCell(health.getRelocatingShards());
+            t.addCell(health.getInitializingShards());
+            t.addCell(health.getUnassignedShards());
+            t.endRow();
+        }
+        return t;
+    }
+}