Fix template HEAD requests

Template HEAD requests incorrectly return a content-length header of
0. This commit addresses this by removing the special handling for
template HEAD requests, and just relying on the general mechanism that
exists for handling HEAD requests in the REST layer.

Relates #23130

core/src/main/java/org/elasticsearch/action/ActionModule.java

@@ -248,7 +248,6 @@ import org.elasticsearch.rest.action.admin.indices.RestGetIndexTemplateAction;
 import org.elasticsearch.rest.action.admin.indices.RestGetIndicesAction;
 import org.elasticsearch.rest.action.admin.indices.RestGetMappingAction;
 import org.elasticsearch.rest.action.admin.indices.RestGetSettingsAction;
-import org.elasticsearch.rest.action.admin.indices.RestHeadIndexTemplateAction;
 import org.elasticsearch.rest.action.admin.indices.RestIndexDeleteAliasesAction;
 import org.elasticsearch.rest.action.admin.indices.RestIndexPutAliasAction;
 import org.elasticsearch.rest.action.admin.indices.RestIndicesAliasesAction;
@@ -549,7 +548,6 @@ public class ActionModule extends AbstractModule {
         registerHandler.accept(new RestGetIndexTemplateAction(settings, restController));
         registerHandler.accept(new RestPutIndexTemplateAction(settings, restController));
         registerHandler.accept(new RestDeleteIndexTemplateAction(settings, restController));
-        registerHandler.accept(new RestHeadIndexTemplateAction(settings, restController));
 
         registerHandler.accept(new RestPutMappingAction(settings, restController));
         registerHandler.accept(new RestGetMappingAction(settings, restController));

core/src/main/java/org/elasticsearch/rest/action/admin/indices/RestGetIndexTemplateAction.java

@@ -34,22 +34,27 @@ import java.io.IOException;
 import java.util.Set;
 
 import static org.elasticsearch.rest.RestRequest.Method.GET;
+import static org.elasticsearch.rest.RestRequest.Method.HEAD;
 import static org.elasticsearch.rest.RestStatus.NOT_FOUND;
 import static org.elasticsearch.rest.RestStatus.OK;
 
+/**
+ * The REST handler for get template and head template APIs.
+ */
 public class RestGetIndexTemplateAction extends BaseRestHandler {
-    public RestGetIndexTemplateAction(Settings settings, RestController controller) {
-        super(settings);
 
+    public RestGetIndexTemplateAction(final Settings settings, final RestController controller) {
+        super(settings);
         controller.registerHandler(GET, "/_template", this);
         controller.registerHandler(GET, "/_template/{name}", this);
+        controller.registerHandler(HEAD, "/_template/{name}", this);
     }
 
     @Override
     public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
         final String[] names = Strings.splitStringByCommaToArray(request.param("name"));
 
-        GetIndexTemplatesRequest getIndexTemplatesRequest = new GetIndexTemplatesRequest(names);
+        final GetIndexTemplatesRequest getIndexTemplatesRequest = new GetIndexTemplatesRequest(names);
         getIndexTemplatesRequest.local(request.paramAsBoolean("local", getIndexTemplatesRequest.local()));
         getIndexTemplatesRequest.masterNodeTimeout(request.paramAsTime("master_timeout", getIndexTemplatesRequest.masterNodeTimeout()));
 
@@ -60,9 +65,8 @@ public class RestGetIndexTemplateAction extends BaseRestHandler {
                         .indices()
                         .getTemplates(getIndexTemplatesRequest, new RestToXContentListener<GetIndexTemplatesResponse>(channel) {
                             @Override
-                            protected RestStatus getStatus(GetIndexTemplatesResponse response) {
+                            protected RestStatus getStatus(final GetIndexTemplatesResponse response) {
-                                boolean templateExists = false == response.getIndexTemplates().isEmpty();
+                                final boolean templateExists = response.getIndexTemplates().isEmpty() == false;
-
                                 return (templateExists || implicitAll) ? OK : NOT_FOUND;
                             }
                         });

core/src/main/java/org/elasticsearch/rest/action/admin/indices/RestHeadIndexTemplateAction.java

@@ -1,73 +0,0 @@
-/*
- * 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.rest.action.admin.indices;
-
-import org.elasticsearch.action.admin.indices.template.get.GetIndexTemplatesRequest;
-import org.elasticsearch.action.admin.indices.template.get.GetIndexTemplatesResponse;
-import org.elasticsearch.client.node.NodeClient;
-import org.elasticsearch.common.bytes.BytesArray;
-import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.rest.BaseRestHandler;
-import org.elasticsearch.rest.BytesRestResponse;
-import org.elasticsearch.rest.RestController;
-import org.elasticsearch.rest.RestRequest;
-import org.elasticsearch.rest.RestResponse;
-import org.elasticsearch.rest.action.RestResponseListener;
-
-import java.io.IOException;
-import java.util.Set;
-
-import static org.elasticsearch.rest.RestRequest.Method.HEAD;
-import static org.elasticsearch.rest.RestStatus.NOT_FOUND;
-import static org.elasticsearch.rest.RestStatus.OK;
-
-public class RestHeadIndexTemplateAction extends BaseRestHandler {
-    public RestHeadIndexTemplateAction(Settings settings, RestController controller) {
-        super(settings);
-
-        controller.registerHandler(HEAD, "/_template/{name}", this);
-    }
-
-    @Override
-    public RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {
-        GetIndexTemplatesRequest getIndexTemplatesRequest = new GetIndexTemplatesRequest(request.param("name"));
-        getIndexTemplatesRequest.local(request.paramAsBoolean("local", getIndexTemplatesRequest.local()));
-        getIndexTemplatesRequest.masterNodeTimeout(request.paramAsTime("master_timeout", getIndexTemplatesRequest.masterNodeTimeout()));
-        return channel ->
-                client.admin()
-                        .indices()
-                        .getTemplates(getIndexTemplatesRequest, new RestResponseListener<GetIndexTemplatesResponse>(channel) {
-                            @Override
-                            public RestResponse buildResponse(GetIndexTemplatesResponse getIndexTemplatesResponse) {
-                                boolean templateExists = getIndexTemplatesResponse.getIndexTemplates().size() > 0;
-                                if (templateExists) {
-                                    return new BytesRestResponse(OK, BytesRestResponse.TEXT_CONTENT_TYPE, BytesArray.EMPTY);
-                                } else {
-                                    return new BytesRestResponse(NOT_FOUND, BytesRestResponse.TEXT_CONTENT_TYPE, BytesArray.EMPTY);
-                                }
-                            }
-                        });
-    }
-
-    @Override
-    protected Set<String> responseParams() {
-        return Settings.FORMAT_PARAMS;
-    }
-
-}

modules/transport-netty4/src/test/java/org/elasticsearch/rest/Netty4HeadBodyIsEmptyIT.java

@@ -92,6 +92,24 @@ public class Netty4HeadBodyIsEmptyIT extends ESRestTestCase {
         }
     }
 
+    public void testTemplateExists() throws IOException {
+        try (XContentBuilder builder = jsonBuilder()) {
+            builder.startObject();
+            {
+                builder.array("index_patterns", "*");
+                builder.startObject("settings");
+                {
+                    builder.field("number_of_replicas", 0);
+                }
+                builder.endObject();
+            }
+            builder.endObject();
+
+            client().performRequest("PUT", "/_template/template", emptyMap(), new StringEntity(builder.string()));
+            headTestCase("/_template/template", emptyMap(), greaterThan(0));
+        }
+    }
+
     private void headTestCase(String url, Map<String, String> params, Matcher<Integer> matcher) throws IOException {
         Response response = client().performRequest("HEAD", url, params);
         assertEquals(200, response.getStatusLine().getStatusCode());