content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.apache.bookkeeper.server.http.service;
  
  import java.io.IOException;
  import java.io.StringWriter;
  import org.apache.bookkeeper.conf.ServerConfiguration;
  import org.apache.bookkeeper.http.HttpServer.Method;
  import org.apache.bookkeeper.http.HttpServer.StatusCode;
  import org.apache.bookkeeper.http.service.HttpEndpointService;
  import org.apache.bookkeeper.http.service.HttpServiceRequest;
  import org.apache.bookkeeper.http.service.HttpServiceResponse;
  import org.apache.bookkeeper.stats.StatsProvider;
  
  /**
   * HttpEndpointService that handle exposing metrics.
   *
   * <p>The GET method will return all the emtrics collected at stats provider.
   */
  public class MetricsService implements HttpEndpointService {
  
      public static final String PROMETHEUS_CONTENT_TYPE_004 = "text/plain; version=0.0.4; charset=utf-8";
  
      private final ServerConfiguration conf;
      private final StatsProvider statsProvider;
  
      public MetricsService(ServerConfiguration conf,
                            StatsProvider statsProvider) {
          this.conf = conf;
          this.statsProvider = statsProvider;
      }
  
      @Override
      public HttpServiceResponse handle(HttpServiceRequest request) throws Exception {
          HttpServiceResponse response = new HttpServiceResponse();
          if (Method.GET != request.getMethod()) {
              response.setCode(StatusCode.FORBIDDEN);
              response.setBody(request.getMethod() + " is forbidden. Should be GET method");
              return response;
          }
  
          if (null == statsProvider) {
              response.setCode(StatusCode.INTERNAL_ERROR);
              response.setBody("Stats provider is not enabled. Please enable it by set statsProviderClass"
                  + " on bookie configuration");
              return response;
          }
  
          // GET
          try (StringWriter writer = new StringWriter(1024)) {
              statsProvider.writeAllMetrics(writer);
              writer.flush();
              response.setCode(StatusCode.OK);
              response.setContentType(PROMETHEUS_CONTENT_TYPE_004);
              response.setBody(writer.getBuffer().toString());
          } catch (UnsupportedOperationException uoe) {
              response.setCode(StatusCode.INTERNAL_ERROR);
              response.setBody("Currently stats provider doesn't support exporting metrics in http service");
          } catch (IOException ioe) {
              response.setCode(StatusCode.INTERNAL_ERROR);
              response.setBody("Exceptions are thrown when exporting metrics : " + ioe.getMessage());
          }
          return response;
      }
  }
  