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.common.grpc.stats;
  
  import io.grpc.CallOptions;
  import io.grpc.Channel;
  import io.grpc.ClientCall;
  import io.grpc.ClientInterceptor;
  import io.grpc.MethodDescriptor;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import org.apache.bookkeeper.common.grpc.stats.ClientStats.Factory;
  import org.apache.bookkeeper.stats.StatsLogger;
  
  /**
   * A {@link ClientInterceptor} that sends stats about grpc calls to stats logger.
   */
  public class MonitoringClientInterceptor implements ClientInterceptor {
  
      /**
       * Create a monitoring client interceptor with provided stats logger and configuration.
       *
       * @param statsLogger stats logger to collect grpc stats
       * @param includeLatencyHistograms flag indicates whether to include latency histograms or not
       * @return a monitoring client interceptor
       */
      public static MonitoringClientInterceptor create(StatsLogger statsLogger,
                                                       boolean includeLatencyHistograms) {
          return new MonitoringClientInterceptor(
              new Factory(includeLatencyHistograms), statsLogger);
      }
  
      private final Factory statsFactory;
      private final StatsLogger statsLogger;
      private final ConcurrentMap<String, ClientStats> methods;
  
      private MonitoringClientInterceptor(Factory statsFactory,
                                          StatsLogger statsLogger) {
          this.statsFactory = statsFactory;
          this.statsLogger = statsLogger;
          this.methods = new ConcurrentHashMap<>();
      }
  
      private ClientStats getMethodStats(MethodDescriptor<?, ?> method) {
          ClientStats stats = methods.get(method.getFullMethodName());
          if (null != stats) {
              return stats;
          }
          ClientStats newStats = statsFactory.createMetricsForMethod(method, statsLogger);
          ClientStats oldStats = methods.putIfAbsent(method.getFullMethodName(), newStats);
          if (null != oldStats) {
              return oldStats;
          } else {
              return newStats;
          }
      }
  
      @Override
      public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
          MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
          ClientStats stats = getMethodStats(method);
          return new MonitoringClientCall<>(
              next.newCall(method, callOptions),
              stats
          );
      }
  }
  