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.cassandra.metrics;
  
  import java.time.Duration;
  import java.util.concurrent.Callable;
  import java.util.concurrent.TimeUnit;
  import java.util.function.Supplier;
  
  import com.codahale.metrics.Metered;
  import com.codahale.metrics.Sampling;
  
  /**
   * An interface which mimics {@link com.codahale.metrics.Timer} API and allows alternative implementations
   */
  public interface Timer extends Metered, Sampling
  {
      /**
       * A timing context.
       */
      class Context implements AutoCloseable
      {
          private final Timer timer;
          private final MetricClock clock;
          private final long startTime;
  
          Context(Timer timer, MetricClock clock)
          {
              this.timer = timer;
              this.clock = clock;
              this.startTime = clock.getTick();
          }
  
          /**
           * Updates the timer with the difference between current and start time. Call to this method will
           * not reset the start time. Multiple calls result in multiple updates.
           *
           * @return the elapsed time in nanoseconds
           */
          public long stop()
          {
              final long elapsed = clock.getTick() - startTime;
              timer.update(elapsed, clock.getTickUnit());
              return elapsed;
          }
  
          /**
           * Equivalent to calling {@link #stop()}.
           */
          @Override
          public void close()
          {
              stop();
          }
      }
  
      void update(long duration, TimeUnit unit);
  
      void update(Duration duration);
  
      <T> T time(Callable<T> event) throws Exception;
  
      <T> T timeSupplier(Supplier<T> event);
  
      void time(Runnable event);
  
      /* we have to implement another method instead of time() due to 2 reasons:
       * 1) com.codahale.metrics.Timer.Context cannot be inhereted - it has only a package-private constructor
       * 2) we want to avoid direct dependency to com.codahale.metrics.Timer.Context in other Cassandra classes
       */
      Context startTime();
  }
  