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.beam.runners.dataflow.worker.util.common.worker;
  
  import org.apache.beam.runners.dataflow.worker.counters.CounterName;
  import org.apache.beam.runners.dataflow.worker.counters.NameContext;
  
  /** Tracks per-element execution time of a single execution thread. */
  public abstract class ElementExecutionTracker {
    public static final ElementExecutionTracker NO_OP_INSTANCE = new NoopElementTracker();
    public static final CounterName COUNTER_NAME = CounterName.named("per-element-processing-time");
  
    /**
     * Indicates that the execution thread has entered the process method for a new input element in
     * the specified step.
     */
    public abstract void enter(NameContext step);
  
    /** Indicates that the execution thread has returned from process method. */
    public abstract void exit();
  
    /** Attribute processing time to executing elements since the last sampling period. */
    public abstract void takeSample(long millisSinceLastSample);
  
    /** Retrieve a no-op {@link ElementExecutionTracker} instance for testing. */
    public static ElementExecutionTracker newForTest() {
      return NO_OP_INSTANCE;
    }
  
    /** No-op implementation to stub in when functionality is disabled. */
    private static final class NoopElementTracker extends ElementExecutionTracker {
      @Override
      public void takeSample(long millisSinceLastSample) {}
  
      @Override
      public void enter(NameContext step) {}
  
      @Override
      public void exit() {}
    }
  }
  