/*
 * 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;

/**
 * Provides an interface to an object capable of tracking progress through a collection of elements
 * to be processed.
 *
 * @param <T> the type of elements being tracked
 */
public interface ProgressTracker<T> {
  /**
   * Copies this {@link ProgressTracker}. The copied tracker will maintain its own independent
   * notion of the caller's progress through the collection of elements being processed.
   */
  public ProgressTracker<T> copy();

  /**
   * Reports an element to this {@link ProgressTracker}, as the element is about to be processed.
   */
  public void saw(T element);
}
