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.core.metrics;
  
  import java.util.Objects;
  import java.util.concurrent.atomic.AtomicReference;
  import org.apache.beam.sdk.metrics.Gauge;
  import org.apache.beam.sdk.metrics.MetricName;
  import org.apache.beam.sdk.metrics.MetricsContainer;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Tracks the current value (and delta) for a {@link Gauge} metric.
   *
   * <p>This class generally shouldn't be used directly. The only exception is within a runner where a
   * gauge is being reported for a specific step (rather than the gauge in the current context). In
   * that case retrieving the underlying cell and reporting directly to it avoids a step of
   * indirection.
   */
  public class GaugeCell implements Gauge, MetricCell<GaugeData> {
  
    private final DirtyState dirty = new DirtyState();
    private final AtomicReference<GaugeData> gaugeValue = new AtomicReference<>(GaugeData.empty());
    private final MetricName name;
  
    /**
     * Generally, runners should construct instances using the methods in {@link
     * MetricsContainerImpl}, unless they need to define their own version of {@link
     * MetricsContainer}. These constructors are *only* public so runners can instantiate.
     */
    public GaugeCell(MetricName name) {
      this.name = name;
    }
  
    @Override
    public void reset() {
      gaugeValue.set(GaugeData.empty());
      dirty.reset();
    }
  
    /** Set the gauge to the given value. */
    @Override
    public void set(long value) {
      update(GaugeData.create(value));
    }
  
    void update(GaugeData data) {
      GaugeData original;
      do {
        original = gaugeValue.get();
      } while (!gaugeValue.compareAndSet(original, original.combine(data)));
      dirty.afterModification();
    }
  
    @Override
    public DirtyState getDirty() {
      return dirty;
    }
  
    @Override
    public GaugeData getCumulative() {
      return gaugeValue.get();
    }
  
    @Override
    public MetricName getName() {
      return name;
    }
  
    @Override
    public boolean equals(@Nullable Object object) {
      if (object instanceof GaugeCell) {
        GaugeCell gaugeCell = (GaugeCell) object;
        return Objects.equals(dirty, gaugeCell.dirty)
            && Objects.equals(gaugeValue.get(), gaugeCell.gaugeValue.get())
            && Objects.equals(name, gaugeCell.name);
      }
  
      return false;
    }
  
    @Override
    public int hashCode() {
      return Objects.hash(dirty, gaugeValue.get(), name);
    }
  }
  