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.spark.structuredstreaming.metrics;
  
  import org.apache.beam.runners.core.metrics.MetricsContainerStepMap;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.annotations.VisibleForTesting;
  import org.apache.spark.sql.SparkSession;
  import org.apache.spark.util.AccumulatorV2;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * {@link AccumulatorV2} for Beam metrics captured in {@link MetricsContainerStepMap}.
   *
   * @see <a
   *     href="https://spark.apache.org/docs/latest/streaming-programming-guide.html#accumulators-broadcast-variables-and-checkpoints">accumulatorsV2</a>
   */
  public class MetricsAccumulator
      extends AccumulatorV2<MetricsContainerStepMap, MetricsContainerStepMap> {
    private static final Logger LOG = LoggerFactory.getLogger(MetricsAccumulator.class);
    private static final MetricsContainerStepMap EMPTY = new SparkMetricsContainerStepMap();
    private static final String ACCUMULATOR_NAME = "Beam.Metrics";
  
    private static volatile @Nullable MetricsAccumulator instance = null;
  
    private MetricsContainerStepMap value;
  
    public MetricsAccumulator() {
      value = new SparkMetricsContainerStepMap();
    }
  
    private MetricsAccumulator(MetricsContainerStepMap value) {
      this.value = value;
    }
  
    @Override
    public boolean isZero() {
      return value.equals(EMPTY);
    }
  
    @Override
    public MetricsAccumulator copy() {
      MetricsContainerStepMap newContainer = new SparkMetricsContainerStepMap();
      newContainer.updateAll(value);
      return new MetricsAccumulator(newContainer);
    }
  
    @Override
    public void reset() {
      value = new SparkMetricsContainerStepMap();
    }
  
    @Override
    public void add(MetricsContainerStepMap other) {
      value.updateAll(other);
    }
  
    @Override
    public void merge(AccumulatorV2<MetricsContainerStepMap, MetricsContainerStepMap> other) {
      value.updateAll(other.value());
    }
  
    @Override
    public MetricsContainerStepMap value() {
      return value;
    }
  
    /**
     * Get the {@link MetricsAccumulator} on this driver. If there's no such accumulator yet, it will
     * be created and registered using the provided {@link SparkSession}.
     */
    public static MetricsAccumulator getInstance(SparkSession session) {
      MetricsAccumulator current = instance;
      if (current != null) {
        return current;
      }
      synchronized (MetricsAccumulator.class) {
        MetricsAccumulator accumulator = instance;
        if (accumulator == null) {
          accumulator = new MetricsAccumulator();
          session.sparkContext().register(accumulator, ACCUMULATOR_NAME);
          instance = accumulator;
          LOG.info("Instantiated metrics accumulator: {}", instance.value());
        }
        return accumulator;
      }
    }
  
    @VisibleForTesting
    public static void clear() {
      synchronized (MetricsAccumulator.class) {
        instance = null;
      }
    }
  
    /**
     * Sole purpose of this class is to override {@link #toString()} of {@link
     * MetricsContainerStepMap} in order to show meaningful metrics in Spark Web Interface.
     */
    private static class SparkMetricsContainerStepMap extends MetricsContainerStepMap {
  
      @Override
      public String toString() {
        return asAttemptedOnlyMetricResults(this).toString();
      }
  
      @Override
      public boolean equals(@Nullable Object o) {
        return super.equals(o);
      }
  
      @Override
      public int hashCode() {
        return super.hashCode();
      }
    }
  }
  