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   * distributed with this work for additional information
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   * 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
   *
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  package org.apache.beam.sdk.nexmark.queries;
  
  import org.apache.beam.sdk.nexmark.Monitor;
  import org.apache.beam.sdk.nexmark.NexmarkConfiguration;
  import org.apache.beam.sdk.nexmark.NexmarkUtils;
  import org.apache.beam.sdk.nexmark.model.Event;
  import org.apache.beam.sdk.nexmark.model.KnownSize;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.TimestampedValue;
  
  /** Wrapper for 'NEXmark' query transforms that adds monitoring and snooping. */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public final class NexmarkQuery<T extends KnownSize>
      extends PTransform<PCollection<Event>, PCollection<? extends TimestampedValue<T>>> {
  
    final NexmarkConfiguration configuration;
    public final Monitor<Event> eventMonitor;
    public final Monitor<T> resultMonitor;
    private final NexmarkQueryTransform<T> transform;
  
    public NexmarkQuery(NexmarkConfiguration configuration, NexmarkQueryTransform<T> transform) {
      super(transform.getName());
      this.configuration = configuration;
      this.transform = transform;
      if (configuration.debug) {
        eventMonitor = new Monitor<>(name + ".Events", "event");
        resultMonitor = new Monitor<>(name + ".Results", "result");
      } else {
        eventMonitor = null;
        resultMonitor = null;
      }
    }
  
    public NexmarkQueryTransform<T> getTransform() {
      return transform;
    }
  
    @Override
    public PCollection<TimestampedValue<T>> expand(PCollection<Event> events) {
  
      if (configuration.debug) {
        events =
            events
                // Monitor events as they go by.
                .apply(name + ".Monitor", eventMonitor.getTransform())
                // Count each type of event.
                .apply(name + ".Snoop", NexmarkUtils.snoop(name));
      }
  
      if (configuration.cpuDelayMs > 0) {
        // Slow down by pegging one core at 100%.
        events =
            events.apply(name + ".CpuDelay", NexmarkUtils.cpuDelay(name, configuration.cpuDelayMs));
      }
  
      if (configuration.diskBusyBytes > 0) {
        // Slow down by forcing bytes to durable store.
        events = events.apply(name + ".DiskBusy", NexmarkUtils.diskBusy(configuration.diskBusyBytes));
      }
  
      // Run the query.
      PCollection<T> queryResults = events.apply(transform);
  
      if (configuration.debug) {
        // Monitor results as they go by.
        queryResults = queryResults.apply(name + ".Debug", resultMonitor.getTransform());
      }
  
      // Timestamp the query results.
      return queryResults.apply(name + ".Stamp", NexmarkUtils.stamp(name));
    }
  }
  