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;
  
  import com.google.api.client.util.Clock;
  import org.apache.beam.runners.dataflow.util.TimeUtil;
  import org.joda.time.Duration;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class HotKeyLogger {
    private final Logger LOG = LoggerFactory.getLogger(HotKeyLogger.class);
  
    /** Clock used to either provide real system time or mocked to virtualize time for testing. */
    private Clock clock = Clock.SYSTEM;
  
    /**
     * The previous time the HotKeyDetection was logged. This is used to throttle logging to every 5
     * minutes.
     */
    private long prevHotKeyDetectionLogMs = 0;
  
    /** Throttles logging the detection to every loggingPeriod */
    private final Duration loggingPeriod = Duration.standardMinutes(5);
  
    HotKeyLogger() {}
  
    HotKeyLogger(Clock clock) {
      this.clock = clock;
    }
  
    /** Logs a detection of the hot key every 5 minutes. */
    public void logHotKeyDetection(String userStepName, Duration hotKeyAge) {
      if (isThrottled()) {
        return;
      }
      LOG.warn(
          "A hot key was detected in step '{}' with age of '{}'. This is "
              + "a symptom of key distribution being skewed. To fix, please inspect your data and "
              + "pipeline to ensure that elements are evenly distributed across your key space. If "
              + "you want to log the plain-text key to Cloud Logging please re-run with the "
              + "`hotKeyLoggingEnabled` pipeline option. See "
              + "https://cloud.google.com/dataflow/docs/guides/specifying-exec-params for more "
              + "information.",
          userStepName,
          TimeUtil.toCloudDuration(hotKeyAge));
    }
  
    /** Logs a detection of the hot key every 5 minutes with the given key. */
    public void logHotKeyDetection(String userStepName, Duration hotKeyAge, Object hotkey) {
      if (isThrottled()) {
        return;
      }
  
      LOG.warn(
          "A hot key '{}' was detected in step '{}' with age of '{}'. This is "
              + "a symptom of key distribution being skewed. To fix, please inspect your data and "
              + "pipeline to ensure that elements are evenly distributed across your key space.",
          hotkey,
          userStepName,
          TimeUtil.toCloudDuration(hotKeyAge));
    }
  
    /**
     * Returns true if the class should log the HotKeyMessage. This method throttles logging to every
     * 5 minutes.
     */
    protected boolean isThrottled() {
      // Throttle logging the HotKeyDetection to every 5 minutes.
      long nowMs = clock.currentTimeMillis();
      if (nowMs - prevHotKeyDetectionLogMs < loggingPeriod.getMillis()) {
        return true;
      }
      prevHotKeyDetectionLogMs = nowMs;
      return false;
    }
  }
  