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.asterix.transaction.management.service.recovery;
  
  import org.apache.asterix.common.transactions.ICheckpointManager;
  import org.apache.asterix.common.transactions.ILogManager;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  /**
   * A daemon thread that periodically attempts to perform checkpoints.
   * A checkpoint attempt is made when the volume of transaction logs written
   * since the last successful checkpoint exceeds a certain threshold.
   */
  public class CheckpointThread extends Thread {
  
      private static final Logger LOGGER = LogManager.getLogger();
      private long lsnThreshold;
      private long checkpointTermInSecs;
  
      private final ILogManager logManager;
      private final ICheckpointManager checkpointManager;
      private volatile boolean shouldRun = true;
  
      public CheckpointThread(ICheckpointManager checkpointManager, ILogManager logManager, long lsnThreshold,
              long checkpointTermInSecs) {
          this.checkpointManager = checkpointManager;
          this.logManager = logManager;
          this.lsnThreshold = lsnThreshold;
          this.checkpointTermInSecs = checkpointTermInSecs;
          setDaemon(true);
      }
  
      @Override
      public void run() {
          Thread.currentThread().setName("Checkpoint Thread (" + Thread.currentThread().getId() + ")");
          long currentCheckpointAttemptMinLSN;
          long lastCheckpointLSN = -1;
          long currentLogLSN;
          long targetCheckpointLSN;
          while (shouldRun) {
              try {
                  sleep(checkpointTermInSecs * 1000);
                  if (!shouldRun) {
                      return;
                  }
                  if (lastCheckpointLSN == -1) {
                      //Since the system just started up after sharp checkpoint,
                      //last checkpoint LSN is considered as the min LSN of the current log partition
                      lastCheckpointLSN = logManager.getReadableSmallestLSN();
                  }
                  checkpointManager.checkpointIdleDatasets();
  
                  //1. get current log LSN
                  currentLogLSN = logManager.getAppendLSN();
  
                  //2. if current log LSN - previous checkpoint > threshold, do checkpoint
                  if (currentLogLSN - lastCheckpointLSN > lsnThreshold) {
  
                      // in check point:
                      //1. get minimum first LSN (MFL) from open indexes.
                      //2. if current MinFirstLSN < targetCheckpointLSN, schedule async flush for any open index witch has first LSN < force flush delta
                      //3. next time checkpoint comes, it will be able to remove log files which have end range less than current targetCheckpointLSN
  
                      targetCheckpointLSN = lastCheckpointLSN + lsnThreshold;
                      currentCheckpointAttemptMinLSN = checkpointManager.tryCheckpoint(targetCheckpointLSN);
  
                      //checkpoint was completed at target LSN or above
                      if (currentCheckpointAttemptMinLSN >= targetCheckpointLSN) {
                          lastCheckpointLSN = currentCheckpointAttemptMinLSN;
                      }
                  }
              } catch (InterruptedException e) {
                  LOGGER.info("Checkpoint thread interrupted", e);
                  Thread.currentThread().interrupt();
              } catch (Exception e) {
                  LOGGER.error("checkpoint attempt failed", e);
              }
          }
      }
  
      public void shutdown() {
          shouldRun = false;
      }
  }
  