samza-azure/src/main/java/org/apache/samza/coordinator/scheduler/RenewLeaseScheduler.java

/*
 * 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.samza.coordinator.scheduler;

import com.google.common.util.concurrent.ThreadFactoryBuilder;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import org.apache.samza.util.LeaseBlobManager;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Scheduler class to keep renewing the lease once an entity has acquired it.
 * Renews every 45 seconds.
 * All time units are in SECONDS.
 */
public class RenewLeaseScheduler implements TaskScheduler {

  private static final Logger LOG = LoggerFactory.getLogger(RenewLeaseScheduler.class);
  private static final long RENEW_LEASE_DELAY_SEC = 45;
  private static final ThreadFactory
      PROCESSOR_THREAD_FACTORY = new ThreadFactoryBuilder().setNameFormat("RenewLeaseScheduler-%d").build();
  private final ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(PROCESSOR_THREAD_FACTORY);
  private final LeaseBlobManager leaseBlobManager;
  private final AtomicReference<String> leaseId;
  private final Consumer<String> errorHandler;

  public RenewLeaseScheduler(Consumer<String> errorHandler, LeaseBlobManager leaseBlobManager, AtomicReference<String> leaseId) {
    this.leaseBlobManager = leaseBlobManager;
    this.leaseId = leaseId;
    this.errorHandler = errorHandler;
  }

  @Override
  public ScheduledFuture scheduleTask() {
    return scheduler.scheduleWithFixedDelay(() -> {
      try {
        LOG.info("Renewing lease");
        boolean status = leaseBlobManager.renewLease(leaseId.get());
        if (!status) {
          errorHandler.accept("Unable to renew lease. Continuing as non-leader.");
        }
      } catch (Exception e) {
        errorHandler.accept("Exception in Renew Lease Scheduler. Continuing as non-leader.");
      }
    }, RENEW_LEASE_DELAY_SEC, RENEW_LEASE_DELAY_SEC, TimeUnit.SECONDS);
  }

  @Override
  public void setStateChangeListener(SchedulerStateChangeListener listener) {}

  @Override
  public void shutdown() {
    LOG.info("Shutting down RenewLeaseScheduler Scheduler.");
    scheduler.shutdownNow();
  }
}