content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.master.block;
  
  import alluxio.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.grpc.GetRegisterLeasePRequest;
  import alluxio.util.CommonUtils;
  import alluxio.wire.RegisterLease;
  
  import com.google.common.base.Preconditions;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Map;
  import java.util.Optional;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.Semaphore;
  
  /**
   * The manager for {@link RegisterLease} that manages the lifecycle for the leases.
   */
  public class RegisterLeaseManager {
    private static final Logger LOG = LoggerFactory.getLogger(RegisterLeaseManager.class);
    private static final long LEASE_TTL_MS =
        Configuration.getMs(PropertyKey.MASTER_WORKER_REGISTER_LEASE_TTL);
  
    private final Semaphore mSemaphore;
    private final Map<Long, RegisterLease> mActiveLeases;
  
    private JvmSpaceReviewer mJvmChecker = null;
  
    /**
     * Constructor.
     */
    public RegisterLeaseManager() {
      int maxConcurrency =
          Configuration.getInt(PropertyKey.MASTER_WORKER_REGISTER_LEASE_COUNT);
      Preconditions.checkState(maxConcurrency > 0, "%s should be greater than 0",
          PropertyKey.MASTER_WORKER_REGISTER_LEASE_COUNT.toString());
      mSemaphore = new Semaphore(maxConcurrency);
  
      if (Configuration.getBoolean(PropertyKey.MASTER_WORKER_REGISTER_LEASE_RESPECT_JVM_SPACE)) {
        mJvmChecker = new JvmSpaceReviewer(Runtime.getRuntime());
      }
  
      mActiveLeases = new ConcurrentHashMap<>();
    }
  
    // If the lease exists, it will be returned
    Optional<RegisterLease> tryAcquireLease(GetRegisterLeasePRequest request) {
      long workerId = request.getWorkerId();
      if (mActiveLeases.containsKey(workerId)) {
        RegisterLease lease = mActiveLeases.get(workerId);
        LOG.info("Found existing lease for worker {}: {}", workerId, lease);
        return Optional.of(lease);
      }
  
      // If the JVM space does not allow, reject the request
      if (mJvmChecker != null && !mJvmChecker.reviewLeaseRequest(request)) {
        return Optional.empty();
      }
  
      // Check for expired leases here instead of having a separate thread.
      // Therefore the recycle is lazy.
      // If no other worker is requesting for a lease, a worker holding an expired lease
      // will still be admitted.
      tryRecycleLease();
  
      if (mSemaphore.tryAcquire()) {
        RegisterLease lease = new RegisterLease(LEASE_TTL_MS);
        mActiveLeases.put(workerId, lease);
        LOG.info("Granted lease to worker {}", workerId);
        return Optional.of(lease);
      }
  
      return Optional.empty();
    }
  
    private void tryRecycleLease() {
      long now = CommonUtils.getCurrentMs();
  
      mActiveLeases.entrySet().removeIf(entry -> {
        long expiry = entry.getValue().mExpiryTimeMs;
        if (expiry < now) {
          LOG.debug("Lease {} has expired and been recycled.", entry.getKey());
          mSemaphore.release();
          return true;
        }
        return false;
      });
    }
  
    boolean hasLease(long workerId) {
      return mActiveLeases.containsKey(workerId);
    }
  
    void releaseLease(long workerId) {
      if (!mActiveLeases.containsKey(workerId)) {
        LOG.info("Worker {}'s lease is not found. Most likely the lease has already been recycled.",
            workerId);
        return;
      }
      mActiveLeases.remove(workerId);
      mSemaphore.release();
    }
  }
  