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.bookkeeper.metadata.etcd;
  
  import static org.apache.bookkeeper.metadata.etcd.EtcdUtils.msResult;
  
  import com.google.common.util.concurrent.ThreadFactoryBuilder;
  import io.etcd.jetcd.Lease;
  import io.etcd.jetcd.lease.LeaseKeepAliveResponse;
  import io.etcd.jetcd.support.CloseableClient;
  import io.grpc.stub.StreamObserver;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  import java.util.function.Supplier;
  import lombok.AccessLevel;
  import lombok.Getter;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.bookkeeper.bookie.BookieException.MetadataStoreException;
  import org.apache.bookkeeper.common.concurrent.FutureUtils;
  import org.apache.bookkeeper.discover.RegistrationManager.RegistrationListener;
  
  /**
   * Register to register a bookie in Etcd.
   */
  @Slf4j
  class EtcdBookieRegister implements AutoCloseable, Runnable, Supplier<Long> {
  
      private final Lease leaseClient;
      private final long ttlSeconds;
      private final ScheduledExecutorService executor;
      private RegistrationListener regListener;
      private volatile CompletableFuture<Long> leaseFuture = new CompletableFuture<>();
      private volatile CompletableFuture<Void> keepAliveFuture = new CompletableFuture<>();
  
      @Getter(AccessLevel.PACKAGE)
      private volatile long leaseId = -0xabcd;
      private volatile CloseableClient kaListener = null;
      private volatile boolean running = true;
      private long nextWaitTimeMs = 200;
      private Future<?> runFuture = null;
  
      EtcdBookieRegister(Lease leaseClient,
                         long ttlSeconds) {
          this.leaseClient = leaseClient;
          this.ttlSeconds = ttlSeconds;
          this.executor = Executors.newSingleThreadScheduledExecutor(
              new ThreadFactoryBuilder()
                  .setNameFormat("bookie-etcd-keepalive-thread")
                  .build());
      }
  
      public EtcdBookieRegister addRegistrationListener(RegistrationListener regListener) {
          this.regListener = regListener;
          return this;
      }
  
      long getTtlSeconds() {
          return ttlSeconds;
      }
  
      public synchronized EtcdBookieRegister start() {
          if (null == runFuture) {
              runFuture = executor.submit(this);
          }
          return this;
      }
  
      private void newLeaseIfNeeded() throws MetadataStoreException {
          boolean newLeaseNeeded;
          synchronized (this) {
              newLeaseNeeded = !leaseFuture.isDone();
          }
          if (newLeaseNeeded) {
              long leaseId = msResult(leaseClient.grant(ttlSeconds)).getID();
              keepAliveFuture = new CompletableFuture<>();
              if (kaListener != null) {
                  synchronized (this) {
                      kaListener.close();
                      kaListener = null;
                  }
              }
              this.kaListener = leaseClient.keepAlive(leaseId, new StreamObserver<LeaseKeepAliveResponse>() {
                  @Override
                  public void onNext(LeaseKeepAliveResponse response) {
                      log.info("KeepAlive response : lease = {}, ttl = {}",
                              response.getID(), response.getTTL());
                  }
  
                  @Override
                  public void onError(Throwable t) {
                      log.info("KeepAlive renewal failed, leaseId {}", leaseId, t.fillInStackTrace());
                      keepAliveFuture.completeExceptionally(t);
                  }
  
                  @Override
                  public void onCompleted() {
                      log.info("lease completed! leaseId {}", leaseId);
                      keepAliveFuture.cancel(true);
                  }
              });
  
              this.leaseId = leaseId;
              leaseFuture.complete(leaseId);
              log.info("New lease '{}' is granted.", leaseId);
          }
      }
  
      private void waitForNewLeaseId() {
          while (running) {
              try {
                  newLeaseIfNeeded();
                  nextWaitTimeMs = 100L;
              } catch (MetadataStoreException e) {
                  log.error("Failed to grant a new lease for leaseId {}", leaseId, e);
                  try {
                      TimeUnit.MILLISECONDS.sleep(nextWaitTimeMs);
                      nextWaitTimeMs *= 2;
                      nextWaitTimeMs = Math.min(nextWaitTimeMs, TimeUnit.SECONDS.toMillis(ttlSeconds));
                  } catch (InterruptedException e1) {
                      Thread.currentThread().interrupt();
                      log.warn("Interrupted at backing off granting a new lease for leaseId {}", leaseId);
                  }
                  continue;
              }
          }
      }
  
      @Override
      public void run() {
          while (running) {
              waitForNewLeaseId();
              // here we get a lease, keep it alive
              try {
                  log.info("Keeping Alive at lease = {}", get());
                  keepAliveFuture.get();
                  continue;
              } catch (InterruptedException ie) {
                  Thread.currentThread().interrupt();
                  log.warn("Interrupted at keeping lease '{}' alive", leaseId);
                  resetLease();
              } catch (ExecutionException ee) {
                  log.warn("Failed to keep alive lease '{}'", leaseId, ee);
                  resetLease();
              }
          }
      }
  
      private void resetLease() {
          synchronized (this) {
              leaseFuture = new CompletableFuture<>();
          }
          if (null != regListener) {
              regListener.onRegistrationExpired();
          }
      }
  
      @Override
      public void close() {
          synchronized (this) {
              if (!running) {
                  return;
              } else {
                  running = false;
              }
              if (null != runFuture) {
                  if (runFuture.cancel(true)) {
                      log.info("Successfully interrupted bookie register.");
                  }
              }
              keepAliveFuture.cancel(true);
              if (kaListener != null) {
                  kaListener.close();
                  kaListener = null;
              }
          }
          CompletableFuture<Void> closeFuture = new CompletableFuture<>();
          executor.submit(() -> {
              FutureUtils.complete(closeFuture, (Void) null);
          });
          closeFuture.join();
      }
  
      @Override
      public Long get() {
          while (true) {
              try {
                  return leaseFuture.get(100, TimeUnit.MILLISECONDS);
              } catch (InterruptedException e) {
                  log.warn("Interrupted at getting lease id", e);
                  return -1L;
              } catch (ExecutionException e) {
                  throw new IllegalArgumentException("Should never reach here");
              } catch (TimeoutException e) {
                  continue;
              }
  
          }
      }
  
  }
  