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.distributedlog.impl.subscription;
  
  
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  import org.apache.bookkeeper.common.concurrent.FutureUtils;
  import org.apache.distributedlog.DLSN;
  import org.apache.distributedlog.ZooKeeperClient;
  import org.apache.distributedlog.api.subscription.SubscriptionStateStore;
  import org.apache.distributedlog.exceptions.DLInterruptedException;
  import org.apache.distributedlog.util.Utils;
  import org.apache.zookeeper.AsyncCallback;
  import org.apache.zookeeper.CreateMode;
  import org.apache.zookeeper.KeeperException;
  import org.apache.zookeeper.data.Stat;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  /**
   * The subscription state store Implementation.
   */
  public class ZKSubscriptionStateStore implements SubscriptionStateStore {
  
      private static final Logger logger = LoggerFactory.getLogger(ZKSubscriptionStateStore.class);
  
      private final ZooKeeperClient zooKeeperClient;
      private final String zkPath;
      private static final AtomicReferenceFieldUpdater<ZKSubscriptionStateStore, DLSN> lastCommittedPositionUpdater =
          AtomicReferenceFieldUpdater.newUpdater(ZKSubscriptionStateStore.class, DLSN.class, "lastCommittedPosition");
      private volatile DLSN lastCommittedPosition = null;
  
      public ZKSubscriptionStateStore(ZooKeeperClient zooKeeperClient, String zkPath) {
          this.zooKeeperClient = zooKeeperClient;
          this.zkPath = zkPath;
      }
  
      @Override
      public void close() throws IOException {
      }
  
      /**
       * Get the last committed position stored for this subscription.
       */
      @Override
      public CompletableFuture<DLSN> getLastCommitPosition() {
          DLSN dlsn = lastCommittedPositionUpdater.get(this);
          if (null != dlsn) {
              return FutureUtils.value(dlsn);
          } else {
              return getLastCommitPositionFromZK();
          }
      }
  
      CompletableFuture<DLSN> getLastCommitPositionFromZK() {
          final CompletableFuture<DLSN> result = new CompletableFuture<DLSN>();
          try {
              logger.debug("Reading last commit position from path {}", zkPath);
              zooKeeperClient.get().getData(zkPath, false, new AsyncCallback.DataCallback() {
                  @Override
                  public void processResult(int rc, String path, Object ctx, byte[] data, Stat stat) {
                      logger.debug("Read last commit position from path {}: rc = {}", zkPath, rc);
                      if (KeeperException.Code.NONODE.intValue() == rc) {
                          result.complete(DLSN.NonInclusiveLowerBound);
                      } else if (KeeperException.Code.OK.intValue() != rc) {
                          result.completeExceptionally(KeeperException.create(KeeperException.Code.get(rc), path));
                      } else {
                          try {
                              DLSN dlsn = DLSN.deserialize(new String(data, StandardCharsets.UTF_8));
                              result.complete(dlsn);
                          } catch (Exception t) {
                              logger.warn("Invalid last commit position found from path {}", zkPath, t);
                              // invalid dlsn recorded in subscription state store
                              result.complete(DLSN.NonInclusiveLowerBound);
                          }
                      }
                  }
              }, null);
          } catch (ZooKeeperClient.ZooKeeperConnectionException zkce) {
              result.completeExceptionally(zkce);
          } catch (InterruptedException ie) {
              Thread.currentThread().interrupt();
              result.completeExceptionally(new DLInterruptedException("getLastCommitPosition was interrupted", ie));
          }
          return result;
      }
  
      /**
       * Advances the position associated with the subscriber.
       *
       * @param newPosition - new commit position
       */
      @Override
      public CompletableFuture<Void> advanceCommitPosition(DLSN newPosition) {
          DLSN dlsn = lastCommittedPositionUpdater.get(this);
          if (null == dlsn
                  || (newPosition.compareTo(dlsn) > 0)) {
              lastCommittedPositionUpdater.set(this, newPosition);
              return Utils.zkAsyncCreateFullPathOptimisticAndSetData(zooKeeperClient,
                  zkPath, newPosition.serialize().getBytes(StandardCharsets.UTF_8),
                  zooKeeperClient.getDefaultACL(),
                  CreateMode.PERSISTENT);
          } else {
              return FutureUtils.Void();
          }
      }
  }
  