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.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import org.apache.bookkeeper.common.concurrent.FutureUtils;
  import org.apache.bookkeeper.versioning.LongVersion;
  import org.apache.commons.lang3.tuple.Pair;
  import org.apache.distributedlog.DLSN;
  import org.apache.distributedlog.ZooKeeperClient;
  import org.apache.distributedlog.api.subscription.SubscriptionStateStore;
  import org.apache.distributedlog.api.subscription.SubscriptionsStore;
  import org.apache.distributedlog.exceptions.DLInterruptedException;
  import org.apache.distributedlog.util.Utils;
  import org.apache.zookeeper.AsyncCallback;
  import org.apache.zookeeper.KeeperException;
  import org.apache.zookeeper.data.Stat;
  
  /**
   * ZooKeeper Based Subscriptions Store.
   */
  public class ZKSubscriptionsStore implements SubscriptionsStore {
  
      private final ZooKeeperClient zkc;
      private final String zkPath;
      private final ConcurrentMap<String, ZKSubscriptionStateStore> subscribers =
              new ConcurrentHashMap<String, ZKSubscriptionStateStore>();
  
      public ZKSubscriptionsStore(ZooKeeperClient zkc, String zkPath) {
          this.zkc = zkc;
          this.zkPath = zkPath;
      }
  
      private ZKSubscriptionStateStore getSubscriber(String subscriberId) {
          ZKSubscriptionStateStore ss = subscribers.get(subscriberId);
          if (ss == null) {
              ZKSubscriptionStateStore newSS = new ZKSubscriptionStateStore(zkc,
                  getSubscriberZKPath(subscriberId));
              ZKSubscriptionStateStore oldSS = subscribers.putIfAbsent(subscriberId, newSS);
              if (oldSS == null) {
                  ss = newSS;
              } else {
                  try {
                      newSS.close();
                  } catch (IOException e) {
                      // ignore the exception
                  }
                  ss = oldSS;
              }
          }
          return ss;
      }
  
      private String getSubscriberZKPath(String subscriberId) {
          return String.format("%s/%s", zkPath, subscriberId);
      }
  
      @Override
      public CompletableFuture<DLSN> getLastCommitPosition(String subscriberId) {
          return getSubscriber(subscriberId).getLastCommitPosition();
      }
  
      @Override
      public CompletableFuture<Map<String, DLSN>> getLastCommitPositions() {
          final CompletableFuture<Map<String, DLSN>> result = new CompletableFuture<Map<String, DLSN>>();
          try {
              this.zkc.get().getChildren(this.zkPath, false, new AsyncCallback.Children2Callback() {
                  @Override
                  public void processResult(int rc, String path, Object ctx, List<String> children, Stat stat) {
                      if (KeeperException.Code.NONODE.intValue() == rc) {
                          result.complete(new HashMap<String, DLSN>());
                      } else if (KeeperException.Code.OK.intValue() != rc) {
                          result.completeExceptionally(KeeperException.create(KeeperException.Code.get(rc), path));
                      } else {
                          getLastCommitPositions(result, children);
                      }
                  }
              }, null);
          } catch (ZooKeeperClient.ZooKeeperConnectionException zkce) {
              result.completeExceptionally(zkce);
          } catch (InterruptedException ie) {
              Thread.currentThread().interrupt();
              result.completeExceptionally(new DLInterruptedException("getLastCommitPositions was interrupted", ie));
          }
          return result;
      }
  
      private void getLastCommitPositions(final CompletableFuture<Map<String, DLSN>> result,
                                          List<String> subscribers) {
          List<CompletableFuture<Pair<String, DLSN>>> futures =
                  new ArrayList<CompletableFuture<Pair<String, DLSN>>>(subscribers.size());
          for (String s : subscribers) {
              final String subscriber = s;
              CompletableFuture<Pair<String, DLSN>> future =
                  // Get the last commit position from zookeeper
                  getSubscriber(subscriber).getLastCommitPositionFromZK().thenApply(
                      dlsn -> Pair.of(subscriber, dlsn));
              futures.add(future);
          }
          FutureUtils.collect(futures).thenAccept((subscriptions) -> {
              Map<String, DLSN> subscriptionMap = new HashMap<String, DLSN>();
              for (Pair<String, DLSN> pair : subscriptions) {
                  subscriptionMap.put(pair.getLeft(), pair.getRight());
              }
              result.complete(subscriptionMap);
          });
      }
  
      @Override
      public CompletableFuture<Void> advanceCommitPosition(String subscriberId, DLSN newPosition) {
          return getSubscriber(subscriberId).advanceCommitPosition(newPosition);
      }
  
      @Override
      public CompletableFuture<Boolean> deleteSubscriber(String subscriberId) {
          subscribers.remove(subscriberId);
          String path = getSubscriberZKPath(subscriberId);
          return Utils.zkDeleteIfNotExist(zkc, path, new LongVersion(-1L));
      }
  
      @Override
      public void close() throws IOException {
          // no-op
          for (SubscriptionStateStore store : subscribers.values()) {
              store.close();
          }
      }
  
  }
  