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.bk;
  
  import java.io.IOException;
  import java.util.concurrent.CompletableFuture;
  import org.apache.bookkeeper.client.LedgerHandle;
  import org.apache.bookkeeper.common.concurrent.FutureUtils;
  import org.apache.distributedlog.util.Transaction;
  import org.apache.distributedlog.util.Transaction.OpListener;
  
  
  /**
   * Delegator of the underlying allocator. If it owns the allocator, it takes
   * the responsibility of start the allocator and close the allocator.
   */
  public class LedgerAllocatorDelegator implements LedgerAllocator {
  
      private final LedgerAllocator allocator;
      private final boolean ownAllocator;
  
      /**
       * Create an allocator's delegator.
       *
       * @param allocator
       *          the underlying allocator
       * @param ownAllocator
       *          whether to own the allocator
       */
      public LedgerAllocatorDelegator(LedgerAllocator allocator,
                                      boolean ownAllocator)
              throws IOException {
          this.allocator = allocator;
          this.ownAllocator = ownAllocator;
          if (this.ownAllocator) {
              this.allocator.start();
          }
      }
  
      @Override
      public void start() throws IOException {
          // no-op
      }
  
      @Override
      public CompletableFuture<Void> delete() {
          return FutureUtils.exception(new UnsupportedOperationException("Can't delete an allocator by delegator"));
      }
  
      @Override
      public void allocate() throws IOException {
          this.allocator.allocate();
      }
  
      @Override
      public CompletableFuture<LedgerHandle> tryObtain(Transaction<Object> txn,
                                            OpListener<LedgerHandle> listener) {
          return this.allocator.tryObtain(txn, listener);
      }
  
      @Override
      public CompletableFuture<Void> asyncClose() {
          if (ownAllocator) {
              return this.allocator.asyncClose();
          } else {
              return FutureUtils.value(null);
          }
      }
  }
  