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.bookie;
  
  import com.google.common.util.concurrent.RateLimiter;
  import java.io.IOException;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  import org.apache.bookkeeper.conf.ServerConfiguration;
  
  /**
   * Abstract entry log compactor used for compaction.
   */
  public abstract class AbstractLogCompactor {
  
      protected final ServerConfiguration conf;
      protected final Throttler throttler;
  
      /**
       * LogRemovalListener.
       */
      public interface LogRemovalListener {
          void removeEntryLog(long logToRemove);
      }
  
      protected final LogRemovalListener logRemovalListener;
  
      public AbstractLogCompactor(ServerConfiguration conf, LogRemovalListener logRemovalListener) {
          this.conf = conf;
          this.throttler = new Throttler(conf);
          this.logRemovalListener = logRemovalListener;
      }
  
      /**
       * Compact entry log file.
       * @param entryLogMeta log metadata for the entry log to be compacted
       * @return true for succeed
       */
      public abstract boolean compact(EntryLogMetadata entryLogMeta);
  
      /**
       * Do nothing by default. Intended for subclass to override this method.
       */
      public void cleanUpAndRecover() {}
  
      /**
       * class Throttler.
       */
      public static class Throttler {
          private final RateLimiter rateLimiter;
          private final boolean isThrottleByBytes;
          private final AtomicBoolean cancelled = new AtomicBoolean(false);
  
          Throttler(ServerConfiguration conf) {
              this.isThrottleByBytes  = conf.getIsThrottleByBytes();
              this.rateLimiter = RateLimiter.create(this.isThrottleByBytes
                  ? conf.getCompactionRateByBytes() : conf.getCompactionRateByEntries());
          }
  
          // acquire. if bybytes: bytes of this entry; if byentries: 1.
          boolean tryAcquire(int permits, long timeout, TimeUnit unit) {
              return rateLimiter.tryAcquire(this.isThrottleByBytes ? permits : 1, timeout, unit);
          }
  
          // GC thread will check the status for the rate limiter
          // If the compactor is being stopped by other threads,
          // and the GC thread is still limited, the compact task will be stopped.
          public void acquire(int permits) throws IOException {
              long timeout = 100;
              long start = System.currentTimeMillis();
              while (!tryAcquire(permits, timeout, TimeUnit.MILLISECONDS)) {
                  if (cancelled.get()) {
                      throw new IOException("Failed to get permits takes "
                              + (System.currentTimeMillis() - start)
                              + " ms may be compactor has been shutting down");
                  }
                  try {
                      TimeUnit.MILLISECONDS.sleep(timeout);
                  } catch (InterruptedException e) {
                      // ignore
                  }
              }
          }
  
          public void cancelledAcquire() {
              cancelled.set(true);
          }
      }
  
  }
  