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.cassandra.index.sai.utils;
  
  import java.util.concurrent.atomic.AtomicLong;
  import javax.annotation.concurrent.ThreadSafe;
  
  import com.google.common.annotations.VisibleForTesting;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.utils.FBUtilities;
  
  /**
   * A simple, thread-safe memory usage tracker, named to reflect a particular scope.
   */
  @ThreadSafe
  public final class NamedMemoryLimiter
  {
      private static final Logger logger = LoggerFactory.getLogger(NamedMemoryLimiter.class);
      
      private final AtomicLong bytesUsed = new AtomicLong(0);
      private final String scope;
  
      private long limitBytes;
  
      public NamedMemoryLimiter(long limitBytes, String scope)
      {
          this.limitBytes = limitBytes;
          this.scope = scope;
  
          logger.info("[{}]: Memory limiter using limit of {}...", scope, FBUtilities.prettyPrintMemory(limitBytes));
      }
  
      /**
       * @return true if the current number of bytes allocated against the tracker has breached the limit, false otherwise
       */
      public boolean usageExceedsLimit()
      {
          return currentBytesUsed() > limitBytes;
      }
  
      public long increment(long bytes)
      {
          if (logger.isTraceEnabled())
              logger.trace("[{}]: Incrementing tracked memory usage by {} bytes from current usage of {}...", scope, bytes, currentBytesUsed());
          return bytesUsed.addAndGet(bytes);
      }
  
      public long decrement(long bytes)
      {
          if (logger.isTraceEnabled())
              logger.trace("[{}]: Decrementing tracked memory usage by {} bytes from current usage of {}...", scope, bytes, currentBytesUsed());
          return bytesUsed.addAndGet(-bytes);
      }
  
      public long currentBytesUsed()
      {
          return bytesUsed.get();
      }
      
      public long limitBytes()
      {
          return limitBytes;
      }
  
      @VisibleForTesting
      public void setLimitBytes(long bytes)
      {
          limitBytes = bytes;
      }
  }
  