SizeAwareMettric.java

/**
 * 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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.activemq.artemis.utils;

import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
import java.util.concurrent.atomic.AtomicLongFieldUpdater;
import java.util.function.IntConsumer;

import org.jboss.logging.Logger;

public class SizeAwareMetric {

   private static final Logger logger = Logger.getLogger(SizeAwareMetric.class);

   private static final AtomicLongFieldUpdater<SizeAwareMetric> elementsUpdater = AtomicLongFieldUpdater.newUpdater(SizeAwareMetric.class, "elements");
   private volatile long elements;

   private static final AtomicLongFieldUpdater<SizeAwareMetric> sizeUpdater = AtomicLongFieldUpdater.newUpdater(SizeAwareMetric.class, "elements");
   private volatile long size;

   private static final AtomicIntegerFieldUpdater<SizeAwareMetric> overFlagUpdater = AtomicIntegerFieldUpdater.newUpdater(SizeAwareMetric.class, "overFlag");
   private volatile int overFlag;

   public boolean isOver() {
      return overFlag != 0;
   }

   private final long maxSize;

   private final long lowerMark;

   private IntConsumer[] onSizeSlots;

   private Runnable[] overSlots;

   private Runnable[] underSlots;

   public SizeAwareMetric(long maxSize, long lowerMark, IntConsumer[] onSizeSlots, Runnable[] overSlots, Runnable[] underSlots) {
      this.maxSize = maxSize;
      this.lowerMark = lowerMark;
      this.onSizeSlots = onSizeSlots;
      this.overSlots = overSlots;
      this.underSlots = underSlots;
   }

   protected void over() {
      if (overSlots != null) {
         for (Runnable over: overSlots) {
            if (over != null) {
               try {
                  over.run();
               } catch (Throwable e) {
                  logger.warn(e.getMessage(), e);
               }
            }
         }
      }
   }

   protected void under() {
      if (underSlots != null) {
         for (Runnable under: underSlots) {
            if (under != null) {
               try {
                  under.run();
               } catch (Throwable e) {
                  logger.warn(e.getMessage(), e);
               }
            }
         }
      }
   }

   private boolean changeOverFlag(int expected, int newValue) {
      return overFlagUpdater.compareAndSet(this, expected, newValue);
   }

   public long addSize(int delta) {
      if (delta == 0) {
         throw new IllegalStateException("Size must be > 0");
      }

      if (onSizeSlots != null) {
         for (IntConsumer theFunction : onSizeSlots) {
            theFunction.accept(delta);
         }
      }

      long currentSize = sizeUpdater.addAndGet(this, delta);

      if (delta > 0) {
         elementsUpdater.incrementAndGet(this);
         if (currentSize >= maxSize && changeOverFlag(0, 1)) {
            over();
         }
      } else if (delta < 0) {
         elementsUpdater.decrementAndGet(this);
         if (currentSize <= lowerMark && changeOverFlag(1, 0)) {
            under();
         }
      }

      return currentSize;
   }

}