ClientProducerCreditsImpl.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
 *
 *     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.
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package org.apache.activemq.artemis.core.client.impl;

import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

import org.apache.activemq.artemis.api.core.ActiveMQException;
import org.apache.activemq.artemis.api.core.ActiveMQInterruptedException;
import org.apache.activemq.artemis.api.core.SimpleString;
import org.apache.activemq.artemis.core.client.ActiveMQClientLogger;
import org.apache.activemq.artemis.core.client.ActiveMQClientMessageBundle;
import org.apache.activemq.artemis.spi.core.remoting.SessionContext;

public class ClientProducerCreditsImpl implements ClientProducerCredits {

   private final Semaphore semaphore;

   private final int windowSize;

   private volatile boolean closed;

   private boolean blocked;

   private final SimpleString address;

   private final ClientSessionInternal session;

   private int pendingCredits;

   private int arriving;

   private int refCount;

   private boolean serverRespondedWithFail;

   private SessionContext sessionContext;

   public ClientProducerCreditsImpl(final ClientSessionInternal session,
                                    final SimpleString address,
                                    final int windowSize) {
      this.session = session;

      this.address = address;

      this.windowSize = windowSize / 2;

      // Doesn't need to be fair since session is single threaded

      semaphore = new Semaphore(0, false);
   }

   @Override
   public void init(SessionContext sessionContext) {
      // We initial request twice as many credits as we request in subsequent requests
      // This allows the producer to keep sending as more arrive, minimising pauses
      checkCredits(windowSize);

      this.sessionContext = sessionContext;

      this.sessionContext.linkFlowControl(address, this);
   }

   @Override
   public void acquireCredits(final int credits) throws ActiveMQException {
      checkCredits(credits);

      boolean tryAcquire;

      synchronized (this) {
         tryAcquire = semaphore.tryAcquire(credits);
      }

      if (!tryAcquire) {
         if (!closed) {
            this.blocked = true;
            try {
               while (!semaphore.tryAcquire(credits, 10, TimeUnit.SECONDS)) {
                  // I'm using string concatenation here in case address is null
                  // better getting a "null" string than a NPE
                  ActiveMQClientLogger.LOGGER.outOfCreditOnFlowControl("" + address);
               }
            } catch (InterruptedException interrupted) {
               Thread.currentThread().interrupt();
               throw new ActiveMQInterruptedException(interrupted);
            } finally {
               this.blocked = false;
            }
         }
      }

      synchronized (this) {
         pendingCredits -= credits;
      }

      // check to see if the blocking mode is FAIL on the server
      synchronized (this) {
         if (serverRespondedWithFail) {
            serverRespondedWithFail = false;

            // remove existing credits to force the client to ask the server for more on the next send
            semaphore.drainPermits();
            pendingCredits = 0;
            arriving = 0;

            throw ActiveMQClientMessageBundle.BUNDLE.addressIsFull(address.toString(), credits);
         }
      }
   }

   @Override
   public boolean isBlocked() {
      return blocked;
   }

   public int getBalance() {
      return semaphore.availablePermits();
   }

   @Override
   public void receiveCredits(final int credits) {
      synchronized (this) {
         arriving -= credits;
      }

      semaphore.release(credits);
   }

   @Override
   public void receiveFailCredits(final int credits) {
      serverRespondedWithFail = true;
      // receive credits like normal to keep the sender from blocking
      receiveCredits(credits);
   }

   @Override
   public synchronized void reset() {
      // Any pendingCredits credits from before failover won't arrive, so we re-initialise

      semaphore.drainPermits();

      int beforeFailure = pendingCredits;

      pendingCredits = 0;
      arriving = 0;

      // If we are waiting for more credits than what's configured, then we need to use what we tried before
      // otherwise the client may starve as the credit will never arrive
      checkCredits(Math.max(windowSize * 2, beforeFailure));
   }

   @Override
   public void close() {
      // Closing a producer that is blocking should make it return
      closed = true;

      semaphore.release(Integer.MAX_VALUE / 2);
   }

   @Override
   public synchronized void incrementRefCount() {
      refCount++;
   }

   @Override
   public synchronized int decrementRefCount() {
      return --refCount;
   }

   @Override
   public synchronized void releaseOutstanding() {
      semaphore.drainPermits();
   }

   private void checkCredits(final int credits) {
      int needed = Math.max(credits, windowSize);

      int toRequest = -1;

      synchronized (this) {
         if (semaphore.availablePermits() + arriving < needed) {
            toRequest = needed - arriving;

            pendingCredits += toRequest;
            arriving += toRequest;
         }
      }

      if (toRequest != -1) {
         requestCredits(toRequest);
      }
   }

   private void requestCredits(final int credits) {
      session.sendProducerCreditsMessage(credits, address);
   }
}