聊聊artemis的callFailoverTimeout

序

本文主要研究一下artemis的callFailoverTimeout

establishNewConnection

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/client/impl/ClientSessionFactoryImpl.java

public class ClientSessionFactoryImpl implements ClientSessionFactoryInternal, ClientConnectionLifeCycleListener {

   //......

   protected RemotingConnection establishNewConnection() {
      Connection transportConnection = createTransportConnection();

      if (transportConnection == null) {
         if (ClientSessionFactoryImpl.logger.isTraceEnabled()) {
            logger.trace("Neither backup or live were active, will just give up now");
         }
         return null;
      }

      RemotingConnection newConnection = clientProtocolManager.connect(transportConnection, callTimeout, callFailoverTimeout, incomingInterceptors, outgoingInterceptors, new SessionFactoryTopologyHandler());

      newConnection.addFailureListener(new DelegatingFailureListener(newConnection.getID()));

      schedulePing();

      if (logger.isTraceEnabled()) {
         logger.trace("returning " + newConnection);
      }

      return newConnection;
   }

   //......
}

• ClientSessionFactoryImpl的establishNewConnection通过clientProtocolManager.connect创建RemotingConnection

ActiveMQClientProtocolManager

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/protocol/core/impl/ActiveMQClientProtocolManager.java

public class ActiveMQClientProtocolManager implements ClientProtocolManager {

   //......

   public RemotingConnection connect(Connection transportConnection,
                                     long callTimeout,
                                     long callFailoverTimeout,
                                     List incomingInterceptors,
                                     List outgoingInterceptors,
                                     TopologyResponseHandler topologyResponseHandler) {
      this.connection = new RemotingConnectionImpl(createPacketDecoder(), transportConnection, callTimeout, callFailoverTimeout, incomingInterceptors, outgoingInterceptors, executor);

      this.topologyResponseHandler = topologyResponseHandler;

      getChannel0().setHandler(new Channel0Handler(connection));

      sendHandshake(transportConnection);

      return connection;
   }

   //......
}

• ActiveMQClientProtocolManager的connect方法创建了RemotingConnectionImpl

RemotingConnectionImpl

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/protocol/core/impl/RemotingConnectionImpl.java

public class RemotingConnectionImpl extends AbstractRemotingConnection implements CoreRemotingConnection {

   //......

   private final long blockingCallTimeout;

   private final long blockingCallFailoverTimeout;

   //......

   public RemotingConnectionImpl(final PacketDecoder packetDecoder,
                                 final Connection transportConnection,
                                 final long blockingCallTimeout,
                                 final long blockingCallFailoverTimeout,
                                 final List incomingInterceptors,
                                 final List outgoingInterceptors,
                                 final Executor connectionExecutor) {
      this(packetDecoder, transportConnection, blockingCallTimeout, blockingCallFailoverTimeout, incomingInterceptors, outgoingInterceptors, true, null, connectionExecutor);
   }

   private RemotingConnectionImpl(final PacketDecoder packetDecoder,
                                  final Connection transportConnection,
                                  final long blockingCallTimeout,
                                  final long blockingCallFailoverTimeout,
                                  final List incomingInterceptors,
                                  final List outgoingInterceptors,
                                  final boolean client,
                                  final SimpleString nodeID,
                                  final Executor connectionExecutor) {
      super(transportConnection, connectionExecutor);

      this.packetDecoder = packetDecoder;

      this.blockingCallTimeout = blockingCallTimeout;

      this.blockingCallFailoverTimeout = blockingCallFailoverTimeout;

      this.incomingInterceptors = incomingInterceptors;

      this.outgoingInterceptors = outgoingInterceptors;

      this.client = client;

      this.nodeID = nodeID;

      transportConnection.setProtocolConnection(this);

      if (logger.isTraceEnabled()) {
         logger.trace("RemotingConnectionImpl created: " + this);
      }
   }

   @Override
   public long getBlockingCallTimeout() {
      return blockingCallTimeout;
   }

   @Override
   public long getBlockingCallFailoverTimeout() {
      return blockingCallFailoverTimeout;
   }

   //......
}   

• RemotingConnectionImpl定义了blockingCallFailoverTimeout属性

waitForFailOver

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/protocol/core/impl/ChannelImpl.java

public final class ChannelImpl implements Channel {

   //......

   private final Lock lock = new ReentrantLock();

   private final Condition sendCondition = lock.newCondition();

   private final Condition failoverCondition = lock.newCondition();

   private boolean failingOver;

   //......

   private void waitForFailOver(String timeoutMsg) {
      try {
         if (connection.getBlockingCallFailoverTimeout() < 0) {
            while (failingOver) {
               failoverCondition.await();
            }
         } else if (!ConcurrentUtil.await(failoverCondition, connection.getBlockingCallFailoverTimeout())) {
            logger.debug(timeoutMsg);
         }
      } catch (InterruptedException e) {
         throw new ActiveMQInterruptedException(e);
      }
   }

   private boolean send(final Packet packet, final int reconnectID, final boolean flush, final boolean batch) {
      if (invokeInterceptors(packet, interceptors, connection) != null) {
         return false;
      }

      synchronized (sendLock) {
         packet.setChannelID(id);

         if (responseAsyncCache != null && packet.isRequiresResponse() && packet.isResponseAsync()) {
            packet.setCorrelationID(responseAsyncCache.nextCorrelationID());
         }

         if (logger.isTraceEnabled()) {
            logger.trace("RemotingConnectionID=" + (connection == null ? "NULL" : connection.getID()) + " Sending packet nonblocking " + packet + " on channelID=" + id);
         }

         ActiveMQBuffer buffer = packet.encode(connection);

         lock.lock();

         try {
            if (failingOver) {
               waitForFailOver("RemotingConnectionID=" + (connection == null ? "NULL" : connection.getID()) + " timed-out waiting for fail-over condition on non-blocking send");
            }

            // Sanity check
            if (transferring) {
               throw ActiveMQClientMessageBundle.BUNDLE.cannotSendPacketDuringFailover();
            }

            if (resendCache != null && packet.isRequiresConfirmations()) {
               addResendPacket(packet);
            }

         } finally {
            lock.unlock();
         }

         if (logger.isTraceEnabled()) {
            logger.trace("RemotingConnectionID=" + (connection == null ? "NULL" : connection.getID()) + " Writing buffer for channelID=" + id);
         }

         checkReconnectID(reconnectID);

         //We do this outside the lock as ResponseCache is threadsafe and allows responses to come in,
         //As the send could block if the response cache cannot add, preventing responses to be handled.
         if (responseAsyncCache != null && packet.isRequiresResponse() && packet.isResponseAsync()) {
            while (!responseAsyncCache.add(packet)) {
               try {
                  Thread.sleep(1);
               } catch (Exception e) {
                  // Ignore
               }
            }
         }

         // The actual send must be outside the lock, or with OIO transport, the write can block if the tcp
         // buffer is full, preventing any incoming buffers being handled and blocking failover
         try {
            connection.getTransportConnection().write(buffer, flush, batch);
         } catch (Throwable t) {
            //If runtime exception, we must remove from the cache to avoid filling up the cache causing it to be full.
            //The client would get still know about this as the exception bubbles up the call stack instead.
            if (responseAsyncCache != null && packet.isRequiresResponse() && packet.isResponseAsync()) {
               responseAsyncCache.remove(packet.getCorrelationID());
            }
            throw t;
         }
         return true;
      }
   }

   @Override
   public void lock() {
      if (logger.isTraceEnabled()) {
         logger.trace("RemotingConnectionID=" + (connection == null ? "NULL" : connection.getID()) + " lock channel " + this);
      }
      lock.lock();

      reconnectID.incrementAndGet();

      failingOver = true;

      lock.unlock();
   }

   @Override
   public void unlock() {
      if (logger.isTraceEnabled()) {
         logger.trace("RemotingConnectionID=" + (connection == null ? "NULL" : connection.getID()) + " unlock channel " + this);
      }
      lock.lock();

      failingOver = false;

      failoverCondition.signalAll();

      lock.unlock();
   }

   //......
}

• ChannelImpl的waitForFailOver在connection.getBlockingCallFailoverTimeout()大于等于0的时候执行ConcurrentUtil.await(failoverCondition, connection.getBlockingCallFailoverTimeout())；send方法在failingOver为true时会执行waitForFailOver方法；其lock方法会设置failingOver为true，unlock方法会设置failingOver为false

ActiveMQSessionContext

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/protocol/core/impl/ActiveMQSessionContext.java

public class ActiveMQSessionContext extends SessionContext {

   //......

   private final Channel sessionChannel;

   //......

   @Override
   public void lockCommunications() {
      sessionChannel.lock();
   }

   @Override
   public void releaseCommunications() {
      sessionChannel.setTransferring(false);
      sessionChannel.unlock();
   }

   //......
}

• ActiveMQSessionContext的lockCommunications方法会执行sessionChannel.lock()，而releaseCommunications会执行sessionChannel.unlock()

ClientSessionImpl

activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/client/impl/ClientSessionImpl.java

public final class ClientSessionImpl implements ClientSessionInternal, FailureListener {

   //......

   public void preHandleFailover(RemotingConnection connection) {
      // We lock the channel to prevent any packets to be added to the re-send
      // cache during the failover process
      //we also do this before the connection fails over to give the session a chance to block for failover
      sessionContext.lockCommunications();
   }

   public boolean handleFailover(final RemotingConnection backupConnection, ActiveMQException cause) {
      boolean suc = true;

      synchronized (this) {
         if (closed) {
            return true;
         }

         boolean resetCreditManager = false;

         try {

            // TODO remove this and encapsulate it

            boolean reattached = sessionContext.reattachOnNewConnection(backupConnection);

            if (!reattached) {

               // We change the name of the Session, otherwise the server could close it while we are still sending the recreate
               // in certain failure scenarios
               // For instance the fact we didn't change the name of the session after failover or reconnect
               // was the reason allowing multiple Sessions to be closed simultaneously breaking concurrency
               this.name = UUIDGenerator.getInstance().generateStringUUID();

               sessionContext.resetName(name);

               Map clonedConsumerEntries = cloneConsumerEntries();

               for (ClientConsumerInternal consumer : clonedConsumerEntries.values()) {
                  consumer.clearAtFailover();
               }

               // The session wasn't found on the server - probably we're failing over onto a backup server where the
               // session won't exist or the target server has been restarted - in this case the session will need to be
               // recreated,
               // and we'll need to recreate any consumers

               // It could also be that the server hasn't been restarted, but the session is currently executing close,
               // and
               // that
               // has already been executed on the server, that's why we can't find the session- in this case we *don't*
               // want
               // to recreate the session, we just want to unblock the blocking call
               if (!inClose && mayAttemptToFailover) {
                  sessionContext.recreateSession(username, password, minLargeMessageSize, xa, autoCommitSends, autoCommitAcks, preAcknowledge);

                  for (Map.Entry entryx : clonedConsumerEntries.entrySet()) {

                     ClientConsumerInternal consumerInternal = entryx.getValue();
                     synchronized (consumerInternal) {
                        if (!consumerInternal.isClosed()) {
                           sessionContext.recreateConsumerOnServer(consumerInternal, entryx.getKey().getId(), started);
                        }
                     }
                  }

                  if ((!autoCommitAcks || !autoCommitSends) && workDone) {
                     // this is protected by a lock, so we can guarantee nothing will sneak here
                     // while we do our work here
                     rollbackOnly = true;
                  }
                  if (currentXID != null) {
                     sessionContext.xaFailed(currentXID);
                     rollbackOnly = true;
                  }

                  // Now start the session if it was already started
                  if (started) {
                     for (ClientConsumerInternal consumer : clonedConsumerEntries.values()) {
                        consumer.clearAtFailover();
                        consumer.start();
                     }

                     sessionContext.restartSession();
                  }

                  resetCreditManager = true;
               }

               sessionContext.returnBlocking(cause);
            }
         } catch (Throwable t) {
            ActiveMQClientLogger.LOGGER.failedToHandleFailover(t);
            suc = false;
         } finally {
            sessionContext.releaseCommunications();
         }

         if (resetCreditManager) {
            synchronized (producerCreditManager) {
               producerCreditManager.reset();
            }

            // Also need to send more credits for consumers, otherwise the system could hand with the server
            // not having any credits to send
         }
      }

      HashMap metaDataToSend;

      synchronized (metadata) {
         metaDataToSend = new HashMap<>(metadata);
      }

      sessionContext.resetMetadata(metaDataToSend);

      return suc;

   }

   //......
}   

• ClientSessionImpl的preHandleFailover方法会执行sessionContext.lockCommunications()，而handleFailover方法在recreateConsumerOnServer之后的finally里头会执行sessionContext.releaseCommunications()

小结

RemotingConnectionImpl定义了blockingCallFailoverTimeout属性；ChannelImpl的waitForFailOver在connection.getBlockingCallFailoverTimeout()大于等于0的时候执行ConcurrentUtil.await(failoverCondition, connection.getBlockingCallFailoverTimeout())；send方法在failingOver为true时会执行waitForFailOver方法；其lock方法会设置failingOver为true，unlock方法会设置failingOver为false

doc

• RemotingConnectionImpl