order

This paper focuses on the graceful shutdown enabled of artemis

gracefulShutdownEnabled

activemq-artemis-2.11.0/artemis-server/src/main/java/org/apache/activemq/artemis/core/config/impl/ConfigurationImpl.java

public class ConfigurationImpl implements Configuration, Serializable {

   //......

   private boolean gracefulShutdownEnabled = ActiveMQDefaultConfiguration.isDefaultGracefulShutdownEnabled();

   private long gracefulShutdownTimeout = ActiveMQDefaultConfiguration.getDefaultGracefulShutdownTimeout();

   //......

   @Override
   public boolean isGracefulShutdownEnabled() {
      return gracefulShutdownEnabled;
   }

   @Override
   public ConfigurationImpl setGracefulShutdownEnabled(final boolean enabled) {
      gracefulShutdownEnabled = enabled;
      return this;
   }

   @Override
   public long getGracefulShutdownTimeout() {
      return gracefulShutdownTimeout;
   }

   @Override
   public ConfigurationImpl setGracefulShutdownTimeout(final long timeout) {
      gracefulShutdownTimeout = timeout;
      return this;
   }

   //......
}

• ConfigurationImpl defines two properties about gracefulShutdown, which are gracefulShutdown enabled (default is true) and gracefulShutdown timeout (default is - 1)

ActiveMQServerImpl

activemq-artemis-2.11.0/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/ActiveMQServerImpl.java

public class ActiveMQServerImpl implements ActiveMQServer {

   //......

   public final void stop(boolean failoverOnServerShutdown, boolean isExit) throws Exception {
      stop(failoverOnServerShutdown, false, false, isExit);
   }

   public void stop(boolean failoverOnServerShutdown, final boolean criticalIOError, boolean restarting) {
      this.stop(failoverOnServerShutdown, criticalIOError, restarting, false);
   }

   void stop(boolean failoverOnServerShutdown, final boolean criticalIOError, boolean restarting, boolean isShutdown) {

      logger.debug("Stopping server");

      synchronized (this) {
         if (state == SERVER_STATE.STOPPED || state == SERVER_STATE.STOPPING) {
            return;
         }
         state = SERVER_STATE.STOPPING;

         if (fileStoreMonitor != null) {
            fileStoreMonitor.stop();
            fileStoreMonitor = null;
         }

         if (failoverOnServerShutdown) {
            activation.sendLiveIsStopping();
         }

         stopComponent(connectorsService);

         // we stop the groupingHandler before we stop the cluster manager so binding mappings
         // aren't removed in case of failover
         if (groupingHandler != null) {
            managementService.removeNotificationListener(groupingHandler);
            stopComponent(groupingHandler);
         }
         stopComponent(federationManager);
         stopComponent(clusterManager);

         if (remotingService != null) {
            remotingService.pauseAcceptors();
         }

         // allows for graceful shutdown
         if (remotingService != null && configuration.isGracefulShutdownEnabled()) {
            long timeout = configuration.getGracefulShutdownTimeout();
            try {
               if (timeout == -1) {
                  remotingService.getConnectionCountLatch().await();
               } else {
                  remotingService.getConnectionCountLatch().await(timeout);
               }
            } catch (InterruptedException e) {
               ActiveMQServerLogger.LOGGER.interruptWhilstStoppingComponent(remotingService.getClass().getName());
            }
         }

         freezeConnections();
      }

      //......

    }

   static void stopComponent(ActiveMQComponent component) {
      try {
         if (component != null) {
            component.stop();
         }
      } catch (Throwable t) {
         ActiveMQServerLogger.LOGGER.errorStoppingComponent(t, component.getClass().getName());
      }
   }

   //......

}    

• ActiveMQServerImpl will read configuration. Getgracefullshutdown timeout() when remotingService is not null and configuration. Isgracefullshutdown enabled() is true; if timeout is - 1, remotingService.getConnectionCountLatch().await() will be executed; otherwise, remotingService.getConnectionCountLatch().await(timeout) will be executed

connectionCountLatch

activemq-artemis-2.11.0/artemis-server/src/main/java/org/apache/activemq/artemis/core/remoting/server/impl/RemotingServiceImpl.java

public class RemotingServiceImpl implements RemotingService, ServerConnectionLifeCycleListener {

   //......

   private final ReusableLatch connectionCountLatch = new ReusableLatch(0);

   //......

   public synchronized ReusableLatch getConnectionCountLatch() {
      return connectionCountLatch;
   }

   public void connectionCreated(final ActiveMQComponent component,
                                 final Connection connection,
                                 final ProtocolManager protocol) {
      if (server == null) {
         throw new IllegalStateException("Unable to create connection, server hasn't finished starting up");
      }

      ConnectionEntry entry = protocol.createConnectionEntry((Acceptor) component, connection);
      try {
         if (server.hasBrokerConnectionPlugins()) {
            server.callBrokerConnectionPlugins(plugin -> plugin.afterCreateConnection(entry.connection));
         }
      } catch (ActiveMQException t) {
         logger.warn("Error executing afterCreateConnection plugin method: {}", t.getMessage(), t);
         throw new IllegalStateException(t.getMessage(), t.getCause());

      }
      if (logger.isTraceEnabled()) {
         logger.trace("Connection created " + connection);
      }

      connections.put(connection.getID(), entry);
      connectionCountLatch.countUp();
      totalConnectionCount.incrementAndGet();
   }

   public RemotingConnection removeConnection(final Object remotingConnectionID) {
      ConnectionEntry entry = connections.remove(remotingConnectionID);

      if (entry != null) {
         logger.debug("RemotingServiceImpl::removing connection ID " + remotingConnectionID);
         connectionCountLatch.countDown();
         return entry.connection;
      } else {
         logger.debug("The connectionID::" + remotingConnectionID + " was already removed by some other module");

         return null;
      }
   }

   //......

}         

• getConnectionCountLatch returns connectionCountLatch; connectionCreated method will execute connectionCountLatch.countUp(); removeConnection method will execute connectionCountLatch.countDown()

Summary

ConfigurationImpl defines two properties about gracefulShutdown, which are gracefulShutdown enabled (default is true) and gracefulShutdown timeout (default is - 1). ActiveMQServerImpl will read configuration. Getgracefulshutdown timeout() when remotingService is not null and configuration. Isgracefulshutdown enabled() is true. If timeout is - 1, remotingservi will be executed CE. Getconnectioncountlatch(). Await(), otherwise execute remotingService.getConnectionCountLatch().await(timeout)

doc

• ConfigurationImpl