聊聊dubbo的ConnectionOrderedDispatcher

序

本文主要研究一下 dubbo 的 ConnectionOrderedDispatcher

ConnectionOrderedDispatcher

dubbo-2.7.3/dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/transport/dispatcher/connection/ConnectionOrderedDispatcher.java

public class ConnectionOrderedDispatcher implements Dispatcher {

    public static final String NAME = "connection";

    @Override
    public ChannelHandler dispatch(ChannelHandler handler, URL url) {return new ConnectionOrderedChannelHandler(handler, url);
    }

}

• ConnectionOrderedDispatcher 实现了 Dispatcher 接口，其 dispatch 方法返回的是 ConnectionOrderedChannelHandler

ConnectionOrderedChannelHandler

dubbo-2.7.3/dubbo-remoting/dubbo-remoting-api/src/main/java/org/apache/dubbo/remoting/transport/dispatcher/connection/ConnectionOrderedChannelHandler.java

public class ConnectionOrderedChannelHandler extends WrappedChannelHandler {

    protected final ThreadPoolExecutor connectionExecutor;
    private final int queuewarninglimit;

    public ConnectionOrderedChannelHandler(ChannelHandler handler, URL url) {super(handler, url);
        String threadName = url.getParameter(THREAD_NAME_KEY, DEFAULT_THREAD_NAME);
        connectionExecutor = new ThreadPoolExecutor(1, 1,
                0L, TimeUnit.MILLISECONDS,
                new LinkedBlockingQueue<Runnable>(url.getPositiveParameter(CONNECT_QUEUE_CAPACITY, Integer.MAX_VALUE)),
                new NamedThreadFactory(threadName, true),
                new AbortPolicyWithReport(threadName, url)
        );  // FIXME There's no place to release connectionExecutor!
        queuewarninglimit = url.getParameter(CONNECT_QUEUE_WARNING_SIZE, DEFAULT_CONNECT_QUEUE_WARNING_SIZE);
    }

    @Override
    public void connected(Channel channel) throws RemotingException {
        try {checkQueueLength();
            connectionExecutor.execute(new ChannelEventRunnable(channel, handler, ChannelState.CONNECTED));
        } catch (Throwable t) {throw new ExecutionException("connect event", channel, getClass() + "error when process connected event .", t);
        }
    }

    @Override
    public void disconnected(Channel channel) throws RemotingException {
        try {checkQueueLength();
            connectionExecutor.execute(new ChannelEventRunnable(channel, handler, ChannelState.DISCONNECTED));
        } catch (Throwable t) {throw new ExecutionException("disconnected event", channel, getClass() + "error when process disconnected event .", t);
        }
    }

    @Override
    public void received(Channel channel, Object message) throws RemotingException {ExecutorService executor = getExecutorService();
        try {executor.execute(new ChannelEventRunnable(channel, handler, ChannelState.RECEIVED, message));
        } catch (Throwable t) {
            //fix, reject exception can not be sent to consumer because thread pool is full, resulting in consumers waiting till timeout.
            if (message instanceof Request && t instanceof RejectedExecutionException) {Request request = (Request) message;
                if (request.isTwoWay()) {String msg = "Server side(" + url.getIp() + "," + url.getPort() + ") threadpool is exhausted ,detail msg:" + t.getMessage();
                    Response response = new Response(request.getId(), request.getVersion());
                    response.setStatus(Response.SERVER_THREADPOOL_EXHAUSTED_ERROR);
                    response.setErrorMessage(msg);
                    channel.send(response);
                    return;
                }
            }
            throw new ExecutionException(message, channel, getClass() + "error when process received event .", t);
        }
    }

    @Override
    public void caught(Channel channel, Throwable exception) throws RemotingException {ExecutorService executor = getExecutorService();
        try {executor.execute(new ChannelEventRunnable(channel, handler, ChannelState.CAUGHT, exception));
        } catch (Throwable t) {throw new ExecutionException("caught event", channel, getClass() + "error when process caught event .", t);
        }
    }

    private void checkQueueLength() {if (connectionExecutor.getQueue().size() > queuewarninglimit) {logger.warn(new IllegalThreadStateException("connectionordered channel handler `queue size:" + connectionExecutor.getQueue().size() + "exceed the warning limit number :" + queuewarninglimit));
        }
    }
}

• ConnectionOrderedChannelHandler 继承了 WrappedChannelHandler，其构造器创建了 corePoolSize 及 maximumPoolSize 均为 1，queue 为 LinkedBlockingQueue 的 connectionExecutor
• 其 connected、disconnected 方法均是使用 connectionExecutor 来执行新创建的 ChannelEventRunnable；这两个方法均会先执行 checkQueueLength 来判断 queue 大小是否大于 queuewarninglimit，大于的话则打印 warn 日志
• 其 received、caught 均是通过父类的 getExecutorService 获取线程池，然后执行创建的 ChannelEventRunnable；received 方法在捕获到异常时 RejectedExecutionException 且 message 是 Request，而且 request 是 twoWay 的时候会返回 SERVER_THREADPOOL_EXHAUSTED_ERROR

ConnectChannelHandlerTest

dubbo-2.7.3/dubbo-remoting/dubbo-remoting-api/src/test/java/org/apache/dubbo/remoting/handler/ConnectChannelHandlerTest.java

public class ConnectChannelHandlerTest extends WrappedChannelHandlerTest {

    @BeforeEach
    public void setUp() throws Exception {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(true), url);
    }

    @Test
    public void test_Connect_Blocked() throws RemotingException {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(false), url);
        ThreadPoolExecutor executor = (ThreadPoolExecutor) getField(handler, "connectionExecutor", 1);
        Assertions.assertEquals(1, executor.getMaximumPoolSize());

        int runs = 20;
        int taskCount = runs * 2;
        for (int i = 0; i < runs; i++) {handler.connected(new MockedChannel());
            handler.disconnected(new MockedChannel());
            Assertions.assertTrue(executor.getActiveCount() <= 1, executor.getActiveCount() + "must <=1");
        }
        //queue.size 
        Assertions.assertEquals(taskCount - 1, executor.getQueue().size());

        for (int i = 0; i < taskCount; i++) {if (executor.getCompletedTaskCount() < taskCount) {sleep(100);
            }
        }
        Assertions.assertEquals(taskCount, executor.getCompletedTaskCount());
    }

    @Test //biz error should not throw and affect biz thread.
    public void test_Connect_Biz_Error() throws RemotingException {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(true), url);
        handler.connected(new MockedChannel());
    }

    @Test //biz error should not throw and affect biz thread.
    public void test_Disconnect_Biz_Error() throws RemotingException {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(true), url);
        handler.disconnected(new MockedChannel());
    }

    @Test
    public void test_Connect_Execute_Error() throws RemotingException {Assertions.assertThrows(ExecutionException.class, () -> {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(false), url);
            ThreadPoolExecutor executor = (ThreadPoolExecutor) getField(handler, "connectionExecutor", 1);
            executor.shutdown();
            handler.connected(new MockedChannel());
        });
    }

    @Test
    public void test_Disconnect_Execute_Error() throws RemotingException {Assertions.assertThrows(ExecutionException.class, () -> {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(false), url);
            ThreadPoolExecutor executor = (ThreadPoolExecutor) getField(handler, "connectionExecutor", 1);
            executor.shutdown();
            handler.disconnected(new MockedChannel());
        });
    }

    //throw  ChannelEventRunnable.runtimeExeception(int logger) not in execute exception
    @Test//(expected = RemotingException.class)
    public void test_MessageReceived_Biz_Error() throws RemotingException {handler.received(new MockedChannel(), "");
    }

    //throw  ChannelEventRunnable.runtimeExeception(int logger) not in execute exception
    @Test
    public void test_Caught_Biz_Error() throws RemotingException {handler.caught(new MockedChannel(), new BizException());
    }

    @Test
    public void test_Received_InvokeInExecuter() throws RemotingException {Assertions.assertThrows(ExecutionException.class, () -> {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(false), url);
            ThreadPoolExecutor executor = (ThreadPoolExecutor) getField(handler, "SHARED_EXECUTOR", 1);
            executor.shutdown();
            executor = (ThreadPoolExecutor) getField(handler, "executor", 1);
            executor.shutdown();
            handler.received(new MockedChannel(), "");
        });
    }

    /**
     * Events do not pass through the thread pool and execute directly on the IO
     */
    @SuppressWarnings("deprecation")
    @Disabled("Heartbeat is processed in HeartbeatHandler not WrappedChannelHandler.")
    @Test
    public void test_Received_Event_invoke_direct() throws RemotingException {handler = new ConnectionOrderedChannelHandler(new BizChannelHander(false), url);
        ThreadPoolExecutor executor = (ThreadPoolExecutor) getField(handler, "SHARED_EXECUTOR", 1);
        executor.shutdown();
        executor = (ThreadPoolExecutor) getField(handler, "executor", 1);
        executor.shutdown();
        Request req = new Request();
        req.setHeartbeat(true);
        final AtomicInteger count = new AtomicInteger(0);
        handler.received(new MockedChannel() {
            @Override
            public void send(Object message) throws RemotingException {Assertions.assertTrue(((Response) message).isHeartbeat(), "response.heartbeat");
                count.incrementAndGet();}
        }, req);
        Assertions.assertEquals(1, count.get(), "channel.send must be invoke");
    }
}

• ConnectChannelHandlerTest 在 setup 时创建的是 ConnectionOrderedChannelHandler，然后进行了 test_Connect_Blocked、test_Connect_Biz_Error、test_Disconnect_Biz_Error、test_Connect_Execute_Error、test_Disconnect_Execute_Error、test_MessageReceived_Biz_Error、test_Caught_Biz_Error、test_Received_InvokeInExecuter、test_Received_Event_invoke_direct

小结

• ConnectionOrderedDispatcher 实现了 Dispatcher 接口，其 dispatch 方法返回的是 ConnectionOrderedChannelHandler；ConnectionOrderedChannelHandler 继承了 WrappedChannelHandler，其构造器创建了 corePoolSize 及 maximumPoolSize 均为 1，queue 为 LinkedBlockingQueue 的 connectionExecutor
• ConnectionOrderedChannelHandler 的 connected、disconnected 方法均是使用 connectionExecutor 来执行新创建的 ChannelEventRunnable；这两个方法均会先执行 checkQueueLength 来判断 queue 大小是否大于 queuewarninglimit，大于的话则打印 warn 日志
• ConnectionOrderedChannelHandler 的 received、caught 均是通过父类的 getExecutorService 获取线程池，然后执行创建的 ChannelEventRunnable；received 方法在捕获到异常时 RejectedExecutionException 且 message 是 Request，而且 request 是 twoWay 的时候会返回 SERVER_THREADPOOL_EXHAUSTED_ERROR

doc

• ConnectionOrderedDispatcher