Tomcat出现假死原因及解决方法

//NioEndpoint$Acceptor#run
protected class Acceptor extends AbstractEndpoint.Acceptor {
    @Override
    public void run() {
        int errorDelay = 0;
        // Loop until we receive a shutdown command
        while (running) {
            //...忽略一些代码
            state = AcceptorState.RUNNING;
            try {
                //if we have reached max connections, wait
                countUpOrAwaitConnection();
                SocketChannel socket = null;
                try {
                    socket = serverSock.accept();
                } catch (IOException ioe) {
                }
                // Successful accept, reset the error delay
                errorDelay = 0;
                // Configure the socket
                if (running && !paused) {
                    // setSocketOptions() will hand the socket off to
                    // an appropriate processor if successful
                    if (!setSocketOptions(socket)) {
                        closeSocket(socket);
                    }
                } else {
                    closeSocket(socket);
                }
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
                log.error(sm.getString("endpoint.accept.fail"), t);
            }
        }
        state = AcceptorState.ENDED;
    }
	//...忽略一些代码
}

//NioEndpoint#setSocketOptions
protected boolean setSocketOptions(SocketChannel socket) {
    // Process the connection
    try {
        //disable blocking, APR style, we are gonna be polling it
        socket.configureBlocking(false);
        Socket sock = socket.socket();
        socketProperties.setProperties(sock);

        NioChannel channel = nioChannels.pop();
        if (channel == null) {
            SocketBufferHandler bufhandler = new SocketBufferHandler(
                    socketProperties.getAppReadBufSize(),
                    socketProperties.getAppWriteBufSize(),
                    socketProperties.getDirectBuffer());
            if (isSSLEnabled()) {
                channel = new SecureNioChannel(socket, bufhandler, selectorPool, this);
            } else {
                channel = new NioChannel(socket, bufhandler);
            }
        } else {
            channel.setIOChannel(socket);
            channel.reset();
        }
        getPoller0().register(channel);
    } catch (Throwable t) {
        ExceptionUtils.handleThrowable(t);
        try {
            log.error("",t);
        } catch (Throwable tt) {
            ExceptionUtils.handleThrowable(tt);
        }
        // Tell to close the socket
        return false;
    }
    return true;
}

//ExceptionUtils#handleThrowable
public static void handleThrowable(Throwable t) {
    if (t instanceof ThreadDeath) {
        throw (ThreadDeath) t;
    }
    if (t instanceof StackOverflowError) {
        // Swallow silently - it should be recoverable
        return;
    }
    if (t instanceof VirtualMachineError) {
        throw (VirtualMachineError) t;
    }
    // All other instances of Throwable will be silently swallowed
}

//AbstractEndpoint#startAcceptorThreads
protected final void startAcceptorThreads() {
    int count = getAcceptorThreadCount();
    acceptors = new Acceptor[count];

    for (int i = 0; i < count; i++) {
        acceptors[i] = createAcceptor();
        String threadName = getName() + "-Acceptor-" + i;
        acceptors[i].setThreadName(threadName);
        Thread t = new Thread(acceptors[i], threadName);
        t.setPriority(getAcceptorThreadPriority());
        t.setDaemon(getDaemon());
        t.start();
    }
}

Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        logger.error("[Global Handler]thread-name:{},happen exp,", t.getName(), e);
    }
});

//NioEndpoint$Poller#events
public void run() {
    if (interestOps == OP_REGISTER) {
        try {
            socket.getIOChannel().register(
                    socket.getPoller().getSelector(), SelectionKey.OP_READ, socketWrapper);
        } catch (Exception x) {
            log.error(sm.getString("endpoint.nio.registerFail"), x);
        }
    }
    //...
}

//NioEndpoint$Poller#events
public boolean events() {
    boolean result = false;

    PollerEvent pe = null;
    for (int i = 0, size = events.size(); i < size && (pe = events.poll()) != null; i++ ) {
        result = true;
        try {
            pe.run();
            pe.reset();
            if (running && !paused) {
                eventCache.push(pe);
            }
        } catch ( Throwable x ) {
            log.error("",x);
        }
    }

    return result;
}

//NioEndpoint$Poller#run
public class Poller implements Runnable {
	public void run() {
		// Loop until destroy() is called
		while (true) {
			Boolean hasEvents = false;
			try {
				if (!close) {
					hasEvents = events();
					//....
				}
			}catch (Throwable x) {
				ExceptionUtils.handleThrowable(x);
				log.error("",x);
				continue;
			}
            //...
		}
	}
}