How does the HeartBeat work?

[mxf <91...@qq.com>]

Hello，There's a question I'd like to ask about apache-sshd keealive.


The sshclient only send keepAlive every interal time,but not to check the reply of the keepAlive timeout.
> how does the client know that the server is available.
> Or does other param need to set to make the client heartbeat work?



what param of ssh client I set is :
I just set the HEARTBEAT_INTERVAL(20 senconds) and the IDLE_TIMEOUT(300senconds), the NIO_READ_TIMEOUT(315seconds).Does other param need to set to make the heartbeat available?


related code i understand is: 
 protected void startHeartBeat() {
        ClientSession session = getClientSession();
        long interval = session.getLongProperty(ClientFactoryManager.HEARTBEAT_INTERVAL, ClientFactoryManager.DEFAULT_HEARTBEAT_INTERVAL);
        if (interval > 0L) {
            FactoryManager manager = session.getFactoryManager();
            ScheduledExecutorService service = manager.getScheduledExecutorService();
            service.scheduleAtFixedRate(this::sendHeartBeat, interval, interval, TimeUnit.MILLISECONDS);
            if (log.isDebugEnabled()) {
                log.debug("startHeartbeat - started at interval={}", interval);
            }
        }
    }
 
    /**
     * Sends a heartbeat message
     * @return The {@link IoWriteFuture} that can be used to wait for the
     * message write completion
     */
    protected IoWriteFuture sendHeartBeat() {
        ClientSession session = getClientSession();
        String request = session.getStringProperty(ClientFactoryManager.HEARTBEAT_REQUEST, ClientFactoryManager.DEFAULT_KEEP_ALIVE_HEARTBEAT_STRING);
        try {
            Buffer buf = session.createBuffer(SshConstants.SSH_MSG_GLOBAL_REQUEST, request.length() + Byte.SIZE);
            buf.putString(request);
            buf.putBoolean(false);
            return session.writePacket(buf);
        } catch (IOException e) {
            if (log.isDebugEnabled()) {
                log.debug("Error (" + e.getClass().getSimpleName() + ") sending keepalive message=" + request + ": " + e.getMessage());
            }
 
            Throwable t = e;
            return new AbstractIoWriteFuture(request, null) {
                {
                    setValue(t);
                }
            };
        }
    }

Re: How does the HeartBeat work?

[elijah baley <e_...@outlook.com>]

You don't even have to set these parameters - there are some defaults that are used anyway (unless you override them). The recommendation is to intervene only if the defaults are not compatible with your needs and/or to disable the features


________________________________
From: mxf <91...@qq.com>
Sent: Sunday, October 22, 2017 5:44 PM
To: dev
Subject: How does the HeartBeat work?

Hello，There's a question I'd like to ask about apache-sshd keealive.


The sshclient only send keepAlive every interal time,but not to check the reply of the keepAlive timeout.
> how does the client know that the server is available.
> Or does other param need to set to make the client heartbeat work?



what param of ssh client I set is :
I just set the HEARTBEAT_INTERVAL(20 senconds) and the IDLE_TIMEOUT(300senconds), the NIO_READ_TIMEOUT(315seconds).Does other param need to set to make the heartbeat available?


related code i understand is:
 protected void startHeartBeat() {
        ClientSession session = getClientSession();
        long interval = session.getLongProperty(ClientFactoryManager.HEARTBEAT_INTERVAL, ClientFactoryManager.DEFAULT_HEARTBEAT_INTERVAL);
        if (interval > 0L) {
            FactoryManager manager = session.getFactoryManager();
            ScheduledExecutorService service = manager.getScheduledExecutorService();
            service.scheduleAtFixedRate(this::sendHeartBeat, interval, interval, TimeUnit.MILLISECONDS);
            if (log.isDebugEnabled()) {
                log.debug("startHeartbeat - started at interval={}", interval);
            }
        }
    }

    /**
     * Sends a heartbeat message
     * @return The {@link IoWriteFuture} that can be used to wait for the
     * message write completion
     */
    protected IoWriteFuture sendHeartBeat() {
        ClientSession session = getClientSession();
        String request = session.getStringProperty(ClientFactoryManager.HEARTBEAT_REQUEST, ClientFactoryManager.DEFAULT_KEEP_ALIVE_HEARTBEAT_STRING);
        try {
            Buffer buf = session.createBuffer(SshConstants.SSH_MSG_GLOBAL_REQUEST, request.length() + Byte.SIZE);
            buf.putString(request);
            buf.putBoolean(false);
            return session.writePacket(buf);
        } catch (IOException e) {
            if (log.isDebugEnabled()) {
                log.debug("Error (" + e.getClass().getSimpleName() + ") sending keepalive message=" + request + ": " + e.getMessage());
            }

            Throwable t = e;
            return new AbstractIoWriteFuture(request, null) {
                {
                    setValue(t);
                }
            };
        }
    }