虚拟机vnc端口切换时如何让guacamole切换端口重试连接

虚拟机vnc默认端口是5901，如果虚拟机不属于正常关闭，文件/tmp/.X11-unix/X1不会被删除，当虚拟机启动的时候不会使用5901端口启动vnc server服务，而是启用5902端口（如果文件/tmp/.X11-unix/X2也存在则使用5903端口，依次类推）。



建立到guacamole代理服务器的tunnel时候需要带上vnc的连接信息，如果guacd连接目标虚拟机出错时不会抛出Exception，所以我们的代码没有办法捕获异常去换端口重试连接。

解决方案是重载GuacamoleHTTPTunnelServlet的doRead方法，通过读取webserver发出connect请求之后的第一个流数据，分析里面是否包含错误信息，如果有则重新创建一个tunnel（要拿到旧tunnel的uuid，所有的tunnel都放到map里面缓存的，key就是uuid），然后注册新的tunnel。

@Override
protected void doRead(HttpServletRequest request, HttpServletResponse response, String tunnelUUID)
throws GuacamoleException {

// Get tunnel, ensure tunnel exists
GuacamoleTunnel tunnel = getTunnel(tunnelUUID);

// Ensure tunnel is open
if (!tunnel.isOpen())
throw new GuacamoleResourceNotFoundException("Tunnel is closed.");

// Obtain exclusive read access
GuacamoleReader reader = tunnel.acquireReader();

try {

// Note that although we are sending text, Webkit browsers will
// buffer 1024 bytes before starting a normal stream if we use
// anything but application/octet-stream.
response.setContentType("application/octet-stream");
response.setHeader("Cache-Control", "no-cache");

// Get writer for response
Writer out = new BufferedWriter(new OutputStreamWriter(response.getOutputStream(), "UTF-8"));

// Stream data to response, ensuring output stream is closed
try {

// Deregister tunnel and throw error if we reach EOF without
// having ever sent any data
char[] message = reader.read();
if (message == null)
throw new GuacamoleConnectionClosedException("Tunnel reached end of stream.");
// 这里是我添加的代码--begin
// guacd server error
if (new String(message).contains("3.519")) {
rebuildTunnel(request, response, tunnelUUID, tunnel);
}
// 这里是我添加的代码--end

// For all messages, until another stream is ready (we send at
// least one message)
do {

// Get message output bytes
out.write(message, 0, message.length);

// Flush if we expect to wait
if (!reader.available()) {
out.flush();
response.flushBuffer();
}

// No more messages another stream can take over
if (tunnel.hasQueuedReaderThreads())
break;

} while (tunnel.isOpen() && (message = reader.read()) != null);

// Close tunnel immediately upon EOF
if (message == null) {
deregisterTunnel(tunnel);
tunnel.close();
}

// End-of-instructions marker
out.write("0.;");
out.flush();
response.flushBuffer();
}

// Send end-of-stream marker and close tunnel if connection is
// closed
catch (GuacamoleConnectionClosedException e) {
// Deregister and close
deregisterTunnel(tunnel);
tunnel.close();

// End-of-instructions marker
out.write("0.;");
out.flush();
response.flushBuffer();

}

catch (GuacamoleException e) {

// Deregister and close
deregisterTunnel(tunnel);
tunnel.close();
throw e;
}

// Always close output stream
finally {
out.close();
}

} catch (IOException e) {

// Log typically frequent I/O error if desired
log.debug("Error writing to servlet output stream", e);

// Deregister and close
deregisterTunnel(tunnel);
tunnel.close();

} finally {
tunnel.releaseReader();
}

}

private void rebuildTunnel(HttpServletRequest request, HttpServletResponse response, String tunnelUUID,
GuacamoleTunnel tunnel) throws GuacamoleException {
GuacamoleSocket socket = tunnel.getSocket();
GuacamoleConfiguration configuration = ((ConfiguredGuacamoleSocket) socket).getConfiguration();
if ("vnc".equalsIgnoreCase(configuration.getProtocol())) {
int port = Integer.parseInt(configuration.getParameter("port"));
log.warn(String.format("vnc service with [%s:%d] not work, increasing port and retry",
configuration.getParameter("hostname"), port));
if (port++ < 5910) {
configuration.setParameter("port", port + "");
deregisterTunnel(tunnel);
tunnel.close();
// TODO get cloud providerId
tunnel = new GuacamoleVncReconnectTunnel(
new ConfiguredGuacamoleSocket(getSocket(""), configuration), tunnelUUID);
registerTunnel(tunnel);
doRead(request, response, tunnelUUID);
}
}
}