On Thu, 28 Feb 2019 at 21:29, Austin Bookhart <
austin.bookh...@hannonhill.com> wrote:
> Hi,
>
> I have a question regarding an asynchronous websocket implementation
> we have in our application. We have run into issues where on a rare
> occasion the websocket endpoint will become unusable due to what seems
> to be a thread holding onto resources and not releasing them. Below is
> the main structure of our endpoint. Some parts have been removed or
> commented out, but it gets the basic structure across.
>
> We call "sendMessageToUser" in order to send a message to a client's
> browser. The issue that we have seen is if we breakpoint at the line
> that waits for the future to resolve, "future.get()", and reload the
> current client's browser, the endpoint becomes unusable where no
>
The code below is very weird code to me, but i guess this is just to show
it?
Because if i look at the doc of the Async.sendText()
Then the get() of the Future should throw an exception on connections
errors.
But in your case it just never resolves?
> messages can be sent or received any longer. Only a restart resolves
> the issue. We wanted to find out if our implementation of the
> asynchronous remote and future setup is correct or if there is a more
> appropriate use of the API?
>
> Appreciate any help you can provide.
> Thanks,
> Austin
>
> @ServerEndpoint(value = "/websocket", configurator =
> GetHttpSessionConfigurator.class)
> public class WebSocketEndpoint
> {
> private static final Map<Session, SessionDetails> clients =
> Collections.synchronizedMap(new HashMap<Session, SessionDetails>());
> private static Future<Void> future = null;
>
> public static void sendMessageToUser(String username,
> WebSocketMessage message)
> {
> synchronized (clients)
> {
> clients.keySet().stream()
> .filter(client ->
> username.equals(clients.get(client).username))
> .forEach(client -> sendMessage(client, message));
> }
> }
>
> private static synchronized void sendMessage(Session client,
> WebSocketMessage message)
> {
> try
> {
> if (future == null)
> LOG.debug("Sending very first WebSocket message");
> else
> {
> // Before we send the next message, we have to wait
> for the previous message to complete
> LOG.debug("Waiting until last WebSocket message is being
> sent");
> future.get();
>
> LOG.debug("Last WebSocket message is not longer being
> sent. Sending a new message.");
> }
>
>
> // Send the message and store the Future for the next call
> future =
> client.getAsyncRemote().sendText(message.getJSONObject().toString());
> }
> catch (Exception e)
> {
> LOG.debug("An error occurred when sending a web socket
> message to client " + client, e);
> }
> }
>
> @OnOpen
> public void onOpen(Session client, EndpointConfig config)
> {
> //Construct SessionDetails information
> clients.put(client, new SessionDetails(..));
> }
>
> @OnClose
> public void onClose(Session client)
> {
> clients.remove(client);
> }
> }
>
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>
--
Johan Compagner
Servoy
