A way to flush/deliver messages before disconnecting

Hey folks,

We are currently sending some messages, and based on a flag disconnect the clients if the conversation/process is finished. If so, we call client.disconnect() on it to make sure the client no longer keeps the connection open.

However, this is causing client to disconnect even before receiving the messages. I was hoping to have a client.disconnect(flushBeforeDisconnectBoolean) or a simple method as client.flush that sends all messages by blocking the call.

Is there a way to send messages and then wait for it to be delivered before disconnecting the client ?

[sbordet]

@jaypatel512 this is already possible in CometD 4:

serverChannel.publish(null, data, Promise.complete((r, x) -> serverSession.disconnect()));

If you like Java’s CompletableFuture, use Promise.Completable (a subclass of Java’s CompletableFuture):

Promise.Completable<Boolean> completable = new Promise.Completable<>();
serverSession.deliver(null, "/channel", data, completable);
completable.thenAccept(b -> serverSession.disconnect());

[sbordet]

You have to clarify what you mean exactly by “disconnect”. CometD disconnect message? TCP disconnect?

The server side promise cannot wait for the browser. The server side promise is completed as soon as the TCP write succeeds (or fails). Whether the message will arrive to the client, that is unknown to the server, and the server cannot wait. It may still happen, however, that the messages and the disconnect message (from server to client) travel onto 2 different TCP connections and therefore there is no guarantee of ordering between the messages and the disconnect message.

The ack extension guarantees ordered delivery.