Please see below:
On 9/29/12 5:16 PM, Sven Jacobs wrote:
> Ok, I have the following problem:
>
> Let's say we have two REST resources /objects and /notifications.
> /notifications is a WebSocket resource provided by the Atmosphere
> framework.
> Let's say a client POSTs to /objects to create a new resource.
>
> Pseudocode
>
> @Path("/objects")
> class Objects {
> @POST
> public Response create() {
> long rev = nextRevision();
> SomeObject obj = new SomeObject(rev);
> return Response.created(...).entity(obj).build();
> }
> }
>
> nextRevision() increases the global revision number and fires an
> internal event. The /notifications resource listens for the event and
> sends a WebSocket message to all connected clients saying "Hey, I have
> a new object resource with revision x".
> The problem here is that the WebSocket notification is send before the
> client received the response from the /objects POST request. So what
> I'd like to do is put the code which fires the internal revision event
> at a place where I'm certain that the client first received the POST
> response from /objects.
It seems to me even the notification you are asking for might not be
sufficient in your case. Since server can only know that it sent all the
data, that by itself does not mean the client processed them. I.e. even
if there was an event you could listen to, you would receive it after
the data has been sent to the client, not necessarily after the client
processed them - and since this is happening on different threads, in
theory the client could still receive the websocket message earlier than
it processes the response to the POST message from the server.
So you may need to approach it differently anyway. E.g. by synchronizing
these things (sending the post request and processing of the web socket
messages) on the client side.
Martin