Re: [jetty-users] Is static ConcurrentHashMap a reliable choice for WebSocketServlet?
Hi Lachlan, thank you for your comments! Over the weekend I have rewritten the custom WebSocketListener in my little word game to have a static ConcurrentHashMap of ConcurrentHashMaps with the outer key being user ids and with the inner keys being strings made of session.getRemoteAddress().getHostString() + ":" + session.getRemoteAddress().getPort() - because they identify the multiple Sessions for a user (when she/he uses several browser tabs or maybe uses desktop and mobile versions at the same time): https://gist.github.com/afarber/4f82205881ddb0223130f74b4e87abda And yes, I had also the structure in the servlet before and passed it by a custom WebSocketCreator. Both variants work and of course Jetty has only 1 process (I can see it on my Linux machine). At the same I have followed Joakim's advice and decreased the idle timeout to 5 minutes. And additionally I track when there is no human actions at the remote end for 5 minutes - and close those sessions at my servlet (to handle the abandoned browser tabs). I didn't have to use ping in my code... I have impression that Jetty source code is very stable and overall excellent, thank you Sorry if my mail was a bit offtopic Best regards Alex ___ jetty-users mailing list jetty-users@eclipse.org To unsubscribe from this list, visit https://www.eclipse.org/mailman/listinfo/jetty-users
Re: [jetty-users] Is static ConcurrentHashMap a reliable choice for WebSocketServlet?
Alexander,
I think the ConcurrentHashMap data structure is fine. However it doesn't
necessarily need to be static. You could store it as a field in your
WebSocketServlet and pass it in when you create your WebSocketListener.
In your code I would only expect oldSession to be non-null when you have
multiple connections for the same mUid. The standard case where you have no
previous entry in the map for mUid, then the value returned by
`SESSIONS.put(mUid, mSession)` will be null.
Cheers,
Lachlan
On Sun, Feb 28, 2021 at 9:05 AM Alexander Farber
wrote:
> Good evening,
>
> In a custom WebSocketServlet in Jetty 9.4.37.v20210219 I would like to
> maintain Session objects in a shared data structure.
>
> Is a static data structure like
>
> public final static Map SESSIONS = new
> ConcurrentHashMap<>();
>
> a good choice for that?
>
> I have a feeling it does not work reliably. Maybe Jetty starts several
> Linux process and thus the static data structure is not shared among them?
>
> Because in my custom WebSocketListener I have a code:
>
> @Override
> public void onWebSocketText(String str) {
> // here the user is authenticated and mUid is found
> Session oldSession = SESSIONS.put(mUid, mSession);
> disconnect(oldSession);
> }
>
> private void disconnect(Session session) {
> LOG.info("disconnect: session={}", session); // surprisingly often
> session is null
> try {
> session.close();
> session.disconnect();
> } catch (Exception ex) {
> // ignore
> }
> }
>
> And often the old session printed by the above LOG is null, even though I
> would expect it be non-null.
>
> Best regards
> Alex
>
> ___
> jetty-users mailing list
> jetty-users@eclipse.org
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> https://www.eclipse.org/mailman/listinfo/jetty-users
>
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[jetty-users] Is static ConcurrentHashMap a reliable choice for WebSocketServlet?
Good evening,
In a custom WebSocketServlet in Jetty 9.4.37.v20210219 I would like to
maintain Session objects in a shared data structure.
Is a static data structure like
public final static Map SESSIONS = new
ConcurrentHashMap<>();
a good choice for that?
I have a feeling it does not work reliably. Maybe Jetty starts several
Linux process and thus the static data structure is not shared among them?
Because in my custom WebSocketListener I have a code:
@Override
public void onWebSocketText(String str) {
// here the user is authenticated and mUid is found
Session oldSession = SESSIONS.put(mUid, mSession);
disconnect(oldSession);
}
private void disconnect(Session session) {
LOG.info("disconnect: session={}", session); // surprisingly often
session is null
try {
session.close();
session.disconnect();
} catch (Exception ex) {
// ignore
}
}
And often the old session printed by the above LOG is null, even though I
would expect it be non-null.
Best regards
Alex
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