On Mon, 2016-12-12 at 21:15 +0000, Idzerda, Edan wrote:
> Hello! Our reverse proxy uses the Async Client pool to handle connections to
> backend servers. We've been tracking a problem for a while where we observe
> the initial TCP connection is made, but no thread is available to handle the
> SSL setup before a 10 second timeout expires. We get into trouble because
> some of our backend servers are very slow, and some of our clients download
> very slowly.
>
>
> I'm experimenting with a patch to AbstractMultiworkerIOReactor.addChannel()
> to determine whether the next dispatcher thread is "busy." My first try was
> to look at bufferedSessions from the BaseIOReactor, and go through the list
> of dispatchers one time to see if I can find a free one.
>
>
> int i = Math.abs(this.currentWorker++ % this.workerCount);
>
> for (int j = 0; j < this.workerCount; j++) {
>
> if (this.dispatchers[i].getSessionCount() == 0) {
>
> break;
>
> }
>
> i = Math.abs(this.currentWorker++ % this.workerCount);
>
> }
>
> this.dispatchers[i].addChannel(entry);
>
> This seems to help us in MOST of the cases we see this issue in production,
> but there still seem to be a small number of threads which collide. I'm
> testing a different version which looks at AbstractIOReactor "sessions" to
> determine thread busy state, but it never seems to show more than "1" session
> if I look at the size after piling up slow connections on top of each other.
>
> I have two questions:
> Is there a better way to determine whether a thread is busy?
> Would you be willing to accept a patch to make the dispatchers array in
> AbstractMultiworkerIOReactor "protected" so I can implement my own
> ConnectingIOReactor that overrides addChannel() with my own thread selection
> model?
>
> Thanks a lot for your help and for providing such a great library to the
> community!
>
> - edan
>
Hi Edan
What I do not quite understand is why i/o dispatch threads get blocked
for 10 seconds or longer. This sounds awfully suspicious.
I could imagine exposing the list of i/o dispatchers to subclasses of
AbstractMultiworkerIOReactor in 4.4.x branch but would rather prefer to
keep it as a last resort.
Oleg
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