[undertow-dev] Unexpected RequestLimitingHandler behavior after queue gets full

[Piotr Betkier]

Awesome, thanks!

Piotr

On Thu Dec 04 2014 at 3:06:07 AM Stuart Douglas <sdouglas at redhat.com> wrote:

> I created a JIRA:
>
> https://issues.jboss.org/browse/UNDERTOW-349
>
> Fix is upstream, will be in release of 1.1.2.Final and 1.2.0.Beta7.
>
> Stuart
>
> ----- Original Message -----
> > From: "Piotr Betkier" <pbetkier at gmail.com>
> > To: undertow-dev at lists.jboss.org
> > Sent: Thursday, 4 December, 2014 9:12:25 AM
> > Subject: [undertow-dev] Unexpected RequestLimitingHandler behavior
> after      queue gets full
> >
> > Hello,
> >
> > I wanted to introduce a constraint on the number of requests my server
> tries
> > to handle at a time and played around with RequestLimitingHandler a
> little
> > bit. However, I observed unexpected behavior once RequestLimit's queue
> gets
> > full.
> >
> > I've created a RequestLimitingHandler with both
> maximumConcurrentRequests and
> > queueSize set to 1 and nextHandler that responds after a 3 second sleep.
> > This is what I observed:
> >
> > When I sent 2 concurrent requests with a curl, I got the first response
> after
> > 3 seconds and the second one after 6 - just as expected, the second
> request
> > got queued.
> >
> > When I sent 3 concurrent requests, I got two correct responses and one
> 513 -
> > just as expected, my third request couldn't fit into the queue so a
> failure
> > handler got called.
> >
> > Now it got tricky - this made RequestLimit enter an invalid state, where
> its
> > "state" field got decremented below the value that represents 0 current
> > requests. Now "state & MASK_CURRENT" gives 2147483647 instead of 0, so
> the
> > next time I make a single request, RequestLimit thinks there are
> 2147483647
> > requests in the system currently and queues my request instead of
> handling
> > it. Then I make yet another request and now the queue is full, so 513
> error
> > is generated instantly which in turn makes RequestLimit poll my first
> > pending request from the queue and dispatch it for handling. RequestLimit
> > got corrupted and is unusable from now on.
> >
> > I hope I explained my observations clearly. Is there something wrong in
> my
> > setup, my understanding of Undertow or it's a bug? This is my code
> snippet,
> > tested with undertow 1.1.0.Final and 1.2.0.Beta5:
> >
> > import io.undertow.Undertow;
> > import io.undertow.server.HttpHandler;
> > import io.undertow.server.HttpServerExchange;
> > import io.undertow.server.handlers.RequestLimitingHandler;
> > import io.undertow.util.Headers;
> >
> > public class Main {
> >
> > public static void main(String[] args) {
> > Undertow server = Undertow.builder()
> > .addHttpListener(8080, "localhost")
> > .setHandler(new RequestLimitingHandler(1, 1, handler()))
> > .build();
> >
> > server.start();
> > }
> >
> > private static HttpHandler handler() {
> > return new HttpHandler() {
> > @Override
> > public void handleRequest(final HttpServerExchange exchange) throws
> Exception
> > {
> > Thread.sleep(3000);
> > exchange.getResponseHeaders().put(Headers.CONTENT_TYPE, "text/plain");
> > exchange.getResponseSender().send("Hello World");
> > }
> > };
> > }
> >
> > }
> >
> >
> > Cheers,
> > Piotr
> >
> >
> > _______________________________________________
> > undertow-dev mailing list
> > undertow-dev at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/undertow-dev
>
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