[undertow-dev] Worker thread queue size and timeout behavior

[Bill O'Neil]

I'm not positive but I believe you need to look into the AcceptingChannel.
See the bound AcceptingChannel for HTTP here.
https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/Undertow.java#L192

Digging a little further you find NioXnioWorker.createTcpConnectionServer
https://github.com/xnio/xnio/blob/3.x/nio-impl/src/main/java/org/xnio/nio/NioXnioWorker.java#L177

Notice the backlog option. The Javadoc from ServerSocker.bind

* The {@code backlog} argument is the requested maximum number of
     * pending connections on the socket. Its exact semantics are
implementation
     * specific. In particular, an implementation may impose a maximum
length
     * or may choose to ignore the parameter altogther. The value provided
     * should be greater than {@code 0}. If it is less than or equal to
     * {@code 0}, then an implementation specific default will be used.
     * @param   endpoint        The IP address and port number to bind to.
     * @param   backlog         requested maximum length of the queue of
     *                          incoming connections.

So depending on the implementation it may or may not queue.

Then back to Undertow you can find
.set(Options.BACKLOG, 1000)
https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/Undertow.java#L138

So it defaults to a queue size of 1000 as long as the underlying
implementation supports it. You can configure it with the BACKLOG option.

Bill

On Thu, Feb 22, 2018 at 12:04 AM, Brad Wood <bdw429s at gmail.com> wrote:

> I'm looking for a bit of understanding on just how Undertow handles large
> numbers of requests coming into a server.  Specifically when more requests
> are being sent in than are being completed.  I've been doing some load
> testing on a CFML app (Lucee Server) where I happen to have my io-threads
> set to 4 and my worker-threads set to 150.  I'm using a monitoring tool
> (FusionReactor) that shows me the number of currently executing threads at
> my app and under heavy load I see exact 150 running HTTP threads in my app
> server, which makes sense since I have 150 worker threads.  I'm assuming
> here that I can't simultaneously process more requests than I have worker
> threads (please correct if I'm off there)
>
> So assuming I'm thinking that through correctly, what happens to
> additional requests that are coming into the server at that point?  I
> assume they are being queued somewhere, but
>
>    - What is this queue?
>    - How do I monitor it?
>    - How big can it get?
>    - Where do I change the size?
>    - How long do things stay in there before sending back an error to the
>    HTTP client?
>    - Can I control what error comes back to the HTTP client in that
>    scenario?
>    - If I'm using an HTTP/S and AJP listener, do they all share the same
>    settings?  Do they share the same queues?
>
> I've done a bit of Googling and reviewed some docs but haven't quite found
> any definitive information on this, and a lot of info I found was about
> Wildfly specifically so I wasn't sure how much of it applied.
>
> Thanks!
>
> ~Brad
>
> *Developer Advocate*
> *Ortus Solutions, Corp *
>
> E-mail: brad at coldbox.org
> ColdBox Platform: http://www.coldbox.org
> Blog: http://www.codersrevolution.com
>
>
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