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@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 

ColdBox Platform: http://www.coldbox.org 


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