[undertow-dev] Response stream not auto closing for content length 0

[Stuart Douglas]

I guess you could argue that this is a bug, but really you should not be
calling write() with a zero length byte array. You can file an issue if you
want but I am not really sure if this is something we want to fix.

Stuart

On Wed, Jun 12, 2019 at 2:19 AM Jonas Konrad <me at yawk.at> wrote:

> Hey,
>
> I was working on a web server implemented with undertow and came across
> a weird inconsistency. When setting the response content length of an
> exchange and then writing to its output stream, normally the output
> self-closes as soon as the proper content length is hit. However, it
> turns out that this does not happen when content length is zero. This
> leads to the response remaining open if you've previously dispatch()ed it.
>
> The code in question is here:
>
> https://github.com/yawkat/aggressive-cache/blob/fcd59ef0d35d8cd6102eceed103f93e073507378/src/main/java/at/yawk/aggressivecache/CacheHandler.java#L70
> - the relevant bit goes as follows:
>
> exchange.startBlocking();
> exchange.dispatch();
> ... later ...
> exchange.setResponseContentLength(body.length);
> exchange.getOutputStream().write(r.body);
>
> (I'm aware that I should avoid no-arg dispatch, and that I should be
> closing the output stream - this was a rushed side project)
>
> I've tracked down the issue to this class:
>
> https://github.com/undertow-io/undertow/blob/master/core/src/main/java/io/undertow/io/UndertowOutputStream.java
>
> Normally, updateWritten(long) checks whether the content length has been
> reached and if so, closes the stream and writes the response. However,
> when passing an empty array to write(byte[], int, int), we run into a
> length check and updateWritten is never executed, and thus the stream is
> never closed.
>
> Is this a bug? I know the issue came from me using undertow improperly,
> but it certainly is inconsistent. To me it seems like the idea here is
> to close the stream when the response is done, which does not happen
> when writing a 0-length array. However it could also be argued that
> outputstream.write(new byte[0]) should never do anything.
>
> If this is a bug, I'll happily make an issue and a PR for it if that's
> better for you - it doesn't look like it's that much work.
>
> Thank you,
> - Jonas
> _______________________________________________
> undertow-dev mailing list
> undertow-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/undertow-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/undertow-dev/attachments/20190612/da03559b/attachment.html