WebKit bots having too many TIME_WAIT sockets

[youennf]

As shown in https://bugs.webkit.org/show_bug.cgi?id=159166#c21, some WebKit bots WPT servers (localhost-running) may have too many sockets in the TIME_WAIT state. This seems to prevent running the tests correctly for some runs.

Has anybody encountered the issue?
Maybe keep-alive should be implemented in wptserve to reduce the risk?

[youennf]

Looking at the code, it seems keep-alive is in action.
Not sure why we are seeing so much TIME_WAIT sockets then.

[youennf]

It might be that mote responses have no content-length header

[gsnedders]

I spent a few hours last week trying to work out why under high load wptserve seems to sometimes hang, using ab—on OS X, it consistently stopped responding at c.16500, with all connections after that getting stuck in SYN_SENT. I didn't really get anywhere very useful, though! May well be related, though?

In principle, any response without Content-Length should have the connection closed by the server after the end of the response. If that's not true, we should fix that.

[youennf]

If more responses had content-length headers, we would enable a lot more reuse of sockets.
I am trying to check whether https://github.com/youennf/wptserve/tree/webkit-current-wptserver would reduce the issue.

[gsnedders]

I have some memory of @jgraham or @Ms2ger having some reason why #86 didn't get merged.

That said, we shouldn't have them stuck in TIME_WAIT even without socket reuse.

[gsnedders]

We've also had issues with w3c-test.org sometimes stopping responding, so I suspect there might be some underlying issue regardless.

[gsnedders]

FWIW, I tried to look into why this happened and I couldn't figure out why it stopped working at the specific point it did looking at DTrace. That said, I've never tried to deal with anything at this level on OS X previously. Equally, I couldn't reproduce it on Linux artificially limiting number of sockets.

[wpt-issue-mover]

This issue has been moved to web-platform-tests/wpt#8369; please continue all discussion there.