Re: t5559 breaks with apache 2.4.55

[Jeff King <peff@peff.net>]

On Thu, Jan 26, 2023 at 06:39:42AM -0500, Jeff King wrote:

> Yeah, after seeing that, I'm quite sure this is a mod_http2 issue. It
> would be nice to bisect within the mod_http2 history to find the
> culprit, but I'd first have to figure out how to build standalone apache
> modules. ;)

This turned out to be quite painless, so I bisected using the source at:

  https://github.com/icing/mod_h2

Unfortunately, it's not super helpful for identifying the problem.  The
culprit turns out to be 16ffed9692b, which has a 450-line diff. The
commit message is:

  * refactored stream response handling to reflect the different phases
    (response/data/trailers) more clearly and help resolving cpu busy loops.

But that does at least give me more confidence that the bug is in
mod_http2, and isn't, say, some intentional behavior change there that
happens to trigger a bug in curl.

I opened an issue here: https://github.com/icing/mod_h2/issues/243

So we'll see if that helps.

I re-read your earlier thread, and the version problems you have don't
quite line up. I think you were having issues with mod_http2 2.0.9, but
the older version (1.5.19) worked. I was OK with 2.0.9, but upgrading to
2.0.10 broke things. I'd hate to have to disable t5559 by default; it
does catch some cases that would trigger in the real-world (since real
sites like GitHub are using http2). But if it's too unreliable in
practice, that might be the path of least resistance.

-Peff