Re: [PATCH] remote-curl: don't hang when a server dies before any output

From: Jeff King <peff@peff.net>
Date: Nov 15, 2016, 00:44 UTC
Message-ID: <20161115004426.unheihlmftlw6ex7@sigill.intra.peff.net>
In-Reply-To: <20161114194049.mktpsvgdhex2f4zv@sigill.intra.peff.net>

On Mon, Nov 14, 2016 at 02:40:49PM -0500, Jeff King wrote:

Show 21 quoted lines

> On Mon, Nov 14, 2016 at 01:24:31PM -0500, Jeff King wrote:
> 
> >   2. Have remote-curl understand enough of the protocol that it can
> >      abort rather than hang.
> > 
> >      I think that's effectively the approach of your patch, but for one
> >      specific case. But could we, for example, make sure that everything
> >      we proxy is a complete set of pktlines and ends with a flush? And
> >      if not, then we hang up on fetch-pack.
> > 
> >      I _think_ that would work, because even the pack is always encased
> >      in pktlines for smart-http.
> 
> So something like this. It turned out to be a lot uglier than I had
> hoped because we get fed the data from curl in odd-sized chunks, so we
> need a state machine.
> 
> But it does seem to work. At least it doesn't seem to break anything in
> the test suite, and it fixes the new tests you added. I'd worry that
> there's some obscure case where the response isn't packetized in the
> same way.

Actually, I take it back. I think it works for a single round of ref negotiation, but not for multiple. Enabling GIT_TEST_LONG=1 causes it to fail t5551.

I think I've probably made a mis-assumption on exactly when in the HTTP protocol we will see a flush packet (and perhaps that is a sign that this protocol-snooping approach is not a good one).

I don't have time to dig more on this tonight, and I'll be traveling for the rest of the week. So if anybody is interested, please feel free to dig into it.

-Peff