Re: [PATCH v7 2/2] http-backend: respect CONTENT_LENGTH for receive-pack

From: Jeff King <peff@peff.net>
Date: Jun 11, 2018, 09:18 UTC
Message-ID: <20180611091813.GB16414@sigill.intra.peff.net>
In-Reply-To: <20180604221807.GC27650@jessie.local>

On Tue, Jun 05, 2018 at 01:18:08AM +0300, Max Kirillov wrote:

Show 9 quoted lines

> > On Sun, Jun 03, 2018 at 12:27:49AM +0300, Max Kirillov wrote:
> > Since this is slightly less efficient, and because it only matters if
> > the web server does not already close the pipe, should this have a
> > run-time configuration knob, even if it defaults to
> > safe-but-slightly-slower?
> 
> Personally, I of course don't want this. Also, I don't think
> the difference is much noticeable. But you can never be sure
> without trying. I'll try to measure some numbers.

I don't know if it will matter or not. I just wonder if we want to leave an escape hatch for people who might. I could take or leave it.

> Actually, it is already 3rd same error in this file. Maybe
> deserve some refactoring. I will change the message also.

Thanks, that kind of related cleanup is very welcome.

Show 5 quoted lines

> > We generally prefer to have all commands, even ones we don't expect to
> > fail, inside test_expect blocks (e.g., with a "setup" description).
> 
> Will the defined variables get to the next test? I'll try to
> do as you describe.

Yes, the tests are all run as evals. So as long as you don't open a subshell yourself, any changes you make to process state will persist.

Show 14 quoted lines

> >> +test_expect_success 'fetch plain truncated' '
> >> +	test_http_env upload \
> >> +		"$TEST_DIRECTORY"/t5562/invoke-with-content-length.pl fetch_body.trunc git http-backend >act.out 2>act.err &&
> >> +	test_must_fail verify_http_result "200 OK"
> >> +'
> > 
> > Usually test_must_fail on a checking function like this is a sign that
> > the check is not as robust as we'd like. If the function checks two
> > things "A && B", then checking test_must_fail will only let us know
> > "!A || !B", but you probably want to check both.
> 
> Well here I just want to know that the request has failed,
> and we already know that it can fail in different ways,
> but the test is not going to differentiate those ways.

OK, looking over your verify_http_result function, I _think_ we are OK here, because the only && is against a printf, which we wouldn't really expect to fail.

Show 12 quoted lines

> >> +sleep 1; # is interrupted by SIGCHLD
> >> +if (!$exited) {
> >> +        close($out);
> >> +        die "Command did not exit after reading whole body";
> >> +}
> 
> > Also, do we need to protect ourselves against other signals being
> > delivered? E.g., if I resize my xterm and this process gets SIGWINCH, is
> > it going to erroneously end the sleep and say "nope, no exited signal"?
> 
> I'll check, but what could I do? Should I add blocking other
> signals there?

I think a more robust check may be to waitpid() on the child for up to N seconds. Something like this:

  $SIG{ALRM} = sub {
	  kill(9, $pid);
	  die "command did not exit after reading whole body"
  };
  alarm(60);
  waitpid($pid, 0);
  alarm(0);

That should exit immediately if $pid does, and otherwise die after exactly 60 seconds. Perl's waitpid implementation will restart automatically if it gets another signal.

-Peff