The point of t5559 is run the regular t5551 tests with HTTP/2. But it
does so with the "h2c" protocol, which uses cleartext upgrades from
HTTP/1.1 to HTTP/2 (rather than learning about HTTP/2 support during the
TLS negotiation).
This has a few problems:
- it's not very indicative of the real world. In practice, most servers
that support HTTP/2 will also support TLS.
- support for upgrading does not seem as robust. In particular, we've
run into bugs in some versions of Apache's mod_http2 that trigger
only with the upgrade mode. See:
https://lore.kernel.org/git/Y8ztIqYgVCPILJlO@coredump.intra.peff.net/
So the upside is that this change makes our HTTP/2 tests more robust and
more realistic. The downside is that if we can't set up SSL for any
reason, we'll skip the tests (even though you _might_ have been able to
run the HTTP/2 tests the old way). We could probably have a conditional
fallback, but it would be complicated for little gain, and it's not even
clear it would help (i.e., would any test environment even have HTTP/2
but not SSL support?).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We have occasionally seen bugs that affect Git running only against an
HTTP/2 web server, not an HTTP one. For instance, b66c77a64e (http:
match headers case-insensitively when redacting, 2021-09-22). But since
we have no test coverage using HTTP/2, we only uncover these bugs in the
wild.
That commit gives a recipe for converting our Apache setup to support
HTTP/2, but:
- it's not necessarily portable
- we don't want to just test HTTP/2; we really want to do a variety of
basic tests for _both_ protocols
This patch handles both problems by running a duplicate of t5551
(labeled as t5559 here) with an alternate-universe setup that enables
HTTP/2. So we'll continue to run t5551 as before, but run the same
battery of tests again with HTTP/2. If HTTP/2 isn't supported on a given
platform, then t5559 should bail during the webserver setup, and
gracefully skip all tests (unless GIT_TEST_HTTPD has been changed from
"auto" to "yes", where the point is to complain when webserver setup
fails).
In theory other http-related test scripts could benefit from the same
duplication, but doing t5551 should give us a reasonable check of basic
functionality, and would have caught both bugs we've seen in the wild
with HTTP/2.
A few notes on the implementation:
- a script enables the server side config by calling enable_http2
before starting the webserver. This avoids even trying to load any
HTTP/2 config for t5551 (which is what lets it keep working with
regular HTTP even on systems that don't support it). This also sets
a prereq which can be used by individual tests.
- As discussed in b66c77a64e, the http2 module isn't compatible with
the "prefork" mpm, so we need to pick something else. I chose
"event" here, which works on my Debian system, but it's possible
there are platforms which would prefer something else. We can adjust
that later if somebody finds such a platform.
- The test "large fetch-pack requests can be sent using chunked
encoding" makes sure we use a chunked transfer-encoding by looking
for that header in the trace. But since HTTP/2 has its own streaming
mechanisms, we won't find such a header. We could skip the test
entirely by marking it with !HTTP2. But there's some value in making
sure that the fetch itself succeeded. So instead, we'll confirm that
either we're using HTTP2 _or_ we saw the expected chunked header.
- the redaction tests fail under HTTP/2 with recent versions of curl.
This is a bug! I've marked them with !HTTP2 here to skip them under
t5559 for the moment. Using test_expect_failure would be more
appropriate, but would require a bunch of boilerplate. Since we'll
be fixing them momentarily, let's just skip them for now to keep the
test suite bisectable, and we can re-enable them in the commit that
fixes the bug.
- one alternative layout would be to push most of t5551 into a
lib-t5551.sh script, then source it from both t5551 and t5559.
Keeping t5551 intact seemed a little simpler, as its one less level
of indirection for people fixing bugs/regressions in the non-HTTP/2
tests.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
