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The "persistent-https" remote helper supposedly speeds up SSL operations
by running a daemon that keeps a connection open to a remote server. It
is effectively unmaintained nowadays: the last time it received an
update was in accb613afd2 (contrib/persistent-https: use Git version for
build label, 2016-07-20) and its parent commits to make it compile with
Go 1.7+.
This Go toolchain is somewhat dated by now though and unsupported. The
oldest still-supported toolchain is Go 1.23, which was released in
August 2024. It is not possible to compile the remote helper with that
Go version anymore:
$ go version
go version go1.23.8 linux/amd64
$ make
case $(go version) in \
"go version go"1.[0-5].*) EQ=" " ;; *) EQ="=" ;; esac && \
go build -o git-remote-persistent-https \
-ldflags "-X main._BUILD_EMBED_LABEL${EQ}GIT_VERSION=2.49.0.943.g965a70ebf62"
go: cannot find main module, but found .git/config in /home/pks/Development/git
to create a module there, run:
cd ../.. && go mod init
make: *** [Makefile:31: git-remote-persistent-https] Error 1
The problem is that modern Go toolchains require a "go.mod" file, but we
don't have any such files. This requirement exists since quite a while
already, so it's clear that nobody has tried to use this remote helper
anytime recent.
Remove the remote helper.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Git over HTTPS has a high request startup latency, since the SSL
negotiation can take up to a second. In order to reduce this latency,
connections should be left open to the Git server across requests
(or invocations of the git commandline).
Reduce SSL startup latency by running a daemon job that keeps
connections open to a Git server. The daemon job
(git-remote-persistent-https--proxy) is started on the first request
through the client binary (git-remote-persistent-https) and remains
running for 24 hours after the last request, or until a new daemon
binary is placed in the PATH. The client determines the daemon's
HTTP address by communicating over a UNIX socket with the daemon.
From there, the rest of the Git protocol work is delegated to the
"git-remote-http" binary, with the environment's http_proxy set to
the daemon.
Accessing /pub/scm/linux/kernel/git/torvalds/linux repository hosted
at kernel.googlesource.com with "git ls-remote" over https:// and
persistent-https:// 5 times shows that the first request takes about
the same time (0.193s vs 0.208s---there is a slight set-up cost for
the local proxy); as expected, the other four requests are much
faster (~0.18s vs ~0.08s).
Incidentally, this also has the benefit of HTTP keep-alive working
across Git command invocations. Its common for servers to use a 5
minute keep-alive on an HTTP 1.1 connection. Git-over-HTTP commonly
uses Transfer-Encoding: chunked on replies, so keep-alive will
generally just work, even though a pack stream's length isn't known
in advance. Because the helper is an external process holding that
connection open, we also benefit from being able to reuse an
existing TCP connection to the server. The same "git ls-remote"
test against http:// vs persistent-https:// URL shows that the
former takes ~0.09s while the first request for the latter is about
0.134s with set-up cost, and subsequent requests are ~0.065s,
shaving around one RTT to the server.
Signed-off-by: Colby Ranger <cranger@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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