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Author	SHA1	Message	Date
Colby Ranger	fe0435011c	Add persistent-https to contrib 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>	13 years ago

Author

SHA1

Message

Date

Colby Ranger

fe0435011c

Add persistent-https to contrib

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>

13 years ago

1 Commits (fcf2cfb54b6be34749feb6ffb50fe2bdd7bac8bc)