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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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| Makefile | ||
| README | ||
| client.go | ||
| main.go | ||
| proxy.go | ||
| socket.go | ||
git-remote-persistent-https The git-remote-persistent-https binary speeds up SSL operations by running a daemon job (git-remote-persistent-https--proxy) that keeps a connection open to a server. PRE-BUILT BINARIES Darwin amd64: https://commondatastorage.googleapis.com/git-remote-persistent-https/darwin_amd64.tar.gz Linux amd64: https://commondatastorage.googleapis.com/git-remote-persistent-https/linux_amd64.tar.gz INSTALLING Move all of the git-remote-persistent-http* binaries to a directory in PATH. USAGE HTTPS requests can be delegated to the proxy by using the "persistent-https" scheme, e.g. git clone persistent-https://kernel.googlesource.com/pub/scm/git/git Likewise, .gitconfig can be updated as follows to rewrite https urls to use persistent-https: [url "persistent-https"] insteadof = https [url "persistent-http"] insteadof = http ##################################################################### # BUILDING FROM SOURCE ##################################################################### LOCATION The source is available in the contrib/persistent-https directory of the Git source repository. The Git source repository is available at git://git.kernel.org/pub/scm/git/git.git/ https://kernel.googlesource.com/pub/scm/git/git PREREQUISITES The code is written in Go (http://golang.org/) and the Go compiler is required. Currently, the compiler must be built and installed from tip of source, in order to include a fix in the reverse http proxy: http://code.google.com/p/go/source/detail?r=a615b796570a2cd8591884767a7d67ede74f6648 BUILDING Run "make" to build the binaries. See the section on INSTALLING above.