upload-pack: send keepalive while feeding pack-objects#2160
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When upload-pack feeds revision OIDs to pack-objects via pipe, there is a gap where no data is sent to the HTTP client. With many wants (e.g. 50k+ refs), this pipe feeding can take seconds as write() blocks on the pipe when the kernel buffer fills up. Meanwhile, an HTTP server sitting in front of git (e.g. Apache) may time out waiting for CGI output and kill the process. The existing keepalive mechanism in create_pack_file's poll loop handles keepalive after pack-objects starts producing output, but does not cover the earlier pipe feeding phase. Extend keepalive coverage by sending empty sideband packets during the pipe feeding loops, using the same "0005\1" format that the poll loop already uses. This reuses the existing uploadpack.keepalive config with no new options required. Signed-off-by: Kristofer Karlsson <krka@spotify.com>
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When upload-pack feeds revision OIDs to pack-objects via pipe, there is a gap where no data is sent to the HTTP client. With many wants (e.g. 50k+ refs), this pipe feeding can take seconds as write() blocks on the pipe when the kernel buffer fills up. Meanwhile, an HTTP server sitting in front of git (e.g. Apache) may time out waiting for CGI output and kill the process.
The existing keepalive mechanism in create_pack_file's poll loop handles keepalive after pack-objects starts producing output, but does not cover the earlier pipe feeding phase.
This extends keepalive coverage by sending empty sideband packets during the pipe feeding loops, using the same
0005\1format that the poll loop already uses. This reuses the existinguploadpack.keepaliveconfig with no new options required.cc: Jeff King peff@peff.net
cc: Patrick Steinhardt ps@pks.im