Sebastiaan van Stijn b39739123b cli: perform feature detection lazily ... - Perform feature detection when actually needed, instead of during initializing - Version negotiation is performed either when making an API request, or when (e.g.) running `docker help` (to hide unsupported features) - Use a 2 second timeout when 'pinging' the daemon; this should be sufficient for most cases, and when feature detection failed, the daemon will still perform validation (and produce an error if needed) - context.WithTimeout doesn't currently work with ssh connections (connhelper), so we're only applying this timeout for tcp:// connections, otherwise keep the old behavior. Before this change: time sh -c 'DOCKER_HOST=tcp://42.42.42.41:4242 docker help &> /dev/null' real 0m32.919s user 0m0.370s sys 0m0.227s time sh -c 'DOCKER_HOST=tcp://42.42.42.41:4242 docker context ls &> /dev/null' real 0m32.072s user 0m0.029s sys 0m0.023s After this change: time sh -c 'DOCKER_HOST=tcp://42.42.42.41:4242 docker help &> /dev/null' real 0m 2.28s user 0m 0.03s sys 0m 0.03s time sh -c 'DOCKER_HOST=tcp://42.42.42.41:4242 docker context ls &> /dev/null' real 0m 0.13s user 0m 0.02s sys 0m 0.02s Signed-off-by: Sebastiaan van Stijn <github@gone.nl>		2020-04-10 16:33:21 +02:00
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docker	cli: perform feature detection lazily	2020-04-10 16:33:21 +02:00