id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	launchpad_bug
1338	reduce CLI startup overhead by importing less	davidsarah	daira	"{{{bin/tahoe}}} takes about 3.5 seconds to perform a trivial command (e.g. {{{bin/tahoe --help}}}) on my machine. Most of this overhead is due to importing dependencies: [source:src/allmydata/__init__.py] imports ''all'' of Tahoe's dependencies, in order to check their versions.

Just removing the calls to {{{get_package_versions_and_locations()}}} and {{{check_all_requirements()}}} does not work; we end up importing most of these libraries anyway. However, most of the CLI commands that do not start a node, ''should not'' need to import anything except {{{twisted.python.usage}}}.

By copying just the files that are needed for the CLI to work at all, and removing imports that are not really necessary, I was able to get the time to run {{{bin/tahoe --help}}} on my machine to 1.1 seconds, i.e. a factor-of-3 improvement. This is just a proof of concept at the moment, but I think this improvement could also be obtained for the real CLI. Note that just running a script that prints out the help text takes 0.8 seconds, due to the startup overhead of the Python interpreter.

Another major advantage of doing this is that the resulting CLI could be embedded as a library, without pulling in any of Tahoe's dependencies and their associated packaging woes."	defect	assigned	major	soon	code-frontend-cli	1.8.1		performance extensibility packaging	tahoe-lafs.org@…