We were checking for whether an item in the deployments directory
represents a directory but were using its relative path which was
causing a false value to be returned for all items irrespective of
their being a directory or not if the script was invoked from some
where other than the deployments directory.
This commit re-arranges the arguments of `purge_unused_caches()`
function in order to remain consistent with other similar functions
in the library like `may_be_perform_caching()`.
This function will replace the repetitive definition of `parse_args()`
in various cache cleaning scripts. Also adds a `--verbose` argument
to the parser.
Based on the `dry_run` flag, this function either purges the list
of directories passed to them or prints a listing of the directories
it would have purged/kept_back, had the `dry_run` flag been false.
Given the path of directory containing all the caches, a list of
caches in use and threshold days, this function returns a list
of caches which can be removed safely.
This function returns a list of all the deployments directories
which are newer than some threshold number of days including the
`/root/zulip` directory if it exists.
This saves us from spending 200-250ms of CPU time importing Django
again just to log that we're running a management command. On
`scripts/restart-server`, this saves us from one thundering herd of
Django startups when all the queue workers are restarted; but there's
still the Django startup for the `manage.py` process itself for each
worker, so on a machine with e.g. 2 (virtual) cores the restart is
still painful.
This causes `upgrade-zulip-from-git`, as well as a no-option run of
`tools/build-release-tarball`, to produce a Zulip install running
Python 3, rather than Python 2. In particular this means that the
virtualenv we create, in which all application code runs, is Python 3.
One shebang line, on `zulip-ec2-configure-interfaces`, explicitly
keeps Python 2, and at least one external ops script, `wal-e`, also
still runs on Python 2. See discussion on the respective previous
commits that made those explicit. There may also be some other
third-party scripts we use, outside of this source tree and running
outside our virtualenv, that still run on Python 2.
For performance reasons, we spawn each linter in a separate OS thread.
The downside of this is that all lints would end up in stdout without
much visual separation, resulting in confusing error log. This commit
introduce the `print_err` function, which shows which linter each line
of lint is from.
