ui: add an uninterruptable context manager that can block SIGINT
The blocking of SIGINT is not done by default, but my hope is that we
will one day. This was inspired by Facebook's "nointerrupt" extension,
which is a bit more heavy-handed than this (whole commands are treated
as unsafe to interrupt). A future patch will enable this for varying
bits of Mercurial that are performing unsafe operations.
It's intentional that the KeyboardInterrupt is raised as the context
manager exits: during the span of the context manager interrupting
Mercurial could lead to data loss, but typically those spans are
fairly narrow, so we can let the unsafe block complete and then
terminate hg (which will leave the repo in a consistent state, even if
it's not the user's desired state).
.. api::
New context manager ``ui.uninterruptable()`` to mark portions of a command
as potentially unsafe places to interrupt Mercurial with Control-C or
similar.
Differential Revision: https://phab.mercurial-scm.org/D3716
Dummy extension simulating unsafe long running command
$ cat > sleepext.py <<EOF
> import time
> import itertools
>
> from mercurial import registrar
> from mercurial.i18n import _
>
> cmdtable = {}
> command = registrar.command(cmdtable)
>
> @command(b'sleep', [], _(b'TIME'), norepo=True)
> def sleep(ui, sleeptime=b"1", **opts):
> with ui.uninterruptable():
> for _i in itertools.repeat(None, int(sleeptime)):
> time.sleep(1)
> ui.warn(b"end of unsafe operation\n")
> ui.warn(b"%s second(s) passed\n" % sleeptime)
> EOF
Kludge to emulate timeout(1) which is not generally available.
$ cat > timeout.py <<EOF
> from __future__ import print_function
> import argparse
> import signal
> import subprocess
> import sys
> import time
>
> ap = argparse.ArgumentParser()
> ap.add_argument('-s', nargs=1, default='SIGTERM')
> ap.add_argument('duration', nargs=1, type=int)
> ap.add_argument('argv', nargs='*')
> opts = ap.parse_args()
> try:
> sig = int(opts.s[0])
> except ValueError:
> sname = opts.s[0]
> if not sname.startswith('SIG'):
> sname = 'SIG' + sname
> sig = getattr(signal, sname)
> proc = subprocess.Popen(opts.argv)
> time.sleep(opts.duration[0])
> proc.poll()
> if proc.returncode is None:
> proc.send_signal(sig)
> proc.wait()
> sys.exit(124)
> EOF
Set up repository
$ hg init repo
$ cd repo
$ cat >> $HGRCPATH << EOF
> [extensions]
> sleepext = ../sleepext.py
> EOF
Test ctrl-c
$ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
interrupted!
[124]
$ cat >> $HGRCPATH << EOF
> [experimental]
> nointerrupt = yes
> EOF
$ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
interrupted!
[124]
$ cat >> $HGRCPATH << EOF
> [experimental]
> nointerrupt-interactiveonly = False
> EOF
$ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
shutting down cleanly
press ^C again to terminate immediately (dangerous)
end of unsafe operation
interrupted!
[124]