subiquity/subiquity/journald.py

50 lines
1.5 KiB
Python

# Copyright 2020 Canonical, Ltd.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import contextlib
from systemd import journal
def journald_listen(loop, identifiers, callback, seek=False):
reader = journal.Reader()
args = []
for identifier in identifiers:
args.append("SYSLOG_IDENTIFIER={}".format(identifier))
reader.add_match(*args)
if seek:
reader.seek_tail()
def watch():
if reader.process() != journal.APPEND:
return
for event in reader:
callback(event)
loop.add_reader(reader.fileno(), watch)
return reader.fileno()
@contextlib.contextmanager
def journald_subscriptions(loop, ids_callbacks, seek=False):
fds = set()
for id, callback in ids_callbacks:
fds.add(journald_listen(loop, [id], callback, seek=seek))
try:
yield
finally:
for fd in fds:
loop.remove_reader(fd)