forked from platypush/platypush
Fix for #217
The cron scheduler has been made more robust against changes in the system clock (caused by e.g. DST changes, NTP syncs or manual setting). A more granular management for cronjob events has been introduced, now supporting a `TIME_SYNC` event besides the usual `STOP`. When the cron scheduler detects a system clock drift (i.e. the timestamp offset before and after a blocking wait is >1 sec) then all the cronjobs are notified and forced to refresh their state.
This commit is contained in:
parent
820a1c8184
commit
41d0725ebf
3 changed files with 148 additions and 63 deletions
|
@ -7,11 +7,20 @@ import croniter
|
|||
from dateutil.tz import gettz
|
||||
|
||||
from platypush.procedure import Procedure
|
||||
from platypush.utils import is_functional_cron
|
||||
from platypush.utils import is_functional_cron, set_thread_name
|
||||
|
||||
logger = logging.getLogger('platypush:cron')
|
||||
|
||||
|
||||
def get_now() -> datetime.datetime:
|
||||
"""
|
||||
:return: A timezone-aware representation of `now`
|
||||
"""
|
||||
return datetime.datetime.now().replace(
|
||||
tzinfo=gettz()
|
||||
) # lgtm [py/call-to-non-callable]
|
||||
|
||||
|
||||
class CronjobState(enum.IntEnum):
|
||||
IDLE = 0
|
||||
WAIT = 1
|
||||
|
@ -20,21 +29,36 @@ class CronjobState(enum.IntEnum):
|
|||
ERROR = 4
|
||||
|
||||
|
||||
class CronjobEvent(enum.IntEnum):
|
||||
NONE = 0
|
||||
STOP = 1
|
||||
TIME_SYNC = 2
|
||||
|
||||
|
||||
class Cronjob(threading.Thread):
|
||||
def __init__(self, name, cron_expression, actions):
|
||||
super().__init__()
|
||||
self.cron_expression = cron_expression
|
||||
self.name = name
|
||||
self.state = CronjobState.IDLE
|
||||
self._should_stop = threading.Event()
|
||||
self._event = threading.Event()
|
||||
self._event_type = CronjobEvent.NONE
|
||||
self._event_lock = threading.RLock()
|
||||
|
||||
if isinstance(actions, dict) or isinstance(actions, list):
|
||||
self.actions = Procedure.build(name=name + '__Cron', _async=False, requests=actions)
|
||||
if isinstance(actions, (list, dict)):
|
||||
self.actions = Procedure.build(
|
||||
name=name + '__Cron', _async=False, requests=actions
|
||||
)
|
||||
else:
|
||||
self.actions = actions
|
||||
|
||||
def notify(self, event: CronjobEvent):
|
||||
with self._event_lock:
|
||||
self._event_type = event
|
||||
self._event.set()
|
||||
|
||||
def run(self):
|
||||
self.state = CronjobState.WAIT
|
||||
set_thread_name(f'cron:{self.name}')
|
||||
self.wait()
|
||||
if self.should_stop():
|
||||
return
|
||||
|
@ -57,26 +81,38 @@ class Cronjob(threading.Thread):
|
|||
self.state = CronjobState.ERROR
|
||||
|
||||
def wait(self):
|
||||
now = datetime.datetime.now().replace(tzinfo=gettz()) # lgtm [py/call-to-non-callable]
|
||||
cron = croniter.croniter(self.cron_expression, now)
|
||||
next_run = cron.get_next()
|
||||
self._should_stop.wait(next_run - now.timestamp())
|
||||
with self._event_lock:
|
||||
self.state = CronjobState.WAIT
|
||||
self._event.clear()
|
||||
self._event_type = CronjobEvent.TIME_SYNC
|
||||
|
||||
while self._event_type == CronjobEvent.TIME_SYNC:
|
||||
now = get_now()
|
||||
self._event_type = CronjobEvent.NONE
|
||||
cron = croniter.croniter(self.cron_expression, now)
|
||||
next_run = cron.get_next()
|
||||
self._event.wait(max(0, next_run - now.timestamp()))
|
||||
|
||||
def stop(self):
|
||||
self._should_stop.set()
|
||||
self._event_type = CronjobEvent.STOP
|
||||
self._event.set()
|
||||
|
||||
def should_stop(self):
|
||||
return self._should_stop.is_set()
|
||||
return self._event_type == CronjobEvent.STOP
|
||||
|
||||
|
||||
class CronScheduler(threading.Thread):
|
||||
def __init__(self, jobs):
|
||||
def __init__(self, jobs, poll_seconds: float = 0.5):
|
||||
super().__init__()
|
||||
self.jobs_config = jobs
|
||||
self._jobs = {}
|
||||
self._poll_seconds = max(1e-3, poll_seconds)
|
||||
self._should_stop = threading.Event()
|
||||
logger.info('Cron scheduler initialized with {} jobs'.
|
||||
format(len(self.jobs_config.keys())))
|
||||
logger.info(
|
||||
'Cron scheduler initialized with {} jobs'.format(
|
||||
len(self.jobs_config.keys())
|
||||
)
|
||||
)
|
||||
|
||||
def _get_job(self, name, config):
|
||||
job = self._jobs.get(name)
|
||||
|
@ -84,14 +120,21 @@ class CronScheduler(threading.Thread):
|
|||
return job
|
||||
|
||||
if isinstance(config, dict):
|
||||
self._jobs[name] = Cronjob(name=name, cron_expression=config['cron_expression'],
|
||||
actions=config['actions'])
|
||||
self._jobs[name] = Cronjob(
|
||||
name=name,
|
||||
cron_expression=config['cron_expression'],
|
||||
actions=config['actions'],
|
||||
)
|
||||
elif is_functional_cron(config):
|
||||
self._jobs[name] = Cronjob(name=name, cron_expression=config.cron_expression,
|
||||
actions=config)
|
||||
self._jobs[name] = Cronjob(
|
||||
name=name, cron_expression=config.cron_expression, actions=config
|
||||
)
|
||||
else:
|
||||
raise AssertionError('Expected type dict or function for cron {}, got {}'.format(
|
||||
name, type(config)))
|
||||
raise AssertionError(
|
||||
'Expected type dict or function for cron {}, got {}'.format(
|
||||
name, type(config)
|
||||
)
|
||||
)
|
||||
|
||||
return self._jobs[name]
|
||||
|
||||
|
@ -112,7 +155,22 @@ class CronScheduler(threading.Thread):
|
|||
if job.state == CronjobState.IDLE:
|
||||
job.start()
|
||||
|
||||
self._should_stop.wait(timeout=0.5)
|
||||
t_before_wait = get_now().timestamp()
|
||||
self._should_stop.wait(timeout=self._poll_seconds)
|
||||
t_after_wait = get_now().timestamp()
|
||||
time_drift = abs(t_after_wait - t_before_wait) - self._poll_seconds
|
||||
|
||||
if not self.should_stop() and time_drift > 1:
|
||||
# If the system clock has been adjusted by more than one second
|
||||
# (e.g. because of DST change or NTP sync) then ensure that the
|
||||
# registered cronjobs are synchronized with the new datetime
|
||||
logger.info(
|
||||
'System clock drift detected: %f secs. Synchronizing the cronjobs',
|
||||
time_drift,
|
||||
)
|
||||
|
||||
for job in self._jobs.values():
|
||||
job.notify(CronjobEvent.TIME_SYNC)
|
||||
|
||||
logger.info('Terminating cron scheduler')
|
||||
|
||||
|
|
|
@ -2,25 +2,34 @@ import datetime
|
|||
|
||||
from platypush.cron import cron
|
||||
|
||||
from tests.test_cron import tmp_files, tmp_files_ready, \
|
||||
test_timeout, expected_cron_file_content
|
||||
from tests.test_cron import test_timeout, cron_queue
|
||||
|
||||
|
||||
def make_cron_expr(cron_time: datetime.datetime):
|
||||
return '{min} {hour} {day} {month} * {sec}'.format(
|
||||
min=cron_time.minute,
|
||||
hour=cron_time.hour,
|
||||
day=cron_time.day,
|
||||
month=cron_time.month,
|
||||
sec=cron_time.second,
|
||||
)
|
||||
|
||||
|
||||
# Prepare a cronjob that should start test_timeout/2 seconds from the application start
|
||||
cron_time = datetime.datetime.now() + datetime.timedelta(seconds=test_timeout/2)
|
||||
cron_expr = '{min} {hour} {day} {month} * {sec}'.format(
|
||||
min=cron_time.minute, hour=cron_time.hour, day=cron_time.day,
|
||||
month=cron_time.month, sec=cron_time.second)
|
||||
cron_time = datetime.datetime.now() + datetime.timedelta(seconds=test_timeout / 2)
|
||||
|
||||
|
||||
@cron(cron_expr)
|
||||
@cron(make_cron_expr(cron_time))
|
||||
def cron_test(**_):
|
||||
"""
|
||||
Simple cronjob that awaits for ``../test_cron.py`` to be ready and writes the expected
|
||||
content to the monitored temporary file.
|
||||
"""
|
||||
files_ready = tmp_files_ready.wait(timeout=test_timeout)
|
||||
assert files_ready, \
|
||||
'The test did not prepare the temporary files within {} seconds'.format(test_timeout)
|
||||
cron_queue.put('cron_test')
|
||||
|
||||
with open(tmp_files[0], 'w') as f:
|
||||
f.write(expected_cron_file_content)
|
||||
|
||||
# Prepare another cronjob that should start 1hr + test_timeout/2 seconds from the application start
|
||||
cron_time = datetime.datetime.now() + datetime.timedelta(
|
||||
hours=1, seconds=test_timeout / 2
|
||||
)
|
||||
|
||||
|
||||
@cron(make_cron_expr(cron_time))
|
||||
def cron_1hr_test(**_):
|
||||
cron_queue.put('cron_1hr_test')
|
||||
|
|
|
@ -1,43 +1,61 @@
|
|||
import os
|
||||
import datetime
|
||||
import queue
|
||||
import pytest
|
||||
import tempfile
|
||||
import threading
|
||||
import time
|
||||
|
||||
tmp_files = []
|
||||
tmp_files_ready = threading.Event()
|
||||
from dateutil.tz import gettz
|
||||
from mock import patch
|
||||
|
||||
test_timeout = 10
|
||||
expected_cron_file_content = 'The cronjob ran successfully!'
|
||||
cron_queue = queue.Queue()
|
||||
|
||||
|
||||
@pytest.fixture(scope='module', autouse=True)
|
||||
def tmp_file(*_):
|
||||
tmp_file = tempfile.NamedTemporaryFile(prefix='platypush-test-cron-',
|
||||
suffix='.txt', delete=False)
|
||||
tmp_files.append(tmp_file.name)
|
||||
tmp_files_ready.set()
|
||||
yield tmp_file.name
|
||||
class MockDatetime(datetime.datetime):
|
||||
timedelta = datetime.timedelta()
|
||||
|
||||
for f in tmp_files:
|
||||
if os.path.isfile(f):
|
||||
os.unlink(f)
|
||||
@classmethod
|
||||
def now(cls):
|
||||
return super().now(tz=gettz()) + cls.timedelta
|
||||
|
||||
|
||||
def test_cron_execution(tmp_file):
|
||||
def _test_cron_queue(expected_msg: str):
|
||||
msg = None
|
||||
test_start = time.time()
|
||||
while time.time() - test_start <= test_timeout and msg != expected_msg:
|
||||
try:
|
||||
msg = cron_queue.get(block=True, timeout=test_timeout)
|
||||
except queue.Empty:
|
||||
break
|
||||
|
||||
assert msg == expected_msg, 'The expected cronjob has not been executed'
|
||||
|
||||
|
||||
def test_cron_execution():
|
||||
"""
|
||||
Test that the cronjob in ``../etc/scripts/test_cron.py`` runs successfully.
|
||||
"""
|
||||
actual_cron_file_content = None
|
||||
test_start = time.time()
|
||||
_test_cron_queue('cron_test')
|
||||
|
||||
while actual_cron_file_content != expected_cron_file_content and \
|
||||
time.time() - test_start < test_timeout:
|
||||
with open(tmp_file, 'r') as f:
|
||||
actual_cron_file_content = f.read()
|
||||
time.sleep(0.5)
|
||||
|
||||
assert actual_cron_file_content == expected_cron_file_content, \
|
||||
'cron_test failed to run within {} seconds'.format(test_timeout)
|
||||
def test_cron_execution_upon_system_clock_change():
|
||||
"""
|
||||
Test that the cronjob runs at the right time even upon DST or other
|
||||
system clock changes.
|
||||
"""
|
||||
# Mock datetime.datetime with a class that has overridable timedelta
|
||||
patcher = patch('datetime.datetime', MockDatetime)
|
||||
|
||||
try:
|
||||
patcher.start()
|
||||
time.sleep(1)
|
||||
# Simulate a +1hr shift on the system clock
|
||||
MockDatetime.timedelta = datetime.timedelta(hours=1)
|
||||
time.sleep(1)
|
||||
finally:
|
||||
patcher.stop()
|
||||
|
||||
# Ensure that the cronjob that was supposed to run in an hour is now running
|
||||
_test_cron_queue('cron_1hr_test')
|
||||
|
||||
|
||||
if __name__ == '__main__':
|
||||
|
|
Loading…
Reference in a new issue