Cron expressions should follow the machine local time, not UTC [closes #173]

.gitignore

@@ -18,5 +18,4 @@ platypush/notebooks
 platypush/requests
 /http-client.env.json
 /platypush/backend/http/static/css/dist
-/tests/etc/scripts
 /tests/etc/dashboards

CHANGELOG.md

@@ -3,6 +3,13 @@
 All notable changes to this project will be documented in this file.
 Given the high speed of development in the first phase, changes are being reported only starting from v0.20.2.
 
+## [unreleased]
+
+### Fixed
+
+- Cron expressions should adhere to the UNIX cronjob standard and use the machine local time,
+  not UTC, as a reference (closes [#173](https://git.platypush.tech/platypush/platypush/-/issues/173)).
+
 ## [0.20.4] - 2021-03-08
 
 ### Added

platypush/cron/scheduler.py

@@ -1,9 +1,10 @@
+import datetime
 import enum
 import logging
 import threading
-import time
 
 import croniter
+from dateutil.tz import gettz
 
 from platypush.procedure import Procedure
 from platypush.utils import is_functional_cron
@@ -56,16 +57,10 @@ class Cronjob(threading.Thread):
             self.state = CronjobState.ERROR
 
     def wait(self):
-        now = int(time.time())
+        now = datetime.datetime.now().replace(tzinfo=gettz())
         cron = croniter.croniter(self.cron_expression, now)
-        next_run = int(cron.get_next())
+        next_run = cron.get_next()
-        self._should_stop.wait(next_run - now)
+        self._should_stop.wait(next_run - now.timestamp())
-
-    def should_run(self):
-        now = int(time.time())
-        cron = croniter.croniter(self.cron_expression, now)
-        next_run = int(cron.get_next())
-        return now == next_run
 
     def stop(self):
         self._should_stop.set()
@@ -117,7 +112,7 @@ class CronScheduler(threading.Thread):
                 if job.state == CronjobState.IDLE:
                     job.start()
 
-            time.sleep(0.5)
+            self._should_stop.wait(timeout=0.5)
 
         logger.info('Terminating cron scheduler')
 

tests/etc/scripts/__init__.py

@@ -0,0 +1 @@
+# Auto-generated __init__.py - do not remove

tests/etc/scripts/test_cron.py

@@ -0,0 +1,26 @@
+import datetime
+
+from platypush.cron import cron
+
+from tests.test_cron import tmp_files, tmp_files_ready, \
+    test_timeout, expected_cron_file_content
+
+# 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(cron_expr)
+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)
+
+    with open(tmp_files[0], 'w') as f:
+        f.write(expected_cron_file_content)

tests/test_cron.py

@@ -0,0 +1,46 @@
+import os
+import pytest
+import tempfile
+import threading
+import time
+
+tmp_files = []
+tmp_files_ready = threading.Event()
+test_timeout = 10
+expected_cron_file_content = 'The cronjob ran successfully!'
+
+
+@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
+
+    if os.path.isfile(tmp_files[0]):
+        os.unlink(tmp_files[0])
+
+
+def test_cron_execution(tmp_file):
+    """
+    Test that the cronjob in ``../etc/scripts/test_cron.py`` runs successfully.
+    """
+    actual_cron_file_content = None
+    test_start = time.time()
+
+    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)
+
+
+if __name__ == '__main__':
+    pytest.main()
+
+
+# vim:sw=4:ts=4:et: