From faa55daccf2a3d33a6a9e3c901c703d5ee81c52d Mon Sep 17 00:00:00 2001
From: Fabio Manganiello <blacklight86@gmail.com>
Date: Sat, 28 Sep 2019 01:34:27 +0200
Subject: [PATCH] Smarter cron management with croniter

---
 docs/source/conf.py         |  1 +
 platypush/cron/scheduler.py | 96 +++++++++++++++++++------------------
 requirements.txt            |  3 ++
 setup.py                    |  1 +
 4 files changed, 55 insertions(+), 46 deletions(-)

diff --git a/docs/source/conf.py b/docs/source/conf.py
index 016f9a5fc..18126f981 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -225,6 +225,7 @@ autodoc_mock_imports = ['googlesamples.assistant.grpc.audio_helpers',
                         'picamera',
                         'pwm3901',
                         'PIL',
+                        'croniter',
                         ]
 
 sys.path.insert(0, os.path.abspath('../..'))
diff --git a/platypush/cron/scheduler.py b/platypush/cron/scheduler.py
index 5b67b7da7..121aec5f3 100644
--- a/platypush/cron/scheduler.py
+++ b/platypush/cron/scheduler.py
@@ -1,8 +1,9 @@
-import datetime
+import enum
 import logging
-import re
 import time
 
+import croniter
+
 from threading import Thread
 
 from platypush.procedure import Procedure
@@ -10,76 +11,79 @@ from platypush.procedure import Procedure
 logger = logging.getLogger(__name__)
 
 
+class CronjobState(enum.IntEnum):
+    IDLE = 0
+    WAIT = 1
+    RUNNING = 2
+    DONE = 3
+    ERROR = 4
+
+
 class Cronjob(Thread):
-    def __init__(self, name, cron_expression, actions, *args, **kwargs):
+    def __init__(self, name, cron_expression, actions):
         super().__init__()
         self.cron_expression = cron_expression
         self.name = name
-        self.actions = Procedure.build(name=name+'__Cron', _async=False,
+        self.state = CronjobState.IDLE
+        self.actions = Procedure.build(name=name + '__Cron', _async=False,
                                        requests=actions)
 
-
     def run(self):
-        logger.info('Running cronjob {}'.format(self.name))
-        response = None
-        context = {}
-        response = self.actions.execute(_async=False, **context)
-        logger.info('Response from cronjob {}: {}'.format(self.name, response))
+        self.state = CronjobState.WAIT
+        self.wait()
+        self.state = CronjobState.RUNNING
 
+        try:
+            logger.info('Running cronjob {}'.format(self.name))
+            context = {}
+            response = self.actions.execute(_async=False, **context)
+            logger.info('Response from cronjob {}: {}'.format(self.name, response))
+            self.state = CronjobState.DONE
+        except Exception as e:
+            logger.exception(e)
+            self.state = CronjobState.ERROR
+
+    def wait(self):
+        now = int(time.time())
+        cron = croniter.croniter(self.cron_expression, now)
+        next_run = int(cron.get_next())
+        time.sleep(next_run - now)
 
     def should_run(self):
-        units = ('minute', 'hour', 'day', 'month', 'year')
-        now = datetime.datetime.fromtimestamp(time.time())
-        cron_units = re.split('\s+', self.cron_expression)
-
-        for i in range(0, len(units)):
-            unit = units[i]
-            now_unit = getattr(now, unit)
-            cron_unit = cron_units[i].replace('*', str(now_unit))
-            m = re.match('(\d+)(/(\d+))?', cron_unit)
-
-            if m.group(3):
-                if int(m.group(1)) % int(m.group(3)):
-                    return False
-            elif m:
-                if int(m.group(1)) != now_unit:
-                    return False
-            else:
-                raise RuntimeError('Invalid cron expression for job {}: {}'.
-                                   format(self.name, self.cron_expression))
-
-        return True
+        now = int(time.time())
+        cron = croniter.croniter(self.cron_expression, now)
+        next_run = int(cron.get_next())
+        return now == next_run
 
 
 class CronScheduler(Thread):
-    def __init__(self, jobs, *args, **kwargs):
+    def __init__(self, jobs):
         super().__init__()
         self.jobs_config = jobs
-        logger.info('Cron scheduler initialized with {} jobs'
-                     .format(len(self.jobs_config.keys())))
+        self._jobs = {}
+        logger.info('Cron scheduler initialized with {} jobs'.
+                    format(len(self.jobs_config.keys())))
 
+    def _get_job(self, name, config):
+        job = self._jobs.get(name)
+        if job and job.state not in [CronjobState.DONE, CronjobState.ERROR]:
+            return job
 
-    @classmethod
-    def _build_job(cls, name, config):
-        if isinstance(config, dict):
-            job = Cronjob(name=name, cron_expression=config['cron_expression'],
-                          actions=config['actions'])
-
-        assert isinstance(job, Cronjob)
-        return job
+        self._jobs[name] = Cronjob(name=name, cron_expression=config['cron_expression'],
+                                   actions=config['actions'])
 
+        return self._jobs[name]
 
     def run(self):
         logger.info('Running cron scheduler')
 
         while True:
             for (job_name, job_config) in self.jobs_config.items():
-                job = self._build_job(name=job_name, config=job_config)
-                if job.should_run():
+                job = self._get_job(name=job_name, config=job_config)
+                if job.state == CronjobState.IDLE:
                     job.start()
 
-            time.sleep(60)
+            time.sleep(0.5)
 
 
 # vim:sw=4:ts=4:et:
-
diff --git a/requirements.txt b/requirements.txt
index 8c9539807..cd3e35bfe 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -172,3 +172,6 @@ pyScss
 # Support for machine learning CV plugin
 # cv2
 # numpy
+
+# Support for cronjobs
+croniter
diff --git a/setup.py b/setup.py
index e956e8c67..ffe714b3c 100755
--- a/setup.py
+++ b/setup.py
@@ -133,6 +133,7 @@ setup(
         'pyyaml',
         'redis',
         'requests',
+        'croniter',
     ],
     extras_require = {
         'Support for custom thread and process names': ['python-prctl'],