Merge pull request Tivix#102 from HousekeepLtd/dry-run

Add cron feedback and dry-run functionality

Author: dgominik

django_cron/__init__.py

@@ -2,6 +2,7 @@
 from datetime import timedelta
 import traceback
 import time
+import sys
 
 from django.conf import settings
 from django.utils.timezone import now as utc_now, localtime, is_naive
@@ -12,13 +13,21 @@
 logger = logging.getLogger('django_cron')
 
 
+class BadCronJobError(AssertionError):
+    pass
+
+
 def get_class(kls):
     """
     TODO: move to django-common app.
     Converts a string to a class.
     Courtesy: http://stackoverflow.com/questions/452969/does-python-have-an-equivalent-to-java-class-forname/452981#452981
     """
     parts = kls.split('.')
+
+    if len(parts) == 1:
+        raise ImportError("'{0}'' is not a valid import path".format(kls))
+
     module = ".".join(parts[:-1])
     m = __import__(module)
     for comp in parts[1:]:
@@ -77,12 +86,11 @@ class CronJobManager(object):
     Used as a context manager via 'with' statement to ensure
     proper logger in cases of job failure.
     """
-
-    def __init__(self, cron_job_class, silent=False, *args, **kwargs):
-        super(CronJobManager, self).__init__(*args, **kwargs)
-
+    def __init__(self, cron_job_class, silent=False, dry_run=False, stdout=None):
         self.cron_job_class = cron_job_class
         self.silent = silent
+        self.dry_run = dry_run
+        self.stdout = stdout or sys.stdout
         self.lock_class = self.get_lock_class()
         self.previously_ran_successful_cron = None
 
@@ -92,7 +100,6 @@ def should_run_now(self, force=False):
         """
         Returns a boolean determining whether this cron should run now or not!
         """
-
         self.user_time = None
         self.previously_ran_successful_cron = None
 
@@ -170,11 +177,20 @@ def __enter__(self):
         return self
 
     def __exit__(self, ex_type, ex_value, ex_traceback):
-        if ex_type == self.lock_class.LockFailedException:
+        if ex_type is None:
+            return True
+
+        non_logging_exceptions = [
+            BadCronJobError, self.lock_class.LockFailedException
+        ]
+
+        if ex_type in non_logging_exceptions:
             if not self.silent:
+                self.stdout.write("{0}\n".format(ex_value))
                 logger.info(ex_value)
-
-        elif ex_type is not None:
+        else:
+            if not self.silent:
+                self.stdout.write(u"[\N{HEAVY BALLOT X}] {0}\n".format(self.cron_job_class.code))
             try:
                 trace = "".join(traceback.format_exception(ex_type, ex_value, ex_traceback))
                 self.make_log(self.msg, trace, success=False)
@@ -189,17 +205,29 @@ def run(self, force=False):
         apply the logic of the schedule and call do() on the CronJobBase class
         """
         cron_job_class = self.cron_job_class
+
         if not issubclass(cron_job_class, CronJobBase):
-            raise Exception('The cron_job to be run must be a subclass of %s' % CronJobBase.__name__)
+            raise BadCronJobError('The cron_job to be run must be a subclass of %s' % CronJobBase.__name__)
+
+        if not hasattr(cron_job_class, 'code'):
+            raise BadCronJobError(
+                "Cron class '{0}' does not have a code attribute"
+                .format(cron_job_class.__name__)
+            )
 
         with self.lock_class(cron_job_class, self.silent):
             self.cron_job = cron_job_class()
 
             if self.should_run_now(force):
-                logger.debug("Running cron: %s code %s", cron_job_class.__name__, self.cron_job.code)
-                self.msg = self.cron_job.do()
-                self.make_log(self.msg, success=True)
-                self.cron_job.set_prev_success_cron(self.previously_ran_successful_cron)
+                if not self.dry_run:
+                    logger.debug("Running cron: %s code %s", cron_job_class.__name__, self.cron_job.code)
+                    self.msg = self.cron_job.do()
+                    self.make_log(self.msg, success=True)
+                    self.cron_job.set_prev_success_cron(self.previously_ran_successful_cron)
+                if not self.silent:
+                    self.stdout.write(u"[\N{HEAVY CHECK MARK}] {0}\n".format(self.cron_job.code))
+            elif not self.silent:
+                self.stdout.write(u"[ ] {0}\n".format(self.cron_job.code))
 
     def get_lock_class(self):
         name = getattr(settings, 'DJANGO_CRON_LOCK_BACKEND', DEFAULT_LOCK_BACKEND)

django_cron/management/commands/runcrons.py

@@ -1,3 +1,4 @@
+from __future__ import print_function
 import traceback
 from datetime import timedelta
 
@@ -28,41 +29,60 @@ def add_arguments(self, parser):
             action='store_true',
             help='Do not push any message on console'
         )
+        parser.add_argument(
+            '--dry-run',
+            action='store_true',
+            help="Just show what crons would be run; don't actually run them"
+        )
 
     def handle(self, *args, **options):
         """
         Iterates over all the CRON_CLASSES (or if passed in as a commandline argument)
         and runs them.
         """
+        if not options['silent']:
+            self.stdout.write("Running Crons\n")
+            self.stdout.write("{0}\n".format("=" * 40))
+
         cron_classes = options['cron_classes']
         if cron_classes:
             cron_class_names = cron_classes
         else:
             cron_class_names = getattr(settings, 'CRON_CLASSES', [])
 
-        crons_to_run = [get_class(x) for x in cron_class_names]
+        try:
+            crons_to_run = [get_class(x) for x in cron_class_names]
+        except ImportError:
+            error = traceback.format_exc()
+            self.stdout.write('ERROR: Make sure these are valid cron class names: %s\n\n%s' % (cron_class_names, error))
+            return
 
         for cron_class in crons_to_run:
             run_cron_with_cache_check(
                 cron_class,
                 force=options['force'],
-                silent=options['silent']
+                silent=options['silent'],
+                dry_run=options['dry_run'],
+                stdout=self.stdout
             )
 
         clear_old_log_entries()
         close_old_connections()
 
 
-def run_cron_with_cache_check(cron_class, force=False, silent=False):
+def run_cron_with_cache_check(
+    cron_class, force=False, silent=False, dry_run=False, stdout=None
+):
     """
     Checks the cache and runs the cron or not.
 
     @cron_class - cron class to run.
     @force      - run job even if not scheduled
     @silent     - suppress notifications
+    @dryrun     - don't actually perform the cron job
+    @stdout     - where to write feedback to
     """
-
-    with CronJobManager(cron_class, silent) as manager:
+    with CronJobManager(cron_class, silent=silent, dry_run=dry_run, stdout=stdout) as manager:
         manager.run(force)