from hashlib import sha224 from logging import getLogger from time import time from django.contrib.auth.models import User from django.core.cache import cache from django.db.models import (CharField, DateTimeField, ForeignKey, NullBooleanField, TextField) from django.utils import timezone from django.utils.translation import ugettext_lazy as _ from model_utils.models import TimeStampedModel logger = getLogger(__name__) class WorkerNotFound(Exception): pass def activitycontextimpl(act, on_abort=None, on_commit=None): try: yield act except BaseException as e: # BaseException is the common parent of Exception and # system-exiting exceptions, e.g. KeyboardInterrupt handler = None if on_abort is None else lambda a: on_abort(a, e) act.finish(succeeded=False, result=str(e), event_handler=handler) raise e else: act.finish(succeeded=True, event_handler=on_commit) class ActivityModel(TimeStampedModel): activity_code = CharField(max_length=100, verbose_name=_('activity code')) parent = ForeignKey('self', blank=True, null=True, related_name='children') task_uuid = CharField(blank=True, max_length=50, null=True, unique=True, help_text=_('Celery task unique identifier.'), verbose_name=_('task_uuid')) user = ForeignKey(User, blank=True, null=True, verbose_name=_('user'), help_text=_('The person who started this activity.')) started = DateTimeField(verbose_name=_('started at'), blank=True, null=True, help_text=_('Time of activity initiation.')) finished = DateTimeField(verbose_name=_('finished at'), blank=True, null=True, help_text=_('Time of activity finalization.')) succeeded = NullBooleanField(blank=True, null=True, help_text=_('True, if the activity has ' 'finished successfully.')) result = TextField(verbose_name=_('result'), blank=True, null=True, help_text=_('Human readable result of activity.')) def __unicode__(self): if self.parent: return self.parent.activity_code + "->" + self.activity_code else: return self.activity_code class Meta: abstract = True def finish(self, succeeded, result=None, event_handler=None): if not self.finished: self.finished = timezone.now() self.succeeded = succeeded if result is not None: self.result = result if event_handler is not None: event_handler(self) self.save() @property def has_succeeded(self): return self.finished and self.succeeded @property def has_failed(self): return self.finished and not self.succeeded def method_cache(memcached_seconds=60, instance_seconds=5): # noqa """Cache return value of decorated method to memcached and memory. :param memcached_seconds: Invalidate memcached results after this time. :param instance_seconds: Invalidate results cached to static memory after this time. If a result is cached on instance, return that first. If that fails, check memcached. If all else fails, run the method and cache on instance and in memcached. Do not use for methods with side effects. Instances are hashed by their id attribute, args by their unicode representation. ** NOTE: Methods that return None are always "recached". Based on https://djangosnippets.org/snippets/2477/ """ def inner_cache(method): def get_key(instance, *args, **kwargs): return sha224(unicode(method.__module__) + unicode(method.__name__) + unicode(instance.id) + unicode(args) + unicode(kwargs)).hexdigest() def x(instance, *args, **kwargs): invalidate = kwargs.pop('invalidate_cache', False) now = time() key = get_key(instance, *args, **kwargs) result = None try: vals = getattr(instance, key) except AttributeError: pass else: if vals['time'] + instance_seconds > now: # has valid on class cache, return that result = vals['value'] if result is None: result = cache.get(key) if invalidate or (result is None): # all caches failed, call the actual method result = method(instance, *args, **kwargs) # save to memcache and class attr cache.set(key, result, memcached_seconds) setattr(instance, key, {'time': now, 'value': result}) logger.debug('Value of <%s>.%s(%s)=<%s> saved to cache.', unicode(instance), method.__name__, unicode(args), unicode(result)) return result return x return inner_cache