定时任务调度-Celery
Posted liujiliang
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确保任务不重叠解决方法:
from celery import task from celery.five import monotonic from celery.utils.log import get_task_logger from contextlib import contextmanager from django.core.cache import cache from hashlib import md5 from djangofeeds.models import Feed logger = get_task_logger(__name__) LOCK_EXPIRE = 60 * 10 # Lock expires in 10 minutes @contextmanager def memcache_lock(lock_id, oid): timeout_at = monotonic() + LOCK_EXPIRE - 3 # cache.add fails if the key already exists status = cache.add(lock_id, oid, LOCK_EXPIRE) try: yield status finally: # memcache delete is very slow, but we have to use it to take # advantage of using add() for atomic locking if monotonic() < timeout_at and status: # don‘t release the lock if we exceeded the timeout # to lessen the chance of releasing an expired lock # owned by someone else # also don‘t release the lock if we didn‘t acquire it cache.delete(lock_id) @task(bind=True) def import_feed(self, feed_url): # The cache key consists of the task name and the MD5 digest # of the feed URL. feed_url_hexdigest = md5(feed_url).hexdigest() lock_id = ‘{0}-lock-{1}‘.format(self.name, feed_url_hexdigest) logger.debug(‘Importing feed: %s‘, feed_url) with memcache_lock(lock_id, self.app.oid) as acquired: if acquired: return Feed.objects.import_feed(feed_url).url logger.debug( ‘Feed %s is already being imported by another worker‘, feed_url)
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