--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wiki/tasks.py	Mon Nov 12 15:10:52 2012 -0600
@@ -0,0 +1,48 @@
+"""
+Celery tasks for the wiki app.
+
+"""
+import datetime
+import logging
+import time
+
+from celery.task import task
+from django.conf import settings
+import redis
+
+from core.services import get_redis_connection
+
+
+logger = logging.getLogger(__name__)
+
+
+@task
+def expire_cookies():
+    """
+    Periodically run this task to remove expired cookies from the Redis set
+    that is shared between this Django application & the MoinMoin wiki for
+    authentication.
+
+    """
+    now = datetime.datetime.utcnow()
+    cutoff = now - datetime.timedelta(seconds=settings.WIKI_COOKIE_AGE)
+    min_score = time.mktime(cutoff.utctimetuple())
+
+    conn = get_redis_connection()
+
+    set_name = settings.WIKI_REDIS_SET
+    try:
+        count = conn.zcard(set_name)
+    except redis.RedisError:
+        logger.error("Error getting zcard")
+        return
+
+    try:
+        removed = conn.zremrangebyscore(set_name, 0.0, min_score)
+    except redis.RedisError:
+        logger.error("Error removing by score")
+        return
+
+    total = count - removed
+    logger.info("Expire wiki cookies: removed %d, total is now %d",
+            removed, total)