Tasks occasionally fail with Duplicate entry

[operinko]

Heya,

Any idea what could be causing this?

[2013-04-21 23:56:41,435: ERROR/MainProcess] Task thing.history_updater[3bc080ed-1029-4f23-9da1-2981b52c7b79] raised exception: IntegrityError(1062, "Duplicate entry '10000002-16274-2013-04-20' for key 'thing_pricehistory_region_id_35fc85aebfeaf766_uniq'")
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/celery/task/trace.py", line 228, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/celery/task/trace.py", line 415, in __protected_call__
    return self.run(*args, **kwargs)
  File "/var/www/evething/evething/thing/tasks/historyupdater.py", line 65, in run
    PriceHistory.objects.bulk_create(new)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 140, in bulk_create
    return self.get_query_set().bulk_create(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 419, in bulk_create
    self._batched_insert(objs_without_pk, fields, batch_size)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 868, in _batched_insert
    using=self.db)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 203, in _insert
    return insert_query(self.model, objs, fields, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 1593, in insert_query
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py", line 912, in execute_sql
    cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/base.py", line 114, in execute
    return self.cursor.execute(query, args)
  File "/usr/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 174, in execute
    self.errorhandler(self, exc, value)
  File "/usr/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue

[madcowfred]

That shouldn't be possible at all unless you have two history_updater tasks running at the same time.. which also shouldn't ever happen. How often does this occur?

[operinko]

Judging by my logs, it happens a few times / day, so it's not too big of a deal.
I've my site set up with rabbitmq-server running 3 queues (high, med, low, although I've changed some of the designations of the queued items).

I haven't noticed duplicate jobs in the db, and that's just about as much as I know how to check.