testing interleaved long-running requests in django

Question

I am trying to write tests for django requests which might take a long time to process, and thus might interleave with other requests. My plan was to issue a long-running request, and inject assertions into places where it might suspend.

But trying to use threading in my unit test doesn't seem to work well:

class ThreadTest(test.TestCase):
    def thread_test(self):
        def printer():
            print models.Daemon.objects.count()

        d = models.Daemon(url='http://lockss.notadomain:8088')
        d.save()
        printer()
        t = threading.Thread(target=printer)
        t.start()
        t.join()

The printer() call works as I'd expect the first time, but then when called from a Thread is unable to find the table:

1
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.6/threading.py", line 484, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/home/bhayes/lockss-code/hare/lockss-django/autest/tests.py", line 247, in printer
    print models.Daemon.objects.count()
  File "/usr/lib/pymodules/python2.6/django/db/models/manager.py", line 120, in count
    return self.get_query_set().count()
  File "/usr/lib/pymodules/python2.6/django/db/models/query.py", line 326, in count
    return self.query.get_count(using=self.db)
  File "/usr/lib/pymodules/python2.6/django/db/models/sql/query.py", line 394, in get_count
    number = obj.get_aggregation(using=using)[None]
  File "/usr/lib/pymodules/python2.6/django/db/models/sql/query.py", line 366, in get_aggregation
    result = query.get_compiler(using).execute_sql(SINGLE)
  File "/usr/lib/pymodules/python2.6/django/db/models/sql/compiler.py", line 727, in execute_sql
    cursor.execute(sql, params)
  File "/usr/lib/pymodules/python2.6/django/db/backends/sqlite3/base.py", line 200, in execute
    return Database.Cursor.execute(self, query, params)
DatabaseError: no such table: autest_daemon

I'd like to understand what's going on. Also, I'd like to know if there is a better strategy for testing parallel requests.

Answer 1

You can not use threading with in memory databases (sqlite3 in this case) in Django see this bug. Your test would probably work with PostgreSQL or MySQL.