Groups

You can group together results by passing async_task() the optional group keyword:

# result group example
from django_q.tasks import async_task, result_group

for i in range(4):
    async_task('math.modf', i, group='modf')

# wait until the group has 4 results
result = result_group('modf', count=4)
print(result)

[(0.0, 0.0), (0.0, 1.0), (0.0, 2.0), (0.0, 3.0)]

Note that this particular example can be achieved much faster with Iterable

Take care to not limit your results database too much and call delete_group() before each run, unless you want your results to keep adding up. Instead of result_group() you can also use fetch_group() to return a queryset of Task objects.:

# fetch group example
from django_q.tasks import fetch_group, count_group, result_group

# count the number of failures
failure_count = count_group('modf', failures=True)

# only use the successes
results = fetch_group('modf')
if failure_count:
    results = results.exclude(success=False)
results =  [task.result for task in successes]

# this is the same as
results = fetch_group('modf', failures=False)
results =  [task.result for task in successes]

# and the same as
results = result_group('modf') # filters failures by default

Getting results by using result_group() is of course much faster than using fetch_group(), but it doesn’t offer the benefits of Django’s queryset functions.

Note

Calling Queryset.values for the result on Django 1.7 or lower will return a list of encoded results. If you can’t upgrade to Django 1.8, use list comprehension or an iterator to return decoded results.

You can also access group functions from a task result instance:

from django_q.tasks import fetch

task = fetch('winter-speaker-alpha-ceiling')
if  task.group_count() > 100:
    print(task.group_result())
    task.group_delete()
    print('Deleted group {}'.format(task.group))

or call them directly on AsyncTask object:

from django_q.tasks import AsyncTask

# add a task to the math group and run it cached
a = AsyncTask('math.floor', 2.5, group='math', cached=True)

# wait until this tasks group has 10 results
result = a.result_group(count=10)

Reference

result_group(group_id, failures=False, wait=0, count=None, cached=False)

Returns the results of a task group

Parameters:
  • group_id (str) – the group identifier
  • failures (bool) – set this to True to include failed results
  • wait (int) – optional milliseconds to wait for a result or count. -1 for indefinite
  • count (int) – block until there are this many results in the group
  • cached (bool) – run this against the cache backend
Returns:

a list of results
Return type:

list
fetch_group(group_id, failures=True, wait=0, count=None, cached=False)

Returns a list of tasks in a group

Parameters:
  • group_id (str) – the group identifier
  • failures (bool) – set this to False to exclude failed tasks
  • wait (int) – optional milliseconds to wait for a task or count. -1 for indefinite
  • count (int) – block until there are this many tasks in the group
  • cached (bool) – run this against the cache backend.
Returns:

a list of Task
Return type:

list
count_group(group_id, failures=False, cached=False)

Counts the number of task results in a group.

Parameters:
  • group_id (str) – the group identifier
  • failures (bool) – counts the number of failures if True
  • cached (bool) – run this against the cache backend.
Returns:

the number of tasks or failures in a group
Return type:

int
delete_group(group_id, tasks=False, cached=False)

Deletes a group label from the database.

Parameters:
  • group_id (str) – the group identifier
  • tasks (bool) – also deletes the associated tasks if True
  • cached (bool) – run this against the cache backend.
Returns:

the numbers of tasks affected
Return type:

int