Class _chord

celery/canvas.py:1950–2365

r"""Barrier synchronization primitive. A chord consists of a header and a body. The header is a group of tasks that must complete before the callback is called. A chord is essentially a callback for a group of tasks. The body is applied with the return values of all the header

@Signature.register_type(name=class="st">"chord")
class _chord(Signature):
    rclass="st">"""Barrier synchronization primitive.

    A chord consists of a header and a body.

    The header is a group of tasks that must complete before the callback is
    called.  A chord is essentially a callback for a group of tasks.

    The body is applied with the return values of all the header
    tasks as a list.

    Example:

        The chord:

        .. code-block:: pycon

            >>> res = chord([add.s(2, 2), add.s(4, 4)])(sum_task.s())

        is effectively :math:`\Sigma ((2 + 2) + (4 + 4))`:

        .. code-block:: pycon

            >>> res.get()
            12
    class="st">"""

    @classmethod
    def from_dict(cls, d, app=None):
        class="st">"""Create a chord signature from a dictionary that represents a chord.

        Example:
            >>> chord_dict = {
                class="st">"task": class="st">"celery.chord",
                class="st">"args": [],
                class="st">"kwargs": {
                    class="st">"kwargs": {},
                    class="st">"header": [
                        {
                            class="st">"task": class="st">"add",
                            class="st">"args": [
                                1,
                                2
                            ],
                            class="st">"kwargs": {},
                            class="st">"options": {},
                            class="st">"subtask_type": None,
                            class="st">"immutable": False
                        },
                        {
                            class="st">"task": class="st">"add",
                            class="st">"args": [
                                3,
                                4
                            ],
                            class="st">"kwargs": {},
                            class="st">"options": {},
                            class="st">"subtask_type": None,