GCSBackend

Google Cloud Storage task result backend.

Uses Firestore for chord ref count.

Attributes

Attribute	Type	Description
implements_incr	boolean = True	Boolean flag indicating that this backend supports atomic increment operations used for chord synchronization.
supports_native_join	boolean = True	Boolean flag indicating that this backend can perform native join operations for task groups.

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Constructor

Signature

def GCSBackend(
    **kwargs: dict
) - > null

Parameters

Name	Type	Description
**kwargs	dict	Arbitrary keyword arguments passed to the base class constructor.

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Methods

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firestore_client()

@classmethod
def firestore_client() - > google.cloud.firestore.Client

Returns a firestore client.

Returns

Type	Description
google.cloud.firestore.Client	A thread-safe Firestore client instance associated with the configured project.

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incr()

@classmethod
def incr(
    key: bytes
) - > int

Increments the chord counter for a specific key in Firestore using an atomic operation with built-in retry logic for conflicts.

Parameters

Name	Type	Description
key	bytes	The unique identifier for the chord tracking document in Firestore.

Returns

Type	Description
int	The new integer value of the chord counter after the increment.

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on_chord_part_return()

@classmethod
def on_chord_part_return(
    request: object,
    state: string,
    result: any
) - > null

Chord part return callback. Called for each task in the chord. Increments the counter stored in Firestore. If the counter reaches the number of tasks in the chord, the callback is called. If the callback raises an exception, the chord is marked as errored. If the callback returns a value, the chord is marked as successful.

Parameters

Name	Type	Description
request	object	The request object for the individual task part, containing group and chord metadata.
state	string	The current execution state of the task part.
result	any	The return value of the individual task part.

Returns

Type	Description
null	null

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