FireX Kit provides:

  • A FireXTask class derived from Celery’s base Task class that facilitates passing of arguments and return values from one task to another, which is particularly useful when using Chains.

  • A mechanism to elegantly and dynamically convert task arguments.

  • Helper functions that faciliate checking for readiness of AsyncResult objects.

Argument Passing made easy

FireX Kit uses a simple concept we refer to as the Bag Of Goodies (BOG), which can be visualized as a dictionary of argument/value pairs from which a task can pick the subset of arguments it requires, and might choose to update the BOG with returned key/value pairs. This dynamic dictionary then moves to the next task in the chain, which will in turn can consume some of the arguments it requires, as well as optionally add or update the BOG with its returns.

Consider a chain comprised of Task A, Task B, and Task C. If these tasks derives from FireXTask class, the arguments and return values will flow as depicted in the following diagram:


In the above example:

  • The user invokes a chain Task A | Task B | Task C, providing arguments k1, k2 and k3, with values v1, v2, and v3 respectively (i.e., the initial BOG).

  • Task A will only consume k1: v1 from the Initial BOG. It will then add to the BOG its own returns, i.e., k4: v4.

  • Task B will consume k1: v1 provided initially by the user, as well as k4: v4 which was returned by the preceeding Task A.

  • Task C consumes k3: v3, but also adds its returns k5: v7 to the BOG.

Few things are noteworthy:

  • A FireXTask like Task A, Task B, and Task C does not need to consume **kwargs in order to enable it to consume extra arguments that it doesn’t need. For example, Task A’s signature contains only k1. The other arguments will not provided to TaskA.

  • There is only one BOG in a given chain, so, if a task in the chain returns the same key as an element that already exists in the BOG, the original value of that key will be replaced, as was the case with k4 update by Task B in the example above.

Below is another simple example of two FireXTask tasks: