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Task is a fundamental building block and an extension point of Flyte, which encapsulates the users’ code. They possess the following properties:
Versioned (usually tied to the
Strong interfaces (specified inputs and outputs)
A task in Flytekit can be of two types:
A task that has a Python function associated with it. The execution of the task is equivalent to the execution of this function.
A task that doesn’t have a Python function, e.g., an SQL query or any portable task like Sagemaker prebuilt algorithms, or a service that invokes an API.
Flyte provides multiple plugins for tasks, which can be a backend plugin as well (Athena).
In this example, you will learn how to write and execute a
Python function task. Other types of tasks will be covered in the later sections.
For any task in Flyte, there is one necessary import, which is:
from flytekit import task
PythonFunctionTask must always be decorated with the
The task in itself is a regular Python function, although with one exception: it needs all the inputs and outputs to be clearly
annotated with the types. The types are regular Python types; we’ll go over more on this in the type-system section.
@task def square(n: int) -> int: """ Parameters: n (int): name of the parameter for the task will be derived from the name of the input variable the type will be automatically deduced to be Types.Integer Return: int: The label for the output will be automatically assigned and type will be deduced from the annotation """ return n * n
In this task, one input is
n which has type
square takes the number
n and returns a new integer (squared value).
Flytekit will assign a default name to the output variable like
In case of multiple outputs, each output will be numbered in the order
starting with 0, e.g., ->
out0, out1, out2, ....
You can execute a Flyte task as any normal function.
if __name__ == "__main__": print(square(n=10))
Invoke a Task within a Workflow#
The primary way to use Flyte tasks is to invoke them in the context of a workflow.
from flytekit import workflow @workflow def wf(n: int) -> int: return square(n=square(n=n))
In this toy example, we’re calling the
square task twice and returning the result.
Execute a Single Task without a Workflow
Although workflows are traditionally composed of multiple tasks with dependencies defined by shared inputs and outputs, it can be helpful to execute a single task during the process of iterating on its definition. It can be tedious to write a new workflow definition every time you want to execute a single task under development but “single task executions” can be used to iterate on task logic easily.
You can launch a task on Flyte console by providing a Kubernetes service account.
Alternatively, you can use
flytectl to launch the task. Run the following commands in the
This example is building a Docker image and pushing it only for the demo sandbox
environment. For a production cluster, you will have to push the image to a Docker registry.
For the next command to work make sure that you start the sandbox from
flytesnacks/cookbook directory with
flytectl demo start --source .
Build a Docker image to package the task.
flytectl demo exec -- docker build . --tag "flytebasics:v1" -f core/Dockerfile
Package the task.
pyflyte --pkgs core.flyte_basics package --image flytebasics:v1
Register the task.
flytectl register files --project flytesnacks --domain development --archive flyte-package.tgz --version v1
Generate an execution spec file.
flytectl get task --domain development --project flytesnacks core.flyte_basics.task.square --version v1 --execFile exec_spec.yaml
Create an execution using the exec spec file.
flytectl create execution --project flytesnacks --domain development --execFile exec_spec.yaml
For subsequent executions, you can simply run
flytectl create execution ... and skip the previous commands.
Alternatively, you can launch the task from the Flyte console.
Monitor the execution by providing the execution name from the create execution command.
flytectl get execution --project flytesnacks --domain development <execname>
Total running time of the script: ( 0 minutes 0.000 seconds)