What is a task

In a lesson in the previous module, you defined a pipeline and modified its input datastream in a live solution. Each time you changed the input datastream, the pipeline executed its defined operations and populated the resulting value in the pipeline's output datastream. These executions were able to occur because of tasks.

When you define a pipeline, you also define a pipeline task. In a live solution, an instance of the pipeline task is executed each time the input datastream(s) for the pipeline are updated. The completion of a task instance also triggers the execution of tasks for downstream components that depend on the output datastreams.

Pipeline tasks are not the only type of task on the Elara platform. In later modules, you will learn about other Components of a solution that also have Tasks, such as Datasources and Datasinks.

A task instance has a state, which updates as the instance executes. The possible states of a task instance are described in the table below:

State	Description
enqueued	The task is queued and waiting to be executed (since execution is yet to occur, output datastream values are unchanged).
running	The task instance is executing currently.
success	The task instance has executed successfully, and all output datastream values have been updated.
warn	The task has finished executing and updated output datastream values. However, possible issues have been flagged and warning messages have been logged.
error	The task has not executed successfully and output datastream values have not been updated. Error messages describing the nature of the failure(s) have been logged.
cancelled	The task execution was terminated before completion and output datastream values have not been updated.

Data about task instances (such as their state, execution start time, completion time, etc) are captured together with task logs in Elara platform, which you can access via the Elara platform API, the EDK CLI, and/or the User Interface. Task status and logs are the primary way that you validate the status of your solution without resorting to reading datastreams to validate outputs.

Next steps

In the next tutorial you will learn how to use the EDK CLI to access Elara platform logging and monitor the execution of Tasks.