Launching steps

The workflow engine launches Steps (Jobs/Instances) in response to either a WorkflowMessage (START) message or a PodMessage (for a successful step completion).

Starting a workflow

A new workflow starts when the engine receives a WorkflowMessage where action="START".

For the simple linear engine implementation the engine can assume that the first step declared in the workflow is the first step to execute.

As well as identifying the first step, one of the most important parts of the engine's responsibilities is the formation of a dictionary of variables that it needs to pass to the InstanceLauncher in order to actually start the step. The engine must provide names and values for all the variables the first step declares as inputs, options, and outputs.

Continuing a workflow

Stopping a workflow