Xvc Pipelines State Machine

Xvc pipelines use a state machine to track the progress of each step. Each step has a state that is updated as the pipeline is executed.

A step starts in the Begin state. It must wait for all its dependency steps if --when is set to by_dependencies (the default) in xvc pipeline step new or xvc pipeline step update. If this option is set to never, the step will never run and will move to the DoneWithoutRunning state just after begin. If this option is set to always, the step will run regardless of the changes in the dependencies and will move to the WaitingDependencySteps even if dependencies are missing, broken, or have not changed.

If --when option is set to by_dependencies, the steps check the following conditions before running:

• All dependency steps must be in the Done state.
• There should be no missing dependency files.
• There should be no broken dependency processes.
• Dependency files should be newer, or the content digest should be different from the step outputs.

If any of these conditions are met, the step will move to the WaitingDependencySteps state.