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.

stateDiagram-v2
    [*] --> Begin
    Begin --> DoneWithoutRunning: RunNever
    Begin --> WaitingDependencySteps: RunConditional
    WaitingDependencySteps --> WaitingDependencySteps: DependencyStepsRunning
    WaitingDependencySteps --> CheckingMissingDependencies: DependencyStepsFinishedSuccessfully
    WaitingDependencySteps --> Broken: DependencyStepsFinishedBroken
    WaitingDependencySteps --> CheckingMissingDependencies: DependencyStepsFinishedBrokenIgnored
    CheckingMissingDependencies --> CheckingMissingDependencies: MissingDependenciesIgnored
    CheckingMissingDependencies --> Broken: HasMissingDependencies
    CheckingMissingDependencies --> CheckingMissingOutputs: NoMissingDependencies
    CheckingMissingOutputs --> CheckingMissingOutputs: MissingOutputsIgnored
    CheckingMissingOutputs --> CheckingTimestamps: NoMissingOutputs
    CheckingMissingOutputs --> WaitingToRun: HasMissingOutputs
    CheckingTimestamps --> CheckingTimestamps: TimestampsIgnored
    CheckingTimestamps --> CheckingDependencyContentDigest: HasNoNewerDependencies
    CheckingTimestamps --> WaitingToRun: HasNewerDependencies
    CheckingDependencyContentDigest --> WaitingToRun: ContentDigestIgnored
    CheckingDependencyContentDigest --> DoneWithoutRunning: ContentDigestNotChanged
    CheckingDependencyContentDigest --> WaitingToRun: ContentDigestChanged
    DoneWithoutRunning --> Done: CompletedWithoutRunningStep
    WaitingToRun --> WaitingToRun: ProcessPoolFull
    WaitingToRun --> Running: StartProcess
    WaitingToRun --> Broken: CannotStartProcess
    Running --> Running: WaitProcess
    Running --> Broken: ProcessTimeout
    Running --> Done: ProcessCompletedSuccessfully
    Running --> Broken: ProcessReturnedNonZero
    Broken --> Broken: HasBroken
    Done --> Done: HasDone
    Done --> [*]
    Broken --> [*]

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.