Describes the state of a pipeline.

PIPELINE_STATE_UNSPECIFIED The pipeline state is unspecified.
PIPELINE_STATE_QUEUED The pipeline has been created or resumed, and processing has not yet begun.
PIPELINE_STATE_PENDING The service is preparing to run the pipeline.
PIPELINE_STATE_RUNNING The pipeline is in progress.
PIPELINE_STATE_SUCCEEDED The pipeline completed successfully.
PIPELINE_STATE_FAILED The pipeline failed.
PIPELINE_STATE_CANCELLING The pipeline is being cancelled. From this state, the pipeline may only go to either PIPELINE_STATE_SUCCEEDED, PIPELINE_STATE_FAILED or PIPELINE_STATE_CANCELLED.
PIPELINE_STATE_CANCELLED The pipeline has been cancelled.
PIPELINE_STATE_PAUSED The pipeline has been stopped, and can be resumed.