Pipeline execution

Wraps any failure that occurred while running a pipeline, reported as its root fault.

The runner raises it around every failure that happens once a run has started, so a host catches one class whatever went wrong. You will rarely see PipelineExecutionError as the error_type of a report, though: the report names what actually went wrong.

What the report says

The report of a PipelineExecutionError is the report of its root fault, the innermost Pipelex error on its cause chain, located at the pipe that failed:

• error_type, title and type_uri are the root fault's. A run whose model was not found reports ModelNotFoundError, and a run whose parallel branch could not be combined reports StuffFactoryError.
• message is the root fault's own message, prefixed with the failing pipe and its path from the entry pipe: Pipe 'summarize' failed (two_steps → summarize): Model handle 'x' was not found in the model deck. When the entry pipe itself failed, the path is left out: Pipe 'flow' failed: ….
• Whether the message is caller-facing is the root fault's call, so under STRICT disclosure a caller-facing root keeps its located message and any other is redacted.
• error_category, retryable, model and provider come from the cause chain. error_domain does too, with runtime as a floor. When nothing on the chain advises an action, user_action falls back to The run failed in pipe '<code>': the message gives the cause.

A pipe that raised something that is not a Pipelex error is reported as PipelexUnexpectedError, whose message names the original exception's class.

The exception itself carries the location structurally: pipe_code is the pipe that failed and pipe_stack its path from the entry pipe. When the failure was never located, because it happened outside any pipe, or because it arrived from a remote worker as a report that already names its pipe, pipe_code is the entry pipe and pipe_stack is empty, and the report is taken as it is. A run therefore gives the same report whether it ran in process or on a remote worker.

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