Glossary · Automation software engineering and architecture
Fail-fast behavior
Also known as: Fail fast
German: Fail-Fast-Verhalten
In software engineering, fail-fast behavior is a design principle by which a component detects invalid states, inputs or preconditions as early as possible and stops the current operation immediately with a clear error, instead of continuing and failing later in a less predictable way.
- Software engineering
In one sentence
Fail-fast behavior stops an operation at the first sign of an invalid state or input with a clear error, instead of failing later.
Example
At startup, the edge application validates its configuration file and refuses to start with a clear message if a required PLC address is missing.
How it applies
- Engineering: Check preconditions, configuration and inputs at the boundaries of a component, using assertions and validation, and report problems with enough context to locate them. Errors caught early are cheaper to diagnose than their later consequences.
- Operation: In production systems, 'fail fast' must be combined with a defined reaction. Stopping an operation is not the same as stopping the machine; the overall system still needs a planned Fault reaction.
- Documentation: Error messages produced by fail-fast checks should be documented with their cause and remedy, especially for configuration and startup errors that commissioning engineers encounter.
Fail-fast vs. fail-safe
Fail-fast is a software design principle about detecting errors early. Fail-safe behavior is a system property: on failure, the system goes to a state in which no hazard arises. Failing fast can support fail-safe behavior, but an immediate abort is not automatically safe; a machine may need a controlled stop instead. See also Graceful degradation, which keeps partial service after a fault.