loggnivåers

Loggnivåer, or log levels, are a standard concept in software logging used to categorize the severity or importance of individual log messages. They enable filtering and control over which messages are recorded or displayed, allowing developers and operators to adjust verbosity without changing application code. By assigning a level to each message, systems can suppress low-importance output in production while preserving detailed information for debugging during development or incidents.

Common levels typically include: TRACE (very detailed execution traces, usually for developers during debugging), DEBUG (useful for diagnosing problems and understanding behavior), INFO (informational messages about normal operation), WARN (potential issues that merit attention but do not stop execution), ERROR (errors that affect a specific operation or component), and FATAL or CRITICAL (severe failures likely to prevent further execution). Some ecosystems also use equivalents like NOTICE or INFO in slightly different ways.

Usage and best practices emphasize setting a sensible default level (often INFO or WARN in production) and adjusting verbosity by environment or configuration. Developers should avoid logging sensitive data, limit overly verbose output in production, and prefer structured logging formats that facilitate searching and analysis. Good practice also includes using hierarchical loggers and meaningful logger names to reflect components or modules, so that a single level change can affect a whole subsystem.

Implementation varies by language and framework, but most provide level-based filtering, configurable sinks, and support for rotating or rotating and archiving logs. For example, Python's standard logging defines DEBUG, INFO, WARNING, ERROR, and CRITICAL, while Java's log4j2 includes TRACE through FATAL. Though names and exact semantics differ, the core idea remains: log levels help manage visibility, performance, and operational insight.