logger

Overview ¶

Package logger provides context-scoped structured logging for Genkit.

This package wraps the standard library's log/slog package to provide context-aware logging throughout Genkit operations. Logs are automatically associated with the current action or flow context.

Usage ¶

Retrieve the logger from context within action or flow handlers:

func myFlow(ctx context.Context, input string) (string, error) {
	log := logger.FromContext(ctx)

	log.Info("Processing input", "size", len(input))
	log.Debug("Input details", "value", input)

	result, err := process(input)
	if err != nil {
		log.Error("Processing failed", "error", err)
		return "", err
	}

	log.Info("Processing complete", "resultSize", len(result))
	return result, nil
}

Log Levels ¶

Control the global log level to filter output:

// Show debug logs (verbose)
logger.SetLevel(slog.LevelDebug)

// Show info and above (default)
logger.SetLevel(slog.LevelInfo)

// Show only warnings and errors
logger.SetLevel(slog.LevelWarn)

// Show only errors
logger.SetLevel(slog.LevelError)

// Get the current log level
level := logger.GetLevel()

Context Integration ¶

The logger is automatically available in action and flow contexts. It inherits from the context passed to [genkit.Init] and flows through all nested operations.

For custom operations outside of actions/flows, attach a logger to context:

log := slog.Default()
ctx = logger.WithContext(ctx, log)

slog Compatibility ¶

The logger returned by FromContext is a standard *slog.Logger and supports all slog methods:

log := logger.FromContext(ctx)

// Structured logging with attributes
log.Info("User action",
	"userId", userID,
	"action", "login",
	"duration", elapsed,
)

// Grouped attributes
log.Info("Request completed",
	slog.Group("request",
		"method", r.Method,
		"path", r.URL.Path,
	),
	slog.Group("response",
		"status", status,
		"bytes", written,
	),
)

// With pre-set attributes
requestLog := log.With("requestId", requestID)
requestLog.Info("Starting")
// ... later ...
requestLog.Info("Finished")

This package is primarily used by Genkit internals but is useful for plugin developers who need consistent logging that integrates with Genkit's observability features.

Package logger provides a context-scoped slog.Logger.