Add support for JSON logging

cmd/topf/render.go

@@ -43,12 +43,14 @@ func newRenderCmd() *cli.Command {
 				return err
 			}
 
-			return writeMachineConfigs(nodes, c.String("output"))
+			return writeMachineConfigs(nodes, c.String("output"), t)
 		},
 	}
 }
 
-func writeMachineConfigs(nodes []*topf.Node, outputDir string) error {
+func writeMachineConfigs(nodes []*topf.Node, outputDir string, t topf.Topf) error {
+	logger := t.Logger().With("command", "render")
+
 	if err := os.MkdirAll(outputDir, 0o750); err != nil {
 		return fmt.Errorf("failed to create output directory: %w", err)
 	}
@@ -80,7 +82,7 @@ func writeMachineConfigs(nodes []*topf.Node, outputDir string) error {
 			return fmt.Errorf("failed to write config for %s: %w", node.Node.Host, err)
 		}
 
-		fmt.Fprintf(os.Stdout, "Wrote machine config for %s to %s\n", node.Node.Host, outputPath)
+		logger.Info("Wrote machine config", "node", node.Node.Host, "path", outputPath)
 	}
 
 	return errors.Join(errs...)

cmd/topf/root.go

@@ -53,6 +53,12 @@ func main() {
 				Usage:   "set the logging level (debug, info, warn, error)",
 				Sources: cli.EnvVars("LOG_LEVEL"),
 			},
+			&cli.BoolFlag{
+				Name:    "json-log",
+				Value:   false,
+				Usage:   "emit json logs instead of human readable text",
+				Sources: cli.EnvVars("TOPF_JSON_LOG"),
+			},
 			&cli.BoolFlag{
 				Name:        "redact",
 				Value:       true,
@@ -80,6 +86,7 @@ func main() {
 				ConfigPath:       c.String("topfconfig"),
 				NodesRegexFilter: c.String("nodes-filter"),
 				LogLevel:         c.String("log-level"),
+				JsonLog:          c.Bool("json-log"),
 				Redact:           c.Bool("redact"),
 				Confirm:          c.Bool("confirm"),
 				SubmitToFactory:  c.Bool("submit-to-factory"),
@@ -89,6 +96,12 @@ func main() {
 				return ctx, err
 			}
 
+			// Set the logger configured by the runtime as the default.
+			// 
+			// While commands should still use the one from the runtime,
+			// we need to have it available in the app error handler below.
+			slog.SetDefault(topf.Logger())
+
 			return context.WithValue(ctx, topfRuntimeCtxKey, topf), nil
 		},
 		Commands: []*cli.Command{
@@ -106,7 +119,7 @@ func main() {
 	}
 
 	if err := app.Run(context.Background(), os.Args); err != nil {
-		slog.Error("error", "error", err)
+		slog.Error("error", "failed to run command", err)
 		os.Exit(1)
 	}
 }

internal/topf/topf.go

@@ -84,6 +84,9 @@ type RuntimeConfig struct {
 	// LogLevel sets the logging verbosity (debug, info, warn, error)
 	LogLevel string
 
+	// Emit logs as JSON instead of human readable text
+	JsonLog bool
+
 	// Redact controls whether sensitive values are masked in output
 	Redact bool
 
@@ -138,7 +141,14 @@ func NewTopfRuntime(cfg RuntimeConfig) (Topf, error) {
 	opts := &slog.HandlerOptions{
 		Level: level,
 	}
-	handler := slog.NewTextHandler(os.Stderr, opts)
+
+	var handler slog.Handler
+	if cfg.JsonLog {
+		handler = slog.NewJSONHandler(os.Stderr, opts)
+	} else {
+		handler = slog.NewTextHandler(os.Stderr, opts)
+	}
+
 	logger := slog.New(handler)
 
 	var mw *maskedwriter.Writer