Fail startup on an unparseable RETENTION_SWEEP_INTERVAL

internal/config/config.go

@@ -106,19 +106,26 @@ func envInt(key string, defaultValue int) int {
 
 // envDuration returns the value of the named environment variable
 // parsed as a Go duration (e.g. "1h", "30m"). Returns defaultValue if
-// not set or unparseable.
+// not set. If the variable is set but cannot be parsed, it returns a
+// wrapped error naming the key and the bad value, so startup fails
+// loudly rather than silently falling back to the default.
 func envDuration(
 	key string,
 	defaultValue time.Duration,
-) time.Duration {
-	if v := os.Getenv(key); v != "" {
-		d, err := time.ParseDuration(v)
-		if err == nil {
-			return d
-		}
+) (time.Duration, error) {
+	v := os.Getenv(key)
+	if v == "" {
+		return defaultValue, nil
 	}
 
-	return defaultValue
+	d, err := time.ParseDuration(v)
+	if err != nil {
+		return 0, fmt.Errorf(
+			"invalid duration for %s: %q: %w", key, v, err,
+		)
+	}
+
+	return d, nil
 }
 
 // New creates a Config by reading environment variables.
@@ -144,22 +151,30 @@ func New(lc fx.Lifecycle, params ConfigParams) (*Config, error) {
 		)
 	}
 
+	// Parse the retention sweep interval; a set-but-unparseable value
+	// is a hard error so fx aborts startup rather than silently using
+	// the default.
+	retentionSweepInterval, err := envDuration(
+		"RETENTION_SWEEP_INTERVAL",
+		defaultRetentionSweepInterval,
+	)
+	if err != nil {
+		return nil, err
+	}
+
 	// Load configuration values from environment variables
 	s := &Config{
-		DataDir:         envString("DATA_DIR"),
-		Debug:           envBool("DEBUG", false),
-		MaintenanceMode: envBool("MAINTENANCE_MODE", false),
-		Environment:     environment,
-		MetricsUsername: envString("METRICS_USERNAME"),
-		MetricsPassword: envString("METRICS_PASSWORD"),
-		Port:            envInt("PORT", defaultPort),
-		SentryDSN:       envString("SENTRY_DSN"),
-		RetentionSweepInterval: envDuration(
-			"RETENTION_SWEEP_INTERVAL",
-			defaultRetentionSweepInterval,
-		),
-		log:    log,
-		params: &params,
+		DataDir:                envString("DATA_DIR"),
+		Debug:                  envBool("DEBUG", false),
+		MaintenanceMode:        envBool("MAINTENANCE_MODE", false),
+		Environment:            environment,
+		MetricsUsername:        envString("METRICS_USERNAME"),
+		MetricsPassword:        envString("METRICS_PASSWORD"),
+		Port:                   envInt("PORT", defaultPort),
+		SentryDSN:              envString("SENTRY_DSN"),
+		RetentionSweepInterval: retentionSweepInterval,
+		log:                    log,
+		params:                 &params,
 	}
 
 	// Set default DataDir. All SQLite databases (main application