cilium/cilium · error

failed to apply option: %w

Error message

failed to apply option: %w

What it means

NewLocalServer applies each observeroption.Option to the opts struct and aborts construction if any option returns an error, wrapping it with "failed to apply option". This surfaces invalid or conflicting server options (e.g. invalid MaxFlows, bad flow buffer settings) before the local Hubble observer server is created.

Source

Thrown at pkg/hubble/observer/local_observer.go:83

	// numObservedFlows counts how many flows have been observed
	numObservedFlows atomic.Uint64

	nsManager namespace.Manager
}

// NewLocalServer returns a new local observer server.
func NewLocalServer(
	payloadParser parser.Decoder,
	nsManager namespace.Manager,
	logger *slog.Logger,
	options ...observeroption.Option,
) (*LocalObserverServer, error) {
	opts := observeroption.Default // start with defaults
	options = append(options, DefaultOptions...)
	for _, opt := range options {
		if err := opt(&opts); err != nil {
			return nil, fmt.Errorf("failed to apply option: %w", err)
		}
	}

	logger.Info(
		"Configuring Hubble server",
		logfields.MaxFlows, opts.MaxFlows,
		logfields.EventQueueSize, opts.MonitorBuffer,
	)

	s := &LocalObserverServer{
		log:           logger,
		ring:          container.NewRing(opts.MaxFlows),
		events:        make(chan *observerTypes.MonitorEvent, opts.MonitorBuffer),
		stopped:       make(chan struct{}),
		payloadParser: payloadParser,
		startTime:     time.Now(),
		nsManager:     nsManager,
		opts:          opts,

View on GitHub (pinned to ac7b90affa)

Solutions

1. Fix the underlying option that returned the error (inspect the wrapped cause via %w / errors.Unwrap).
2. Validate option values (e.g. MaxFlows > 0) before passing them to NewLocalServer.
3. If defaults are implicated, pass explicit valid options to override them.

Example fix

// before
server, err := observer.NewLocalServer(log, nil, observeroption.WithMaxFlows(-1))
// after
server, err := observer.NewLocalServer(log, nil, observeroption.WithMaxFlows(4095))

if maxFlows <= 0 { return errors.New("maxFlows must be positive") }

srv, err := observer.NewLocalServer(log, ring, opts...)
if err != nil {
    return nil, fmt.Errorf("hubble local server init: %w", err)
}

When it happens

Trigger: Passing an observeroption.Option whose func returns an error into NewLocalServer — commonly a custom Option setting an invalid MaxFlows or other invalid configuration value.

Common situations: Custom option functions with flawed validation, tests injecting bad options, default options failing after a library upgrade changed validation rules.

Related errors

• lost event send interval must be greater than 0
• certificate and private key are both required, but only one
• transport layer security required
• config file undefined
• no listener configured

AI-assisted analysis of cilium/cilium@ac7b90affa (2026-08-31). Data as JSON: /api/errors/62a5ba7182eeb5d4. Report an issue: GitHub.