Lifecycle Management

Weaver components support the following optional lifecycle hooks:

Hook	Signature	Description
Init	Init(ctx context.Context) error	Called on component initialization; returning an error aborts startup
Start	Start(ctx context.Context) error	Called when the component starts; suitable for long-running services
Shutdown	Shutdown(ctx context.Context) error	Called on component shutdown to release resources

Init

Init is called right after the component is instantiated. Dependency injection (WithConfig, Ref) has already completed, so config and dependencies are safe to access.

Start

Components implementing Start are started concurrently before the main logic in weaver.Run runs:

func (s *serverImpl) Start(ctx context.Context) error {
    s.Logger(ctx).Info("Starting HTTP server")
    return s.server.ListenAndServe()
}

Start-phase behavior:

• All components start concurrently via an errgroup; any failure triggers overall shutdown
• Component panics are recovered and treated as start failures
• A normal return from Start means the component finished running (long-running services should block inside Start, e.g. ListenAndServe)

Shutdown

Shutdown is called:

• After the main logic returns, before weaver.Run exits — all components are shut down
• After a system signal (SIGINT / SIGQUIT / SIGTERM) cancels the context
• When a config hot reload restarts components (Shutdown first, then Start)

func (a *app) Shutdown(ctx context.Context) error {
    a.Logger(ctx).Info("App Shutdown")
    return nil
}

Signals and Graceful Exit

weaver.Run listens for SIGINT, SIGQUIT and SIGTERM via signal.NotifyContext and cancels the context on receipt.

Components can trigger graceful shutdown proactively via Exec() (equivalent to sending the process an exit signal):

func (a *app) Init(ctx context.Context) error {
    go func() {
        // when some exit condition is met
        a.Exec()
    }()
    return nil
}

Complete Flow

weaver.Run
 ├─ parse -conf / -version flags
 ├─ load config file
 ├─ instantiate the Main component (dependencies cascade)
 ├─ call Start on all components concurrently
 ├─ run the main logic app(ctx, main)
 └─ call Shutdown on all components on exit