Lifecycle implementation

Orleans composes many independently registered services into one silo or client. Some services must start only after a dependency is ready and stop before that dependency disappears. The lifecycle abstraction gives those components an ordered protocol without placing every dependency in a central start method.

Observable and observers

ILifecycleObservable accepts subscriptions at integer stages. During startup it visits stages in ascending order; during shutdown it visits them in descending order. Every observer at a stage completes before the lifecycle advances.

ILifecycleObserver provides asynchronous OnStart and OnStop callbacks. ILifecycleParticipant<T> is the discovery contract used by dependency injection: a participant receives the lifecycle and subscribes itself.

Rendering diagram.

The reverse shutdown order is the key invariant. A service can continue using dependencies which started at earlier stages until its own stop callback completes.

Silo and client lifecycles

SiloLifecycleSubject drives silo startup and shutdown. Membership, messaging, grain directory, activation collection, statistics, providers, and other runtime components participate at named ServiceLifecycleStage values.

The client uses the same pattern for gateway discovery, connections, stream providers, and the outside runtime client. The generic ILifecycleObservable also lets providers compose a private lifecycle when the silo-specific interface is unnecessary.

The host-facing stage list and configuration examples are documented in silo lifecycle. This page focuses on the protocol rather than where application startup code should be registered.

Subscription rules

A lifecycle participant should:

• subscribe during composition, before lifecycle start;
• use a stable observer name for diagnostics;
• select the latest stage whose prerequisites are guaranteed;
• make OnStop safe after a partial OnStart;
• honor the supplied cancellation token; and
• release dependencies before their lower stage stops.

Avoid creating hidden ordering by resolving and starting another participant manually. Stage dependencies should remain visible in lifecycle subscriptions.

Failure behavior

Startup does not skip a failed observer and continue to a success-shaped state. The exception aborts lifecycle progress and the host reports startup failure. Shutdown attempts to unwind initialized stages under its cancellation deadline.

Cancellation bounds lifecycle observation; it cannot guarantee instantaneous cleanup of external resources. Provider code should keep shutdown idempotent and should not swallow failures which leave durable ownership ambiguous.

Source

• LifecycleSubject implements stage traversal; see its implementation.
• SiloLifecycleSubject is the silo lifecycle; see its implementation.
• DefaultSiloServices shows participant registration.
• PersistentStreamProvider is a named-provider example with separate initialize and active stages; see its lifecycle participation implementation.