IsolateIdentity class

Which isolate of the app this code is running in.

An app with AppConfig.workers greater than 1 runs the same program in several isolates. They are identical by construction, which is the point — and also the problem, because some things an app talks to identify their clients by name. A message broker that tracks unacknowledged work per consumer name will hand every worker the same name, and each worker's pending messages become invisible to the others. Telling the isolates apart requires knowing which one you are.

Statics in Dart are per-isolate. Each isolate gets its own copy of top-level and static state — nothing is shared, and there is no race to guard against. That is not a caveat, it is the whole mechanism: a static can describe "which isolate am I" precisely because every isolate has a different one. It is the same reason the private _revaliIsWorker flag in the generated server file works.

Read it from anywhere, including code that has no way to be handed configuration — an AppConfig.createBroker override, for instance, takes no arguments.

The common use is work that must happen once for the process rather than once per isolate:

@override
Future<void> configureDependencies(DI di) async {
  if (!IsolateIdentity.current.isWorker) {
    di.registerSingleton<NightlyReport>(NightlyReport()..start());
  }
}

Note that RedisBroker names its own consumers from this — appending index to the name it was given — so an app does not have to work the index into consumerName itself. Doing so anyway produces orders-1-1.

Unset, it describes the parent of a single-isolate app: index 0, not a worker, one isolate in total. So a unit test, a dart test run, or an app that never spawns workers observes something true without configuring anything, and there is no null to handle.

Constructors

Properties

Methods

Operators

Static Properties

Static Methods

Constants

isolate_identity library