Companion

The modules' classifiers, then the built-in one: no application's, as the test DSL classifies.

The classifiers of the modules on the classpath (ServiceLoader, from a module's META-INF/services/me.ahoo.wow.spi.subscription.FailureClassifier), as StoreProviders and TransportProviders are found: each knows the raw failures of its own technology that an application's handler meets (a JDBC driver's in wow-postgres, the JDK's network failures in wow-client), in the order of their class names.

The modules' classifiers classLoader finds, as MODULES are found.

The application's classifiers, then the modules', then the caller's own (the runtime's), then the built-in one: the first that knows a failure decides.

The wait failure asks for before a retry, the server's Retry-After (WowProblemException.retryAfter), from it or the first of its causes that gives one; null when none does.