README.md

GWizard Services

Put simply, a "service" is some program logic that starts up in a separate thread. Because of this, services are started and stopped in parallel.

GWizard Services dynamically loads Guava Services and starts them with Guava ServiceManager. Other GWizard modules use this facility to run web servers, metrics servers, etc but you can also use it directly to implement Services which handle their own startup/shutdown processing and execution strategies.

See https://github.com/google/guava/wiki/ServiceExplained

Maven

Install the gwizard bom, then:

    <dependency>
        <groupId>org.gwizard</groupId>
        <artifactId>gwizard-services</artifactId>
    </dependency>

Usage

If you are simply using the other GWizard modules that depend on this module, you can ignore gwizard-services. Those other modules configure ServicesModule.

If you want to explicitly configure services, you can register them like this:

A self-contained example

Example service:

    @Singleton
    @Slf4j
    public class ExampleService extends AbstractIdleService {
        @Inject
        public ExampleService(Services services) {
            services.add(this);
        }

        @Override
        protected void startUp() throws Exception {
            log.info("This is where my service does something at startup");
        }

        @Override
        protected void shutDown() throws Exception {
            log.info("This is where my service does something at shutdown");
        }
    }

Adding a service to the injected Services object registers it. You can also add Service.Listener and ServiceManager.Listener objects.

You can obtain a guava ServiceManager directly from the injector and start it, or you can use the convenient Run object:

    Injector injector = Guice.createInjector(
        //... other modules ...
        new ServicesModule()
    );

    injector.getInstance(Run.class).start();

injector.getInstance(Run.class).start(); is effectively the same as injector.getInstance(ServiceManager.class).startAsync().awaitHealthy();

To shutdown all services:

    injector.getInstance(Run.class).stop();