MSC Multi-Value Service API

In  msc

Overview

Background

Complex Injectors and Values Framework

Packages org.jboss.msc.inject and org.jboss.msc.value are over-designed.
Their usage has lead to complex code with non-trivial impact on memory.

Services Provide Single Value

This is limiting and has caused difficulties in some scenarios.

Insufficient Encapsulation

The previous API exposed state machine and implementation details.
Service objects are accessible from any other service.

Proposed API Change

New Services Configuration API

We will introduce new Multi-Value Services API that will
consist of 1 additional interface and 4 additional methods in existing API.

We will introduce org.jboss.msc.Service interface superseding existing
org.jboss.msc.service.Service interface.

We will add 4 new methods to existing API, concretely:

  • org.jboss.msc.service.ServiceTarget

    • <T> ServiceBuilder<T> addService(ServiceName)

  • org.jboss.msc.service.ServiceBuilder

    • <V> java.util.function.Supplier<V> requires(ServiceName name)

    • <V> java.util.function.Consumer<V> provides(ServiceName…​ names)

    • ServiceBuilder<T> setInstance(Service<T> service)

Old Services Configuration API

We will deprecate old Single-Value Services API, concretely:

  • all types in org.jboss.msc.inject package

  • all types in org.jboss.msc.value package

  • org.jboss.msc.service.Service interface

  • all three org.jboss.msc.service.ServiceController value retrieval methods

  • org.jboss.msc.service.BatchServiceTarget interface

  • org.jboss.msc.service.ServiceController.Substate enum

  • org.jboss.msc.service.ServiceController.Transition enum

  • all API methods with deprecated types in its signature

Examples

New API usage example:

ServiceName HTTP_CONFIG = ServiceName.of("http", "config");
ServiceName HTTP_HOST = ServiceName.of("http", "host");
ServiceName HTTP_PORT = ServiceName.of("http", "port");
ServiceName HTTP_SERVER = ServiceName.of("http", "server");
ServiceBuilder configBuilder = serviceContainer.addService(HTTP_CONFIG);
Consumer<String> hostInjector = configBuilder.provides(HTTP_HOST);
Consumer<Integer> portInjector = configBuilder.provides(HTTP_PORT);
configBuilder.setInstance(new HttpConfigService(hostInjector, portInjector));
configBuilder.install();
ServiceBuilder serverBuilder = serviceContainer.addService(HTTP_SERVER);
Supplier<String> host = serverBuilder.requires(HTTP_HOST);
Supplier<Integer> port = serverBuilder.requires(HTTP_PORT);
serverBuilder.setInstance(new HttpServer(host, port));
serverBuilder.install();

Issue Metadata

Issue

Dev Contacts

QE Contacts

Affected Projects or Components

  • All subsystems

Other Interested Projects

Requirements

Hard Requirements

  • Multiple values per service.

  • 100% API backward compatibility.

  • 100% services interoperability.

Nice-to-Have Requirements

Reduce memory consumption.

Non-Requirements

Test Plan

Ensure that the existing test suite shows no regression in both WildFly Core and WildFly projects.
Unit tests will be added to MSC project ensuring backward compatibility and new functionality.