Environment

The Reactor Environment

Before you can do anything useful with Reactor, you need to create a long-lived Environment instance which holds the configured Dispatchers and properties that influence how Reactor components behave. Each instance of an Environment will contain its own set of Dispatchers, so be careful how many instances of these you create. If possible, only one instance per JVM is recommended.

Create a new Environment using the default properties file configuration reader, which reads the configuration from META-INF/reactor/default.properties:

Environment env = new Environment();

When you create Reactors, Streams, Promises, and other components that require a Dispatcher, pass this Environment instance to the Spec for that component. For example, to reference this Environment when creating Reactors:

Reactor r = Reactors.reactor()
  .env(env)
  .get();

Dispatchers

There are a default set of Dispatchers created and they should cover the majority of use cases. But it might be the case that you don’t need a particular type of Dispatcher at all (say you’re only using the RingBufferDispatcher) so you want to prevent that type of Dispatcher from being configured. You’d simply make a copy of the Reactor default.properties and set the .type of the Dispatcher you want to turn off to a blank.

By default, a ThreadPoolExecutorDispatcher is configured.

reactor.dispatchers.threadPoolExecutor.type = threadPoolExecutor
reactor.dispatchers.threadPoolExecutor.size = 0
# Backlog is how many Task objects to warm up internally
reactor.dispatchers.threadPoolExecutor.backlog = 1024

If you don’t need this Dispatcher, then set the property reactor.dispatchers.threadPoolExecutor.type to a blank:

reactor.dispatchers.threadPoolExecutor.type =

Profiles

If you don’t want to change the default properties you can activate a "profile". To activate a profile named "testing", create a properties file called META-INF/reactor/testing.properties. When you run your Reactor application, activate the profile by referencing it in the reactor.profiles.active System property:

$ java -Dreactor.profiles.active=testing -jar reactor-app-1.0.jar

If you don’t want Reactor’s default properties to be read at all, create a .properties file with the configuration you want and set the system property reactor.profiles.default to the name of the profile you want to load as the "default" profile. For example, to use the "production" profile as the default, create a properties file called META-INF/reactor/production.properties. When running your Reactor application, set the reactor.profiles.default System property to "production":

$ java -Dreactor.profiles.default=production -jar reactor-app-1.0.jar

The Default Dispatcher

When creating components that need Dispatchers, unless you specify a particular Dispatcher to use, Reactor will give your component the "default" Dispatcher. In its default configuration, that would be the "ringBuffer" Dispatcher. To change that, set the System property reactor.dispatchers.default to the name of the Dispatcher to be considered the default:

# change to the eventLoop for a default Dispatcher
reactor.dispatchers.default = eventLoop