An xMsg actor is required to publish or subscribe messages. Messages are identified by topics, and contain metadata and user serialized data. Multi-threaded publication of messages is supported. Each thread must use its own connection to send messages. Subscription always runs in a background thread. Every received message is then sent to a threadpool of worker threads that run a user-defined callback for each message. This callback must be thread-safe.

A proxy must be running in order to pass messages between actors. There may be many proxies running in a xMsg cloud, but messages must be published to the same proxy than the subscription, or the subscriber will not receive them. There is no limitation on the number of proxies than an actor can be connected to.

Long-lived actors can register with a global registrar service if they are periodically publishing messages to a given topic, or subscribed to a given topic. Others actors can search the registrar to discover them, and receive or send messages to those topics.

To create an xMsg actor the following alternatives are provided:

xMsg(String name)
xMsg(String name, int poolSize)
xMsg(String name, xMsgRegAddress defaultRegistrar)
xMsg(String name, xMsgRegAddress defaultRegistrar, int poolSize)
xMsg(String name, xMsgProxyAddress defaultProxy,
     xMsgRegAddress defaultRegistrar, int poolSize)

The constructor sets the name of the actor (used for registration) and also generates a unique ID (to receive sync-publication responses). The default registrar and default proxy addresses are optional (if not given localhost and standard xMsg port are used). The default proxy address should be used for long-running publication or subscription of messages. The actor can then register as a publisher or subscriber on the default registrar service. The poolsize controls how many threads will run subscription callbacks.

The constructor will also create a connection pool to manage connections, a threadpool to process subscribed messages (using poolSize threads), and a poller thread to receive sync-publication responses.

The xMsg class implements the AutoCloseable interface. Closing the actor will close all connections, stop all subscriptions and shutdown the callback threadpool.

try (xMsg actor = new xMsg("name")) {
    // use the actor for pub/sub communications
}