Disco

Simple zookeeper-based service discovery.

Requirements

• Java 1.7
• Zookeeper 3.4.5+

This library uses Zookeeper nodes to maintain a set of available hosts for a configured service. A client is automatically updated by Zookeeper/Curator when a service is added or removed.

Client usage

The server allows you to save arbitrary data per node that is accessible from the client via the Decoder<T> interface.

CuratorFramework framework; // Initialize this
SelectorStrategy selector = new RoundRobinSelectorStrategy();
Decoder<T> decoder; // Initialize this
DiscoClient<> client = new DiscoClient<T>(framework, serviceName, selector, decoder);
client.start(host, port);

Optional<Node<T>> node = client.getServiceNode();

Based on the selector strategy, the service will return the nodename of a connected service, or Optional.absent() if none are connected.

Stop the client on shutdown to cleanly disconnect from Zookeeper.

client.stop();

Service usage

CuratorFramework framework; // Initialize this
byte[] payload; // Initialize this
DiscoService service = new DiscoService(framework, "myservice");
service.start("hostname", 4321, true, payload);

As long as the service is running, this configuration will be associated with the Zookeeper node /services/myservice/nodes/hostname:4321 and the byte[] payload as the node's data. Upon stopping the service, the node will be removed from Zookeeper. The third parameter dictates whether the service adds a shutdown hook to stop the disco service. This is useful because of you want to remove the service from discovery before peforming a full shutdown, for example before shutting down the HTTP port.

service.stop();

Testing

Run tests with mvn test. Note: tests assume you have Zookeeper running on localhost:2181