io.scalecube.examples.ClusterMetadataExample Maven / Gradle / Ivy
package io.scalecube.examples;
import io.scalecube.cluster.Cluster;
import io.scalecube.cluster.ClusterImpl;
import io.scalecube.cluster.ClusterMessageHandler;
import io.scalecube.cluster.Member;
import io.scalecube.cluster.transport.api.Message;
import java.util.Collections;
import java.util.Optional;
import java.util.concurrent.TimeUnit;
/**
* Using Cluster metadata: metadata is set of custom parameters that may be used by application
* developers to attach additional business information and identifications to cluster members.
*
* in this example we see how to attach logical name to a cluster member we nick name Joe
*
* @author ronen_h, Anton Kharenko
*/
public class ClusterMetadataExample {
/** Main method. */
public static void main(String[] args) throws Exception {
// Start seed cluster member Alice
Cluster alice = new ClusterImpl().startAwait();
// Join Joe to cluster with metadata and listen for incoming messages and print them to stdout
//noinspection unused
Cluster joe =
new ClusterImpl()
.config(opts -> opts.metadata(Collections.singletonMap("name", "Joe")))
.membership(opts -> opts.seedMembers(alice.address()))
.handler(
cluster -> {
//noinspection CodeBlock2Expr
return new ClusterMessageHandler() {
@Override
public void onMessage(Message message) {
System.out.println("joe.listen(): " + message.data());
}
};
})
.startAwait();
// Scan the list of members in the cluster and find Joe there
Optional joeMemberOptional = alice.otherMembers().stream().findAny();
System.err.println("### joeMemberOptional: " + joeMemberOptional);
System.err.println("### joeMetadata: " + alice.metadata(joeMemberOptional.get()));
// Send hello to Joe
joeMemberOptional.ifPresent(
member ->
alice
.send(member, Message.withData("Hello Joe").build())
.subscribe(
null,
ex -> {
// no-op
}));
TimeUnit.SECONDS.sleep(3);
}
}