peering1.java

package guide;

import java.util.Random;

import org.zeromq.SocketType;
import org.zeromq.ZContext;
import org.zeromq.ZMQ;
import org.zeromq.ZMQ.Poller;
import org.zeromq.ZMQ.Socket;

//  Broker peering simulation (part 1)
//  Prototypes the state flow

public class peering1
{

    public static void main(String[] argv)
    {
        //  First argument is this broker's name
        //  Other arguments are our peers' names
        //
        if (argv.length < 1) {
            System.out.println("syntax: peering1 me {you}\n");
            System.exit(-1);
        }
        String self = argv[0];
        System.out.printf("I: preparing broker at %s\n%n", self);
        Random rand = new Random(System.nanoTime());

        try (ZContext ctx = new ZContext()) {
            //  Bind state backend to endpoint
            Socket statebe = ctx.createSocket(SocketType.PUB);
            statebe.bind(String.format("ipc://%s-state.ipc", self));

            //  Connect statefe to all peers
            Socket statefe = ctx.createSocket(SocketType.SUB);
            statefe.subscribe(ZMQ.SUBSCRIPTION_ALL);
            int argn;
            for (argn = 1; argn < argv.length; argn++) {
                String peer = argv[argn];
                System.out.printf(
                    "I: connecting to state backend at '%s'\n", peer
                );
                statefe.connect(String.format("ipc://%s-state.ipc", peer));
            }
            //  The main loop sends out status messages to peers, and collects
            //  status messages back from peers. The zmq_poll timeout defines
            //  our own heartbeat.
            Poller poller = ctx.createPoller(1);
            poller.register(statefe, Poller.POLLIN);

            while (true) {
                //  Poll for activity, or 1 second timeout
                int rc = poller.poll(1000);
                if (rc == -1)
                    break; //  Interrupted

                //  Handle incoming status messages
                if (poller.pollin(0)) {
                    String peer_name = new String(statefe.recv(0), ZMQ.CHARSET);
                    String available = new String(statefe.recv(0), ZMQ.CHARSET);
                    System.out.printf(
                        "%s - %s workers free\n", peer_name, available
                    );
                }
                else {
                    //  Send random values for worker availability
                    statebe.send(self, ZMQ.SNDMORE);
                    statebe.send(String.format("%d", rand.nextInt(10)), 0);
                }
            }
        }
    }
}