clonesrv5.java

package guide;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.zeromq.SocketType;
import org.zeromq.ZContext;
import org.zeromq.ZLoop;
import org.zeromq.ZLoop.IZLoopHandler;
import org.zeromq.ZMQ;
import org.zeromq.ZMQ.PollItem;
import org.zeromq.ZMQ.Socket;

//  Clone server - Model Five
public class clonesrv5
{
    private final ZContext           ctx;       //  Context wrapper
    private final Map<String, kvmsg> kvmap;     //  Key-value store
    private final ZLoop              loop;      //  zloop reactor
    private long               sequence;  //  How many updates we're at
    private final Socket             snapshot;  //  Handle snapshot requests
    private final Socket             publisher; //  Publish updates to clients
    private final Socket             collector; //  Collect updates from clients

    //  .split snapshot handler
    //  This is the reactor handler for the snapshot socket; it accepts
    //  just the ICANHAZ? request and replies with a state snapshot ending
    //  with a KTHXBAI message:
    private static class Snapshots implements IZLoopHandler
    {
        @Override
        public int handle(ZLoop loop, PollItem item, Object arg)
        {
            clonesrv5 srv = (clonesrv5) arg;
            Socket socket = item.getSocket();

            byte[] identity = socket.recv();
            if (identity != null) {
                //  Request is in second frame of message
                String request = socket.recvStr();
                String subtree = null;
                if (request.equals("ICANHAZ?")) {
                    subtree = socket.recvStr();
                }
                else System.out.print("E: bad request, aborting\n");

                if (subtree != null) {
                    //  Send state socket to client
                    for (Entry<String, kvmsg> entry : srv.kvmap.entrySet()) {
                        sendSingle(entry.getValue(), identity, subtree, socket);
                    }

                    //  Now send END message with getSequence number
                    System.out.printf("I: sending shapshot=%d\n", srv.sequence);
                    socket.send(identity, ZMQ.SNDMORE);
                    kvmsg kvmsg = new kvmsg(srv.sequence);
                    kvmsg.setKey("KTHXBAI");
                    kvmsg.setBody(subtree.getBytes(ZMQ.CHARSET));
                    kvmsg.send(socket);
                    kvmsg.destroy();
                }
            }
            return 0;
        }
    }

    //  .split collect updates
    //  We store each update with a new getSequence number, and if necessary, a
    //  time-to-live. We publish updates immediately on our publisher socket:
    private static class Collector implements IZLoopHandler
    {
        @Override
        public int handle(ZLoop loop, PollItem item, Object arg)
        {
            clonesrv5 srv = (clonesrv5) arg;
            Socket socket = item.getSocket();

            kvmsg msg = kvmsg.recv(socket);
            if (msg != null) {
                msg.setSequence(++srv.sequence);
                msg.send(srv.publisher);
                int ttl = Integer.parseInt(msg.getProp("ttl"));
                if (ttl > 0)
                    msg.setProp("ttl", "%d", System.currentTimeMillis() + ttl * 1000);
                msg.store(srv.kvmap);
                System.out.printf("I: publishing update=%d\n", srv.sequence);
            }

            return 0;
        }
    }

    private static class FlushTTL implements IZLoopHandler
    {
        @Override
        public int handle(ZLoop loop, PollItem item, Object arg)
        {
            clonesrv5 srv = (clonesrv5) arg;
            if (srv.kvmap != null) {
                for (kvmsg msg : new ArrayList<>(srv.kvmap.values())) {
                    srv.flushSingle(msg);
                }
            }
            return 0;
        }
    }

    public clonesrv5()
    {
        //  Main port we're working on
        int port = 5556;
        ctx = new ZContext();
        kvmap = new HashMap<>();
        loop = new ZLoop(ctx);
        loop.verbose(false);

        //  Set up our clone server sockets
        snapshot = ctx.createSocket(SocketType.ROUTER);
        snapshot.bind(String.format("tcp://*:%d", port));
        publisher = ctx.createSocket(SocketType.PUB);
        publisher.bind(String.format("tcp://*:%d", port + 1));
        collector = ctx.createSocket(SocketType.PULL);
        collector.bind(String.format("tcp://*:%d", port + 2));
    }

    public void run()
    {
        //  Register our handlers with reactor
        PollItem poller = new PollItem(snapshot, ZMQ.Poller.POLLIN);
        loop.addPoller(poller, new Snapshots(), this);
        poller = new PollItem(collector, ZMQ.Poller.POLLIN);
        loop.addPoller(poller, new Collector(), this);
        loop.addTimer(1000, 0, new FlushTTL(), this);

        loop.start();
        loop.destroy();
        ctx.destroy();
    }

    //  We call this function for each getKey-value pair in our hash table
    private static void sendSingle(kvmsg msg, byte[] identity, String subtree, Socket socket)
    {
        if (msg.getKey().startsWith(subtree)) {
            socket.send(identity, //  Choose recipient
                    ZMQ.SNDMORE);
            msg.send(socket);
        }
    }

    //  .split flush ephemeral values
    //  At regular intervals, we flush ephemeral values that have expired. This
    //  could be slow on very large data sets:

    //  If getKey-value pair has expired, delete it and publish the
    //  fact to listening clients.
    private void flushSingle(kvmsg msg)
    {
        long ttl = Long.parseLong(msg.getProp("ttl"));
        if (ttl > 0 && System.currentTimeMillis() >= ttl) {
            msg.setSequence(++sequence);
            msg.setBody(ZMQ.MESSAGE_SEPARATOR);
            msg.send(publisher);
            msg.store(kvmap);
            System.out.printf("I: publishing delete=%d\n", sequence);
        }
    }

    public static void main(String[] args)
    {
        clonesrv5 srv = new clonesrv5();
        srv.run();
    }
}