// The main task is an LRU queue with heartbeating on workers so we can
// detect crashed or blocked worker tasks:
public static void main(final String[] args) {
final ZContext ctx = new ZContext();
final Socket frontend = ctx.createSocket(ZMQ.ROUTER);
final Socket backend = ctx.createSocket(ZMQ.ROUTER);
frontend.bind("tcp://*:5555"); // For clients
backend.bind("tcp://*:5556"); // For workers
// List of available workers
final ArrayList<Worker> workers = new ArrayList<Worker>();
// Send out heartbeats at regular intervals
long heartbeat_at = System.currentTimeMillis() + HEARTBEAT_INTERVAL;
while (true) {
final PollItem items[] = {
new PollItem(backend, ZMQ.Poller.POLLIN), new PollItem(frontend, ZMQ.Poller.POLLIN)
};
// Poll frontend only if we have available workers
final int rc = ZMQ.poll(items, workers.size() > 0 ? 2 : 1, HEARTBEAT_INTERVAL);
if (rc == -1) {
break; // Interrupted
}
// Handle worker activity on backend
if (items[0].isReadable()) {
// Use worker address for LRU routing
final ZMsg msg = ZMsg.recvMsg(backend);
if (msg == null) {
break; // Interrupted
}
// Any sign of life from worker means it's ready
final ZFrame address = msg.unwrap();
final Worker worker = new Worker(address);
worker.ready(workers);
// Validate control message, or return reply to client
if (msg.size() == 1) {
final ZFrame frame = msg.getFirst();
final String data = new String(frame.getData());
if (!data.equals(PPP_READY) && !data.equals(PPP_HEARTBEAT)) {
System.out.println("E: invalid message from worker");
msg.dump(System.out);
}
msg.destroy();
} else {
msg.send(frontend);
}
}
if (items[1].isReadable()) {
// Now get next client request, route to next worker
final ZMsg msg = ZMsg.recvMsg(frontend);
if (msg == null) {
break; // Interrupted
}
msg.push(Worker.next(workers));
msg.send(backend);
}
// We handle heartbeating after any socket activity. First we send
// heartbeats to any idle workers if it's time. Then we purge any
// dead workers:
if (System.currentTimeMillis() >= heartbeat_at) {
for (final Worker worker : workers) {
worker.address.send(backend, ZFrame.REUSE + ZFrame.MORE);
final ZFrame frame = new ZFrame(PPP_HEARTBEAT);
frame.send(backend, 0);
}
heartbeat_at = System.currentTimeMillis() + HEARTBEAT_INTERVAL;
}
Worker.purge(workers);
}
// When we're done, clean up properly
while (workers.size() > 0) {
final Worker worker = workers.remove(0);
}
workers.clear();
ctx.destroy();
}
// The main task begins by setting-up all its sockets. The local frontend
// talks to clients, and our local backend talks to workers. The cloud
// frontend talks to peer brokers as if they were clients, and the cloud
// backend talks to peer brokers as if they were workers. The state
// backend publishes regular state messages, and the state frontend
// subscribes to all state backends to collect these messages. Finally,
// we use a PULL monitor socket to collect printable messages from tasks:
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: peering3 me {you}");
System.exit(-1);
}
self = argv[0];
System.out.printf("I: preparing broker at %s\n", self);
Random rand = new Random(System.nanoTime());
ZContext ctx = new ZContext();
// Prepare local frontend and backend
Socket localfe = ctx.createSocket(ZMQ.ROUTER);
localfe.bind(String.format("ipc://%s-localfe.ipc", self));
Socket localbe = ctx.createSocket(ZMQ.ROUTER);
localbe.bind(String.format("ipc://%s-localbe.ipc", self));
// Bind cloud frontend to endpoint
Socket cloudfe = ctx.createSocket(ZMQ.ROUTER);
cloudfe.setIdentity(self.getBytes());
cloudfe.bind(String.format("ipc://%s-cloud.ipc", self));
// Connect cloud backend to all peers
Socket cloudbe = ctx.createSocket(ZMQ.ROUTER);
cloudbe.setIdentity(self.getBytes());
int argn;
for (argn = 1; argn < argv.length; argn++) {
String peer = argv[argn];
System.out.printf("I: connecting to cloud forintend at '%s'\n", peer);
cloudbe.connect(String.format("ipc://%s-cloud.ipc", peer));
}
// Bind state backend to endpoint
Socket statebe = ctx.createSocket(ZMQ.PUB);
statebe.bind(String.format("ipc://%s-state.ipc", self));
// Connect statefe to all peers
Socket statefe = ctx.createSocket(ZMQ.SUB);
statefe.subscribe("".getBytes());
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));
}
// Prepare monitor socket
Socket monitor = ctx.createSocket(ZMQ.PULL);
monitor.bind(String.format("ipc://%s-monitor.ipc", self));
// Start local workers
int worker_nbr;
for (worker_nbr = 0; worker_nbr < NBR_WORKERS; worker_nbr++) new worker_task().start();
// Start local clients
int client_nbr;
for (client_nbr = 0; client_nbr < NBR_CLIENTS; client_nbr++) new client_task().start();
// Queue of available workers
int localCapacity = 0;
int cloudCapacity = 0;
ArrayList<ZFrame> workers = new ArrayList<ZFrame>();
// The main loop has two parts. First we poll workers and our two service
// sockets (statefe and monitor), in any case. If we have no ready workers,
// there's no point in looking at incoming requests. These can remain on
// their internal 0MQ queues:
while (true) {
// First, route any waiting replies from workers
PollItem primary[] = {
new PollItem(localbe, Poller.POLLIN),
new PollItem(cloudbe, Poller.POLLIN),
new PollItem(statefe, Poller.POLLIN),
new PollItem(monitor, Poller.POLLIN)
};
// If we have no workers anyhow, wait indefinitely
int rc = ZMQ.poll(primary, localCapacity > 0 ? 1000 : -1);
if (rc == -1) break; // Interrupted
// Track if capacity changes during this iteration
int previous = localCapacity;
// Handle reply from local worker
ZMsg msg = null;
if (primary[0].isReadable()) {
msg = ZMsg.recvMsg(localbe);
if (msg == null) break; // Interrupted
ZFrame address = msg.unwrap();
workers.add(address);
localCapacity++;
// If it's READY, don't route the message any further
ZFrame frame = msg.getFirst();
if (new String(frame.getData()).equals(WORKER_READY)) {
msg.destroy();
msg = null;
}
}
// Or handle reply from peer broker
else if (primary[1].isReadable()) {
msg = ZMsg.recvMsg(cloudbe);
if (msg == null) break; // Interrupted
// We don't use peer broker address for anything
ZFrame address = msg.unwrap();
address.destroy();
}
// Route reply to cloud if it's addressed to a broker
for (argn = 1; msg != null && argn < argv.length; argn++) {
byte[] data = msg.getFirst().getData();
if (argv[argn].equals(new String(data))) {
msg.send(cloudfe);
msg = null;
}
}
// Route reply to client if we still need to
if (msg != null) msg.send(localfe);
// If we have input messages on our statefe or monitor sockets we
// can process these immediately:
if (primary[2].isReadable()) {
String peer = statefe.recvStr();
String status = statefe.recvStr();
cloudCapacity = Integer.parseInt(status);
}
if (primary[3].isReadable()) {
String status = monitor.recvStr();
System.out.println(status);
}
// Now we route as many client requests as we have worker capacity
// for. We may reroute requests from our local frontend, but not from //
// the cloud frontend. We reroute randomly now, just to test things
// out. In the next version we'll do this properly by calculating
// cloud capacity://
while (localCapacity + cloudCapacity > 0) {
PollItem secondary[] = {
new PollItem(localfe, Poller.POLLIN), new PollItem(cloudfe, Poller.POLLIN)
};
if (localCapacity > 0) rc = ZMQ.poll(secondary, 2, 0);
else rc = ZMQ.poll(secondary, 1, 0);
assert (rc >= 0);
if (secondary[0].isReadable()) {
msg = ZMsg.recvMsg(localfe);
} else if (secondary[1].isReadable()) {
msg = ZMsg.recvMsg(cloudfe);
} else break; // No work, go back to backends
if (localCapacity > 0) {
ZFrame frame = workers.remove(0);
msg.wrap(frame);
msg.send(localbe);
localCapacity--;
} else {
// Route to random broker peer
int random_peer = rand.nextInt(argv.length - 1) + 1;
msg.push(argv[random_peer]);
msg.send(cloudbe);
}
}
// We broadcast capacity messages to other peers; to reduce chatter
// we do this only if our capacity changed.
if (localCapacity != previous) {
// We stick our own address onto the envelope
statebe.sendMore(self);
// Broadcast new capacity
statebe.send(String.format("%d", localCapacity), 0);
}
}
// When we're done, clean up properly
while (workers.size() > 0) {
ZFrame frame = workers.remove(0);
frame.destroy();
}
ctx.destroy();
}