public ZMsg recv() {
ZMsg reply = null;
Poller items = new Poller(1);
items.register(client, Poller.POLLIN);
if (items.poll(timeout * 1000) == -1) {
return null;
}
if (items.pollin(0)) {
ZMsg msg = ZMsg.recvMsg(client, 0); // 非阻塞
if (verbose) {
log.format("I:receive reply");
msg.dump(log.out());
}
assert (msg.size() >= 4);
ZFrame empty = msg.pop();
assert (empty.getData().length == 0);
empty.destroy();
ZFrame header = msg.pop();
assert (MDP.C_CLIENT.equals(header.toString()));
header.destroy();
ZFrame replyService = msg.pop();
replyService.destroy();
reply = msg;
}
return reply;
}
/**
* 发送的消息格式： [000] [006] MDPC01 [004] echo [011] Hello world
*
* @param service
* @param request
*/
public void send(String service, ZMsg request) {
assert (request == null);
request.addFirst(service); // 在reqeust前面添加帧
request.addFirst(MDP.C_CLIENT.newFrame());
request.addFirst("");
if (verbose) {
log.format("I:send request to '%s' service.\n", service);
request.dump(log.out());
}
request.send(client);
}
// 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();
}