//------------------------------------------------------------------------------
//if worker already present remove it and re-insert it in the right
//position
void push(Workers& workers, int id) {
Workers::iterator it = std::find_if(workers.begin(),
workers.end(),
[id](const worker_info& wi){
return wi.id() == id;
});
if(it != workers.end()) workers.erase(it);
workers.insert(worker_info(id));
}
//------------------------------------------------------------------------------
//elements are ordered from highest to lowest
//1) find the first element which has a time > expiration time
//2) remove all elements from that element to last element is set
void purge(Workers& workers, const duration& cutoff) {
typedef Workers::iterator WI;
WI start = std::find_if(
workers.begin(),
workers.end(),
[&cutoff](const worker_info& wi) {
return
std::chrono::duration_cast<std::chrono::milliseconds>(
std::chrono::steady_clock::now()
- wi.timestamp()
) > cutoff;
});
if(start == workers.end()) return;
workers.erase(start, workers.end());
}
//------------------------------------------------------------------------------
int main(int argc, char** argv) {
if(argc < 3) {
std::cout << "usage: "
<< argv[0] << " <frontend address> <backend address>"
<< std::endl;
return 0;
}
const char* FRONTEND_URI = argv[1];
const char* BACKEND_URI = argv[2];
const int MAX_REQUESTS = 100;
//create communication objects
void* context = zmq_ctx_new();
assert(context);
void* frontend = zmq_socket(context, ZMQ_ROUTER);
assert(frontend);
void* backend = zmq_socket(context, ZMQ_ROUTER);
assert(backend);
assert(zmq_bind(frontend, FRONTEND_URI) == 0);
assert(zmq_bind(backend, BACKEND_URI) == 0);
//workers ordered queue
Workers workers;
int worker_id = -1;
int client_id = -1;
int rc = -1;
std::vector< char > request(0x100, 0);
std::vector< char > reply(0x100, 0);
int serviced_requests = 0;
//loop until max requests servided
while(serviced_requests < MAX_REQUESTS) {
zmq_pollitem_t items[] = {
{backend, 0, ZMQ_POLLIN, 0},
{frontend, 0, ZMQ_POLLIN, 0}};
//remove all workers that have not been active for a
//time > expiration interval
//XXX TODO: TEST
purge(workers, EXPIRATION_INTERVAL);
//XXX
//poll for incoming requests: if no workers are available
//only poll for workers(backend) since there is no point
//in trying to service a client request without active
//workers
rc = zmq_poll(items, workers.size() > 0 ? 2 : 1,
TIMEOUT);
if(rc == -1) break;
//data from workers
if(items[0].revents & ZMQ_POLLIN) {
assert(zmq_recv(backend, &worker_id, sizeof(worker_id), 0) > 0);
assert(zmq_recv(backend, 0, 0, 0) == 0);
assert(zmq_recv(backend, &client_id, sizeof(client_id), 0) > 0);
//add worker to list of available workers
push(workers, worker_id);
assert(workers.size() > 0);
//of not a 'ready' message forward message to frontend
//workers send 'ready' messages when either
if(client_id != WORKER_READY) {
int seq_id = -1;
assert(zmq_recv(backend, 0, 0, 0) == 0);
rc = zmq_recv(backend, &seq_id, sizeof(seq_id), 0);
assert(rc > 0);
rc = zmq_recv(backend, &reply[0], reply.size(), 0);
assert(rc > 0);
zmq_send(frontend, &client_id, sizeof(client_id), ZMQ_SNDMORE);
zmq_send(frontend, 0, 0, ZMQ_SNDMORE);
zmq_send(frontend, &seq_id, sizeof(seq_id), ZMQ_SNDMORE);
zmq_send(frontend, &reply[0], rc, 0);
++serviced_requests;
}
}
//request from clients
if(items[1].revents & ZMQ_POLLIN) {
int seq_id = -1;
//receive request |client id|<null>|request id|data|
zmq_recv(frontend, &client_id, sizeof(client_id), 0);
zmq_recv(frontend, 0, 0, 0);
rc = zmq_recv(frontend, &seq_id, sizeof(seq_id), 0);
assert(rc > 0);
const int req_size = zmq_recv(frontend, &request[0],
request.size(), 0);
assert(req_size > 0);
//take worker from list and forward request to it
worker_id = pop(workers);
assert(worker_id > 0);
zmq_send(backend, &worker_id, sizeof(worker_id), ZMQ_SNDMORE);
zmq_send(backend, 0, 0, ZMQ_SNDMORE);
zmq_send(backend, &client_id, sizeof(client_id), ZMQ_SNDMORE);
zmq_send(backend, 0, 0, ZMQ_SNDMORE);
zmq_send(backend, &seq_id, sizeof(seq_id), ZMQ_SNDMORE);
zmq_send(backend, &request[0], req_size, 0);
}
const int hb = HEARTBEAT; //capturing HEARTBEAT directly generates
//a warning because the lambda function should
//not capture a variable with non-automatic
//storage
//send heartbeat request to all workers: workers reply to such request
//with a 'ready' message
std::for_each(workers.begin(),
workers.end(),
[backend, hb](const worker_info& wi) {
const int id = wi.id();
zmq_send(backend, &id,
sizeof(id), ZMQ_SNDMORE);
zmq_send(backend, 0, 0, ZMQ_SNDMORE);
zmq_send(backend, &hb, sizeof(hb), 0);
});
}
zmq_close(frontend);
zmq_close(backend);
zmq_ctx_destroy(context);
return 0;
}