[zeromq-dev] It looks like socket id's can't change with a router-router topology. Is that correct?

[Mark Wright]

I have a router-router setup (destination IDs are acquired via a
broadcast/response, similar to the Freelance pattern  in the ZMQ book).

I've noticed that if my destinations go down and come back up with a new
ID, clients can't route to that ID.  I'm using 4.0.3.

This code demonstrates the issue (on windows - although the Sleep() call is
the only platform-specific call).  It creates a client and server, sends
from client to server, stops the server and starts a new one with the same
ID, then stops the server and starts a new with (on the same port) with a
different id.  The first two sends succeed, the last one fails:

#include <zmq.h>
#include <zmq_utils.h>
#include <iostream>

int
route_send (void *socket, const char *id, const char *data)
{
  int rc = 0;

  rc = zmq_send (socket, id, strlen (id), ZMQ_SNDMORE); // server addr
  if (rc == -1)
    return 0;
  rc = zmq_send (socket, "", 0, ZMQ_SNDMORE); // null
  if (rc == -1)
    return 0;
  rc = zmq_send (socket, data, strlen (data), 0); // data
  if (rc == -1)
    return 0;

  return 1;
}

int
route_recv (void *socket)
{
  int rc = 0;

  char buf[100];

  rc = zmq_recv (socket, buf, 100, 0); // client addr
  if (rc == -1)
    return 0;
  printf ("client addr received.\n");
  rc = zmq_recv (socket, buf, 100, 0); // null
  if (rc == -1)
    return 0;
  printf ("null received.\n");
  rc = zmq_recv (socket, buf, 100, 0); // data
  if (rc == -1)
    return 0;
  buf[rc] = 0;
  printf ("data received: %s\n", buf);

  return 1;
}


int
main ()
{
  int rc = 0;

  static void *ctx = zmq_ctx_new ();

  // server 1 setup
  void *server = zmq_socket (ctx, ZMQ_ROUTER);
  rc = zmq_setsockopt (server, ZMQ_IDENTITY, "idserver0001", 12);
  rc = zmq_bind (server, "tcp://127.0.0.1:30000");
  if (rc == -1) {
    return 1;
  }

  // client setup
  void *client = zmq_socket (ctx, ZMQ_ROUTER);
  rc = zmq_setsockopt (server, ZMQ_IDENTITY, "idclient0001", 12);
  if (rc == -1)
    return 1;
  rc = zmq_connect (client, "tcp://127.0.0.1:30000");
  if (rc == -1)
    return 1;

  Sleep (50);

  printf("sending to server 1\n");
  route_send (client, "idserver0001", "test data 1");
  printf("receiving in server 1\n");
  route_recv (server);
  rc = zmq_close (server);
  if (rc == -1)
    return 1;

  // server 2 setup
  void *server2 = zmq_socket (ctx, ZMQ_ROUTER);
  rc = zmq_setsockopt (server2, ZMQ_IDENTITY, "idserver0001", 12);
  rc = zmq_bind (server2, "tcp://127.0.0.1:30000");
  if (rc == -1)
    return 1;
  Sleep (3000);

  printf("sending to server 2\n");
  route_send (client, "idserver0001", "test data 2");
  printf("receiving in server 2\n");
  route_recv (server2);
  rc = zmq_close (server2);
  if (rc == -1)
    return 1;

  // server 3 setup
  void *server3 = zmq_socket (ctx, ZMQ_ROUTER);
  rc = zmq_setsockopt (server3, ZMQ_IDENTITY, "idserver0003", 12);
  rc = zmq_bind (server3, "tcp://127.0.0.1:30000");
  if (rc == -1)
    return 1;
  Sleep (3000);

  printf("sending to server 3 i (id has changed)\n");
  route_send (client, "idserver0003", "test data 2");
  printf("receiving in server 3\n");
  route_recv (server3);
  rc = zmq_close (client);
  if (rc == -1)
    return 1;
  rc = zmq_close (server3);
  if (rc == -1)
    return 1;

  rc = zmq_close (client);
  if (rc == -1)
    return 1;
  rc = zmq_ctx_shutdown (ctx);
  if (rc == -1)
    return 1;
  rc = zmq_ctx_destroy (ctx);
  if (rc == -1)
    return 1;

  return 0;
}






-- 
Mark Wright
markscottwright at gmail.com
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