Merge pull request #753 from stvales/start-stop

Problem: Rapid zyre start/stop may create a hello/goodbye storm between peers

Author: sphaero

src/zyre_node.c

@@ -1082,10 +1082,18 @@ zyre_node_recv_peer (zyre_node_t *self)
     zyre_peer_t *peer = (zyre_peer_t *) zhash_lookup (self->peers, zuuid_str (uuid));
     if (zre_msg_id (msg) == ZRE_MSG_HELLO) {
         if (peer) {
-            //  Remove fake peers
+            //  ignore already existing peers
             if (zyre_peer_ready (peer)) {
-                zyre_node_remove_peer (self, peer);
-                assert (!(zyre_peer_t *) zhash_lookup (self->peers, zuuid_str (uuid)));
+                /*
+                 NB: we ignore peer here instead of destroying due to possible erroneous
+                 destruction in case of rapid deconnection/reconnection of our node, (e.g.,
+                 when wrongly using zyre_start/zyre_stop), in which case the ZRE_MSG_HELLO
+                 may be received twice from other peers and subsequent peers removal would
+                 provoke a HELLO/GOODBYE storm with the erroneously destroyed peers.
+                 In the case of a peer reconnecting with the same endpoint and the previous
+                 one being non-responsive, ping mechanism will take care of cleaning it.
+                 */
+                return;
             }
             else
             if (streq (zyre_peer_endpoint (peer), self->endpoint)) {