Problem: Cannot obtain a list of all peer in one group

Solution: Add a new API call to get all peers from one group. This
requires the peer to be in that group.

api/zyre.api

@@ -42,13 +42,13 @@
     </method>
 
     <method name = "set verbose">
-        Set verbose mode; this tells the node to log all traffic as well as 
+        Set verbose mode; this tells the node to log all traffic as well as
         all major events.
     </method>
 
     <method name = "set port">
-        Set UDP beacon discovery port; defaults to 5670, this call overrides 
-        that so you can create independent clusters on the same network, for 
+        Set UDP beacon discovery port; defaults to 5670, this call overrides
+        that so you can create independent clusters on the same network, for
         e.g. development vs. production. Has no effect after zyre_start().
         <argument name = "port nbr" type = "integer" />
     </method>
@@ -90,7 +90,7 @@
     <method name = "gossip connect">
         Set-up gossip discovery of other nodes. A node may connect to multiple
         other nodes, for redundancy paths. For details of the gossip network
-        design, see the CZMQ zgossip class. 
+        design, see the CZMQ zgossip class.
         <argument name = "format" type = "format" />
     </method>
 
@@ -158,29 +158,35 @@
     </method>
 
     <method name = "peers">
-        Return zlist of current peer ids. 
+        Return zlist of current peer ids.
+        <return type = "zlist" fresh = "1" />
+    </method>
+
+    <method name = "peers by group">
+        Return zlist of current peers of this group.
+        <argument name = "name" type = "string" />
         <return type = "zlist" fresh = "1" />
     </method>
 
     <method name = "own groups">
-        Return zlist of currently joined groups. 
+        Return zlist of currently joined groups.
         <return type = "zlist" fresh = "1" />
     </method>
 
     <method name = "peer groups">
-        Return zlist of groups known through connected peers. 
+        Return zlist of groups known through connected peers.
         <return type = "zlist" fresh = "1" />
     </method>
 
     <method name = "peer address">
-        Return the endpoint of a connected peer. 
+        Return the endpoint of a connected peer.
         <argument name = "peer" type = "string" />
         <return type = "string" fresh = "1" />
     </method>
 
     <method name = "peer header value">
-        Return the value of a header of a conected peer. 
-        Returns null if peer or key doesn't exits. 
+        Return the value of a header of a conected peer.
+        Returns null if peer or key doesn't exits.
         <argument name = "peer" type = "string" />
         <argument name = "name" type = "string" />
         <return type = "string" fresh = "1" />

include/zyre.h

@@ -58,15 +58,15 @@ ZYRE_EXPORT void
     zyre_set_header (zyre_t *self, const char *name, const char *format, ...);
 
 //  *** Draft method, for development use, may change without warning ***
-//  Set verbose mode; this tells the node to log all traffic as well as 
-//  all major events.                                                   
+//  Set verbose mode; this tells the node to log all traffic as well as
+//  all major events.                                                  
 ZYRE_EXPORT void
     zyre_set_verbose (zyre_t *self);
 
 //  *** Draft method, for development use, may change without warning ***
-//  Set UDP beacon discovery port; defaults to 5670, this call overrides 
-//  that so you can create independent clusters on the same network, for 
-//  e.g. development vs. production. Has no effect after zyre_start().   
+//  Set UDP beacon discovery port; defaults to 5670, this call overrides
+//  that so you can create independent clusters on the same network, for
+//  e.g. development vs. production. Has no effect after zyre_start().  
 ZYRE_EXPORT void
     zyre_set_port (zyre_t *self, int port_nbr);
 
@@ -171,6 +171,12 @@ ZYRE_EXPORT int
 ZYRE_EXPORT zlist_t *
     zyre_peers (zyre_t *self);
 
+//  *** Draft method, for development use, may change without warning ***
+//  Return zlist of current peers of this group.
+//  Caller owns return value and must destroy it when done.
+ZYRE_EXPORT zlist_t *
+    zyre_peers_by_group (zyre_t *self, const char *name);
+
 //  *** Draft method, for development use, may change without warning ***
 //  Return zlist of currently joined groups.
 //  Caller owns return value and must destroy it when done.
@@ -190,8 +196,8 @@ ZYRE_EXPORT char *
     zyre_peer_address (zyre_t *self, const char *peer);
 
 //  *** Draft method, for development use, may change without warning ***
-//  Return the value of a header of a conected peer. 
-//  Returns null if peer or key doesn't exits.       
+//  Return the value of a header of a conected peer.
+//  Returns null if peer or key doesn't exits.      
 //  Caller owns return value and must destroy it when done.
 ZYRE_EXPORT char *
     zyre_peer_header_value (zyre_t *self, const char *peer, const char *name);

src/zyre.c

@@ -450,6 +450,22 @@ zyre_peers (zyre_t *self)
     return peers;
 }
 
+
+//  --------------------------------------------------------------------------
+//  Return zlist of current peers of this group. The caller owns this list and
+//  should destroy it when finished with it.
+
+zlist_t *
+zyre_peers_by_group (zyre_t *self, const char *group)
+{
+    zlist_t *peers;
+    zstr_sendm (self->actor, "GROUP PEERS");
+    zstr_send (self->actor, group);
+    zsock_recv (self->actor, "p", &peers);
+    return peers;
+}
+
+
 //  --------------------------------------------------------------------------
 //  Return the endpoint of a connected peer. Caller owns the string.
 

src/zyre_group.c

@@ -118,6 +118,17 @@ zyre_group_send (zyre_group_t *self, zre_msg_t **msg_p)
 }
 
 
+//  --------------------------------------------------------------------------
+//  Return zlist of peer ids currently in this group
+//  Caller owns return value and must destroy it when done.
+
+zlist_t *
+zyre_group_peers (zyre_group_t *self)
+{
+    return zhash_keys (self->peers);
+}
+
+
 //  --------------------------------------------------------------------------
 //  Self test of this class
 

src/zyre_group.h

@@ -42,6 +42,11 @@ void
 void
     zyre_group_send (zyre_group_t *self, zre_msg_t **msg_p);
 
+//  Return zlist of peer ids currently in this group
+//  Caller owns return value and must destroy it when done.
+zlist_t *
+   zyre_group_peers (zyre_group_t *self);
+
 //  Self test of this class
 ZYRE_EXPORT void
     zyre_group_test (bool verbose);

src/zyre_node.c

@@ -295,8 +295,11 @@ zyre_node_dump (zyre_node_t *self)
     zsys_info (" - peers=%zu:", zhash_size (self->peers));
     zhash_foreach (self->peers, (zhash_foreach_fn *) zyre_node_log_item, self);
 
-    zsys_info (" - groups=%zu:", zhash_size (self->own_groups));
+    zsys_info (" - own groups=%zu:", zhash_size (self->own_groups));
     zhash_foreach (self->own_groups, (zhash_foreach_fn *) zyre_node_log_item, self);
+
+    zsys_info (" - peer groups=%zu:", zhash_size (self->peer_groups));
+    zhash_foreach (self->peer_groups, (zhash_foreach_fn *) zyre_node_log_item, self);
 }
 
 
@@ -447,6 +450,17 @@ zyre_node_recv_api (zyre_node_t *self)
     if (streq (command, "PEERS"))
         zsock_send (self->pipe, "p", zhash_keys (self->peers));
     else
+    if (streq (command, "GROUP PEERS")) {
+        char *name = zmsg_popstr (request);
+        zyre_group_t *group = (zyre_group_t *) zhash_lookup (self->own_groups, name);
+        if (group)
+            zsock_send (self->pipe, "p", zyre_group_peers (group));
+        else
+            zsock_send (self->pipe, "p", NULL);
+
+        zstr_free (&name);
+    }
+    else
     if (streq (command, "PEER ENDPOINT")) {
         char *uuid = zmsg_popstr (request);
         zyre_peer_t *peer = (zyre_peer_t *) zhash_lookup (self->peers, uuid);