MXS-553: List connections in sessions resource

The connections that relate to a particular session are now a part of the
sessions resource. Currently, only the generic information is stored for
each connection (id and server name).

include/maxscale/dcb.h

@@ -400,6 +400,15 @@ int dcb_get_port(const DCB *dcb);
  */
 DCB* dcb_get_current();
 
+/**
+ * Get JSON representation of the DCB
+ *
+ * @param dcb DCB to convert to JSON
+ *
+ * @return The JSON representation
+ */
+json_t* dcb_to_json(DCB* dcb);
+
 /**
  * DCB flags values
  */

server/core/dcb.cc

@@ -3749,3 +3749,15 @@ static int downstream_throttle_callback(DCB *dcb, DCB_REASON reason, void *userd
 
     return 0;
 }
+
+json_t* dcb_to_json(DCB* dcb)
+{
+    json_t* obj = json_object();
+
+    char buf[25];
+    snprintf(buf, sizeof(buf), "%p", dcb);
+    json_object_set_new(obj, "id", json_string(buf));
+    json_object_set_new(obj, "server", json_string(dcb->server->name));
+
+    return obj;
+}

server/core/session.cc

@@ -1042,6 +1042,15 @@ json_t* session_json_data(const MXS_SESSION *session, const char *host)
         json_object_set_new(attr, "idle", json_real(idle));
     }
 
+    json_t* dcb_arr = json_array();
+
+    for (auto it = session->dcb_set->begin(); it != session->dcb_set->end(); it++)
+    {
+        json_array_append_new(dcb_arr, dcb_to_json(*it));
+    }
+
+    json_object_set_new(attr, "connections", dcb_arr);
+
     json_object_set_new(data, CN_ATTRIBUTES, attr);
     json_object_set_new(data, CN_LINKS, mxs_json_self_link(host, CN_SESSIONS, ss.str().c_str()));