I'll try to be as clear as possible. I've got two classes A and B and in each of these there is a configCallback which I'd like to be executed as a callback of a dynamic reconfigure server. Both methods use the same parameters and are identical at the moment (I don't know in the future).

class A {   
  ... 
  void configCallback(pkg_name::fileConfig &config, uint32_t level); 
}

class B {   
  ... 
  void configCallback(pkg_name::fileConfig &config, uint32_t level); 
}

In main I create one object per class and I setup both as listener for two distinct topics.

A *a;
B *b;
...
a->createSubscriber("topic_a", 1000);
b->createSubscriber("topic_b", 1000);

I'd like to set a dynamic reconfigure server who calls both the configCallback methods (I'd like to change them simultaneously).

I thought that multiple dynamic servers would work (for example as it is in this post), but the problem is that using separate subordinate namespaces creates two sets of parameters which I don't actually need. I want that one change affects both classes. For clarity, parameters are 2 strings which specify a log file name.

In few words, I'd like that conflict correctly warned by ROS (Tried to advertise a service that is already advertised in this node [/node_name/set_parameters]) should affect my node.

This is what I've done (but namespace conflict happen and changing one parameter through rqt_reconfigure tool affect only one of the classes):

...
dynamic_reconfigure::Server<pkg_name::fileConfig> a_server;
dynamic_reconfigure::Server<pkg_name::fileConfig>::CallbackType f1;
f1 = boost::bind(&A::configCallback, a, _1, _2);
a_server.setCallback(f1);

dynamic_reconfigure::Server<pkg_name::fileConfig> b_server;
dynamic_reconfigure::Server<pkg_name::fileConfig>::CallbackType f2;
f2 = boost::bind(&B::configCallback, b, _1, _2);
b_server.setCallback(f2);
...

How could I solve this problem?

EDIT: I think that there would be no solution. I've rearranged the code to do something similar.