On Wed, Dec 1, 2010 at 11:58 PM, Josh Faust wrote: > The semantics are the same as for any threaded use of a callback queue. >  What that means exactly depends on the callback you're talking about, so, > for example, subscription callbacks on a single topic will not happen in > multiple threads at once unless it's enabled in SubscribeOptions. OK, thanks. I thought it might be something unique to nodelets. I now believe it was num_subscriber_threads I was trying to figure out. --  joq