central controller metrics & request path updates (#2012)

* internal db metrics

* use shared mutexes for read/write locks

* remove this lock. only used for a metric

* more metrics

* remove exploratory metrics

place controller request benchmarks behind ifdef

osdep/BlockingQueue.hpp

@@ -117,7 +117,6 @@ public:
 	}
 
 	inline size_t size() const {
-		std::unique_lock<std::mutex> lock(m);
 		return q.size();
 	}