code that calls callbacks. But it is well worth it to avoid queuing
callbacks, and the improved P99 times as a result.
+### DestructorCheck
+
+Often for an object requesting callbacks from other components (timer,
+socket connect, etc.) there is a chance that the requestor will be
+deallocated before it'll receive the callback. One of the ways to avoid
+dereferencing the deallocated object from callbacks is to derive the
+object from DelayedDestruction, and add a delayed destruction guard
+to the callback context. In case if keeping the object around until
+all the requested callbacks fire is too expensive, or if the callback
+requestor can't have private destructor (it's allocated on the stack,
+or as a member of a larger object), DestructorCheck can be used.
+DestructorCheck is not affecting object life time. It helps other
+component to detect safely that the tracked object was deallocated.
+
+The object requesting the callback must be derived from DestructorCheck.
+The callback context should contain an instance of
+DestructorCheck::Safety object initialized with a reference to the
+object requesting the callback. Safety object can be captured by value
+in the callback lambda, or explicitly added to a predefined callback
+context class. Multiple instances of Safety object can be instantiated
+for the same tracked object. Once the callback is invoked, before
+dereferencing the requester object, callback code should make sure that
+`destroyed()` method for the corresponding Safety object returns false.
+
### EventBaseManager
DANGEROUS.