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Predicate http_gc_sessions/1
 http_gc_sessions is det[private]
 http_gc_sessions(+TimeOut) is det[private]
Delete dead sessions. There are two modes. if gc(passive) is active (default), session GC is executed if a new session is created and if the last GC was more than granularity ago. If gc(active) is on, a thread is created that runs the session GC every granularity seconds.

http_gc_sessions/0 is called each time when a session is created.