Hi,
following the different states a session can be in, plus the possible
transitions from one state to another, we will have an issue if we don't
protect the sessions state against concurrent access and modifications.
For instance, as right now, the session's state is a volatile variable
in AbstractIoSession :
protected volatile SessionState state;
it looks like it's protected. It is, only of we consider it from a
read/write pespective. That mean it's safe to read the sate, it's safe
to change it, there is no way we can't do that as an atomic operation.
But there is something we can't do, it's changing the state *and* check
that the transition is ok :
if (state == CONNECTED ) {
state = SECURING
}
for instance, might fail as the session's state may have changed before
we try to change it.
So we need to protect the state transition from concurrent accesses.
Again, one possible solution would be to use a ReentrantReadWrite lock,
to allow fast session's state reads, and safe transition.
I would also suggest that we have only one way to change the state,
throw a method like :
void changeState( SessionState from, SessionState to)
in order to be able to check that the transition does not violate the
table of possible transitions.
wdyt ?
--
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com
