i've been following the CFLOCK threads for months and months now. i even
started several. unfortunately, the problem is that there doesn't seem
to be any consensus on what's the end-all, be-all, definitive answer to
the question "do you have to lock reads or just writes?" now i can't
speak for anyone else, however, i can tell you what we found during load
testing and you can do judge for yourself.
recently, we hired Allaire to come in and load test (using
SilkPerformer) one of our main applications, which is incredibly
database intensive and uses a lot of CFMODULES and application variables
(no client or session variables). before the test, the application ran
perfect under normal load. however, as soon as we added simultaneous
load (users requesting the same resources at the same exact time), we
immediately crashed with deadlocks in the database and application
errors. again, runs perfect with all of our customers in production, but
fails immediately under load.
up until this point, our strategy had followed the majority consensus:
lock your writes, but not your reads. however, after 14 hours of
analyzing the problems of the load testing between Allaire and I, we
finally just enabled the auto-locking capabilities in CF Admin to see if
that did anything. (keep in mind, the Allaire rep had warned before
about locking reads) the result after enabling auto-lock? not a single
problem for the remainder of the engagement! that's right... no errors,
no deadlocks, nothing. it functioned under load BEAUTIFULLY with the
auto-lock enabled until we finally got the numbers we wanted and
finished the analysis.
so again, i don't want to argue with anyone about their own strategy.
however, seeing it happen right in front of my eyes has me absolutely
convinced WITHOUT A SHADOW OF A DOUBT that allaire is COMPLETELY correct
when they suggest everyone lock BOTH application writes AND reads. and
to tell you the truth, the performance hit for using the auto-lock seems
to be very minimal (at least on our application) so don't worry too much
about that if you don't want to go back and insert all the read-only
locks.
so that's my two cents. hope it helps. =)
-mike
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