On Monday 01:33 PM 8/18/2008, Tom Jackson wrote:
It's not be a data corruption issue
because you are choosing to overwrite the old data with new data using
the exact same file name. If the data is important, don't overwrite it,
thus no corruption.
No, you've misunderstood the scenario. The file name needn't be the same
to trigger this issue, and the "corruption" doesn't come from serving data
out of a file that's changing, but rather because fastpath caching
mistakenly identifies a new file as being identical to a previously-cached
file (for the reasons I outlined) and erroneously serves the
previously-cached data to the user.
This is a design limitation and arguably a bug in the fastpath caching
implementation, which is potentially quite serious since it silently
serves the wrong data to the user. If you want a more straightforward
(albeit contrived) demonstration of the problem, here you go:
set file [open "/var/tmp/myfile" "w"]
puts $file "ABC123"
close $file
ns_returnfile 200 text/plain "/var/tmp/myfile"
ns_unlink -nocomplain "/var/tmp/myfile"
set file [open "/var/tmp/myotherfile" "w"]
puts $file "XYZ987"
close $file
ns_returnfile 200 text/plain "/var/tmp/myotherfile"
ns_unlink -nocomplain "/var/tmp/myotherfile"
Assuming that /var/tmp/myfile and /var/tmp/myotherfile are created within
the same second, the fastpath caching algorithm will misidentify them as
the same file, and ns_returnfile will therefore erroneously return the
(previously cached) contents of /var/tmp/myfile when it should be
returning the (uncached) contents of /var/tmp/myotherfile.
- John
--
AOLserver - http://www.aolserver.com/
To Remove yourself from this list, simply send an email to <[EMAIL PROTECTED]>
with the
body of "SIGNOFF AOLSERVER" in the email message. You can leave the Subject:
field of your email blank.
