- see footer for list info -<
It's to dow ith race conditions.
Yes, but...
If your doing <cfset session.a = b>
The value of a or b could change before the above statement has completed,
by some other page that also reads/writes the same session variables.
No. This cannot happen (since CF5), or at least not in a way that is
meaningful or relevant. Java will prevent anything else writing to
session.a whilst there is already a line of code accessing it. And b is a
local variable, so cannot be altered by another thread. And to be honest,
what you describe would not be a problem anyhow. It's exactly what would
happen if two threads hit that line of code in series anyhow.
The story with race conditions is more along these lines:
<cfif not structKeyExists(session, "a")>
<!---do some stuff which you only want to do ONCE per lifespan of
session.a --->
<cfset session.a = "OK, it's been done: this is set so it ain't done
again.">
</cfif>
Now... one thread hits the first line, and the test passes as session.a
doesn't exist. And before the first thread gets to the end of the <cfif />
block, a second thread hits the <cfif>. Again... the variable doesn't
exist, so the SECOND thread also starts executing the inner block.
THAT'S a race.
One might say "well that's just dumb having the check variable set at the
bottom of the <cfif /> block anyhow. This is true, but even if it was the
very first line in the <cfif /> block, it's still possible that a second
thread hits the <cfif> before the first thread completes the following
<cfset>.
--
Adam
_______________________________________________
For details on ALL mailing lists and for joining or leaving lists, go to
http://list.cfdeveloper.co.uk/mailman/listinfo
--
CFDeveloper Sponsors:-
- Hosting provided by www.cfmxhosting.co.uk -<
- Forum provided by www.fusetalk.com -<
- DHTML Menus provided by www.APYCOM.com -<
- Lists hosted by www.Gradwell.com -<
- CFdeveloper is run by Russ Michaels, feel free to volunteer your help -<
