Steve:
I'm beginning to suspect we don't need to use the duplicate() function in
the specific case of a CFSETing a query, for example:
<cfset request.app.MyQuery = application.requestapp.MyQuery>
but the duplicate() function is required in the case of "complex data types
like structures" (Allaire's words) and I don't know what else.
If my suspicion is correct it enables at least part of your original intent
that is, no locks needed where request.app.MyQuery is used in the app.
best, paul
At 11:21 AM 8/28/00 -0400, you wrote:
>I think we only need to use the duplicate() function when we set the
>request variable, not when we set the application variable. i.e.
>
>use it here:
><cfset request.app=duplicate(application.requestapp)>
>
>no need to use the duplicate() function here:
><cfset application.requestapp=request.app>
>
>
>is that right?
>
>Steve
>
>
>BOROVOY Noam wrote:
> >
> > Thought we bashed this one out a while back:
> > The "pointers" or "references" might be stored in thread safe memory (like
> > the request scope) but the memory they point to (or reference) is NOT
> thread
> > safe.
> >
> > Here's my current approach to tackle this problem (based on the accumulated
> > tips from the list):
> > In App_globals
> > 1. set simple globals into the request scope - no locking issues - tiny
> > performance hit on setting all the values for each request probably
> equal or
> > less than the hit of locking.
> >
> > 2. set structures / arrays into the application scope - first check if
> > already defined and loaded - do a full check using IsDefined followed by
> > isArray / IsStruct and a check for minimum size - just in case there was a
> > DB error on the previous load.
> > Then if not defined Write lock and load the data from the DB - i.e. define
> > the data element, include the needed query and fill it up.
> > If defined do nothing it's already there for you to use.
> >
> > 3. In Index.cfm wrap the whole file after the include of app_locals with a
> > read lock. (if you reference any application vars in app_locals you will
> > want to lock that as well after the include of app_globals.
> >
> > The read locks will not hit performance - they will only affect performance
> > on the first hits after a reboot and once the application variables
> time out
> > and need to be re-loaded - which should hardly happen on a busy site.
> >
> > So Steve - only two locks for the whole application - just placed in
> > different locations ;-)
> >
> > For session vars things get messier as you want to write to them deep down
> > in the application - but I found that a well designed app can usually avoid
> > the need for session variables and if really needed use client vars or do
> > the locking everywhere...
> >
> > HTH,
> > Noam
> >
> > ----------
> > From: Fred T. Sanders [SMTP:[EMAIL PROTECTED]]
> > Sent: Monday, 28 August 2000 16:30
> > To: [EMAIL PROTECTED]
> > Subject: Re: No more need for cflock!!
> >
> > Yes it does only set a pointer, I've tested that before and
> found it
> > to be
> > the case.
> > However (and I haven't tested this) the request scope by its very
> > definition
> > in CF
> > is supposed to be thread safe. Wouldn't this in effect be
> treated by
> > the
> > CFAS as read locked
> > pointer?
> >
> > Fred
> >
> > ----- Original Message -----
> > From: "Scott Talsma" <[EMAIL PROTECTED]>
> > To: <[EMAIL PROTECTED]>
> > Sent: Monday, August 28, 2000 9:42 AM
> > Subject: RE: No more need for cflock!!
> >
> > > I too believe that
> > >
> > > <cfset request.app = application.requestapp>
> > >
> > > only sets a pointer. My question regards when do we need to set
> > read
> > locks?
> > >
> > > When all application data resides in the database, and we
> > establish that
> > > application variables will only take on these values (and that no
> > other
> > > application variables will exists), then doesn't there exist an
> > implicit
> > > guarantee that (outside of Steve's code) only reads from the
> > request
> > > variable (a pointer to the application variables) will take
> place?
> > Is
> > there
> > > any danger when two threads simultanously read from the same
> > memory
> > address?
> > >
> > > -----Original Message-----
> > > From: Cameron Childress [mailto:[EMAIL PROTECTED]]
> > > Sent: Montag, 28. August 2000 15:33
> > > To: [EMAIL PROTECTED]
> > > Subject: RE: No more need for cflock!!
> > >
> > >
> > > Steve... We've been using this technique for some time now. I
> > see that
> > you
> > > are traveling down same path now, so here are comments on what
> > I've found
> > by
> > > doing this so far...
> > >
> > > One mistake I made early on was code similar to this line from
> > your code
> > > below:
> > >
> > > <cfset request.app=application.requestapp>
> > >
> > > I believe that this actually only creates a pointer to your
> > application
> > > struct, so when you call something in 'request.app', it's still
> > technically
> > > accessing data in your application scope, and could still lead to
> > memory
> > > issues without a lock. You can solve the problem by doing this
> > instead:
> > >
> > > <cfset request.app= Duplicate(application.requestapp)>
> > >
> > > Also, I am very concerned about the effect of this method on a
> > site which
> > > stores a large amount of data in the application scope. You're
> > basically
> > > making CF copy the entire scope on every page call. This could
> > cause
> > > enormous performance problems on a large, heavy traffic site with
> > alot of
> > > data kept in memory.
> > >
> > > I've done some rudimentary load testing with this technique, and
> > haven't
> > yet
> > > seen a serious issue with decreased performance, but as I've been
> > adding
> > > more and more data into the application scope for a current
> > project I've
> > > become more and more worried that the same test would yield
> > different
> > > results a second time.
> > >
> > > I probably will hold off on the load testing for a bit longer
> till
> > I get
> > > finished stuffing everything I need to into the application
> scope,
> > but
> > does
> > > anyone else have any comments for or against this?
> > >
> > > -Cameron
> > >
> > > --------------------
> > > Cameron Childress
> > > McRae Communications
> > > p. 770-460-7277 x.232
> > > f. 770-460-0963
> > >
> > > > -----Original Message-----
> > > > From: Steve Nelson [mailto:[EMAIL PROTECTED]]
> > > > Sent: Saturday, August 26, 2000 10:34 AM
> > > > To: Fusebox
> > > > Subject: No more need for cflock!!
> > > >
> > > >
> > > > I've just hit upon a technique that would mean we only ever
> need
> > to use
> > > > cflock two times in a fusebox home application. This is for
> > application
> > > > variables, session and server variables would need to do the
> > same too i
> > > > imagine (personally i never use them)
> > > >
> > > > First I want to propose a new filename, qry_globals.cfm the
> > point of the
> > > > file is to store application wide queries, it would sit in the
> > root
> > > > directory of your home application. It would run queries from
> > the
> > > > database upon booting up the server then store the variables
> > into
> > > > memory. This massively reduces stress on the database,
> > generally it's
> > > > an excellent technique. The problem has been with cflock.
> > people
> > > > forget to use it and CF WILL blow up on you if you forget
> to use
> > > > CFLOCK. So I figured out a way to bypass all the cflock
> > nonsense and
> > > > only require two cflocks in your entire application, which do
> > very small
> > > > tasks.
> > > >
> > > > Check this code out. It's wicked cool (Hal let me know how I
> > did on my
> > > > fusedocs, i'm just starting to get into them, and love 'em! :)
> > > >
> > > > <cfsetting enablecfoutputonly="yes">
> > > > <!--- qry_globals.cfm --->
> > > > <!---
> > > > || I start by doing a check to see if the variable
> > > > application.requestapp exists if this
> > > > || variable exists then I set
> request.app=application.requestapp
> > and I
> > > > do not rerun any
> > > > || application wide queries. If this variable does not exist I
> > rerun
> > > > all the queries
> > > > || and set application.requestapp=request.app
> > > > ||
> > > > || Then anytime I want one of these values I call it as:
> > > > request.app.queryname instead
> > > > || of application.queryname. By doing this I no longer need to
> > use
> > > > cflock in anywhere
> > > > || other than this file.
> > > >
> > > > || [EMAIL PROTECTED]
> > > >
> > > > ||
> > > > -->
> > > > <-- request.app - this is a copy of an application variable
> > called
> > > > application.requestapp
> > > > ++> application.requestapp - this is where all application wide
> > queries
> > > > sit
> > > > +++
> > > > --->
> > > > <cfset request.maindsn="valuemusiclocal">
> > > > <cfapplication name="blbl"
> > > > applicationtimeout="#createtimespan(0,1,0,0)#">
> > > > <cflock name="#application.applicationname#" timeout="60"
> > > > type="readonly">
> > > > <cfif isdefined("application.requestapp")>
> > > > <cfset request.app=application.requestapp>
> > > > <cfset runrequest="no">
> > > > <cfelse>
> > > > <cfset runrequest="yes">
> > > > </cfif>
> > > > </cflock>
> > > > <cfif runrequest>
> > > > <cfset request.app=structnew()>
> > > > <cfquery name="request.app.getstates"
> > > > datasource="#request.maindsn#">
> > > > select * from states
> > > > where active=1
> > > > order by state_name
> > > > </cfquery>
> > > > <cfset request.app.state_rows=structnew()>
> > > > <cfloop query="request.app.getstates">
> > > > <cfset request.app.state_rows[state_id]=currentrow>
> > > > </cfloop>
> > > > <cflock name="#application.applicationname#" timeout="60"
> > > > type="exclusive">
> > > > <cfset application.requestapp=request.app>
> > > > </cflock>
> > > > </cfif>
> > > > <cfsetting enablecfoutputonly="no">
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > <!--- dsp_address.cfm --->
> > > > <!---
> > > > || I'm demonstrating the use of a request.app variable, note
> > that
> > > > || I do not need cflock, and I do not need to rerun the
> > getstates query
> > > >
> > > > || [EMAIL PROTECTED]
> > > >
> > > > ||
> > > > -->
> > > > <--
> > > > ++> request.app.getstates - this is a query with all the states
> > in it
> > > > +++
> > > > --->
> > > > <select name="state_id">
> > > > <cfoutput query="request.app.getstates">
> > > > <option value="#state_id#">#state_name#
> > > > </cfoutput>
> > > > </select>
> > > >
> > > >
> > > > Now that's a beautiful thing! eh?
> > > >
> > > > Steve
> > > >
> > ------------------------------------------------------------------
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