I wonder, has anyone actually done any metrics on this to see if automatic
read locking imposes a penalty (that's the conventional wisdom) and if so,
how much of one?
Hal Helms
== See www.ColdFusionTraining.com for info on "Best Practices with
ColdFusion & Fusebox" training, Jan 22-25 ==
-----Original Message-----
From: Peter Theobald [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, December 20, 2000 11:05 AM
To: CF-Talk
Subject: RE: LOCKING revisited...
You just did read locking by hand. Your code has one place where it accesses
an Application variable, and you properly surrounded it with a lock. If you
were to turn on automatic read locking of Application scope the server would
put a read lock around the expression application.myvariable for you and you
wouldn't have to do the lock manually.
In your example, it wouldn't really matter which way you chose, as it's only
ONE access to an Application variable on the whole page. In my example I
have between 10 and 100 accesses TO DIFFERENT Application variables on the
page, and would have to put that three line locked/access/unlock expression
around each one.
I am suggesting that EVEN IN YOUR EXAMPLE it will take longer for the server
to parse three tags and do a read lock than it would to parse ONE tag and do
a read lock (automatically).
At 10:51 AM 12/20/00 -0500, Evan Lavidor wrote:
>Are you saying that if I do the following:
>
> <cflock scope="application" timeout="30" type="readonly">
> <cfset variables.myvariable = application.myvariable>
> </cflock>
>
>and then later on down the page I do the following:
>
> <cfif variables.myvariable GT 10>
> do something
> </cfif>
>
>then I haven't solved the locking "issue"? I thought that by setting my
>application variables to local variables within a lock, I could now
>reference the local variables with abandon and not have to worry about
>locking any more. Is this not the case?!?
>
>Thanks,
>
>Evan
>
>> -----Original Message-----
>> From: Peter Theobald [mailto:[EMAIL PROTECTED]]
>> Sent: Wednesday, December 20, 2000 10:21 AM
>> To: CF-Talk
>> Subject: RE: LOCKING revisited...
>>
>>
>> No offense, but that is nonsense.
>> My Cold Fusion server is still multi-threaded and
>> multi-processed. It is still handling every incoming request at
>> the same time.
>> The only time it will act "single threaded" is when two requests
>> attempt to read an Application scope variable at the same time.
>> And guess what? That is exactly the same thing that will happen
>> if you DONT use automatic read locking, but properly use <CFLOCK>
>> around your Application variables.
>>
>> Automatic read locking doesn't lock the entire page request,
>> (which would be single threading the entire server). It locks
>> read access around those variables that need it.
>>
>> This is not just an academic issue for me. I have a site running
>> with 10-100 reads from an Application structure on every page. To
>> make the code more readable, I am using automatic read locking
>> for Application scope variables instead of
>> <CFLOCK>#Application.myvar#</CFLOCK> tens or hundreds of times on
>> each page.
>>
>> On a related note, if I have automatic read locking enabled for
>> Application scope and I assign a local Variable to an Application
>> variable, it will essentially make a copy to the pointer. Is CF
>> smart enough then to automatically lock accesses to this local
>> Variables, which is pointing into Application space?
>>
>> < !--- automatic read locking is ON for Application variables --->
>> < cfset myvar = Application.bigvar>
>> < cfoutput> #myvar# </cfoutput> < !--- <<<=== IS THIS
>> AUTOMATICALLY LOCKED?? --->
>>
>> At 02:13 PM 12/19/00 -0700, Richard Kern wrote:
>> >It was expressed before that turning this on via the server will
>> essentially
>> >drop your application to single thread mode, slowing down all
>> responses from
>> >the system. Remember that CF is server side so doing this is
>> like knocking
>> >on the door and opening it for each request and then closing it before
>> >anyone else enters, no matter how many people are queued at the door.
>> >
>> >Richard Kern
>> >
>> >-----Original Message-----
>> >From: Peter Theobald [mailto:[EMAIL PROTECTED]]
>> >Sent: Tuesday, December 19, 2000 1:16 PM
>> >To: CF-Talk
>> >Subject: LOCKING revisited...
>> >
>> >
>> >Ok, given that we all agree:
>> >
>> >** Access to shared variables should *ALWAYS* be locked **
>> >
>> >Then why on Earth shouldn't I just turn on Automatic Read Locking for
>> >Application (and Session et al if I use them) scope and only worry about
>> >write locking in my code?
>> >
>> >Why doesn't everyone do that, with the rare exception of some
>> code that has
>> >unusual locking needs.
>> >
>> >I've heard the argument that automatic read locking is a slight
>> performance
>> >hit. It couldn't be more of a hit than parsing <cflock> </cflock> around
>> >every access and still doing the read lock anyway!
>> >
>> >
>> >
>> >-----------------------------------------------------------------
>> ----------
>> >Peter Theobald, Chief Technology Officer
>> >LiquidStreaming http://www.liquidstreaming.com
>> >[EMAIL PROTECTED]
>> >Phone 1.212.545.1232 x204 Fax 1.212.545.0938
>> >
>> >To put this contact information into your Palm device, click here:
>> >http://www.coola.com/cgi-bin/addinfo.cgi?pid=15803&rid=972879910&type=A
>> >
>>
>
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