Barry,
I don't think it is not that simple/obvious -- you store a query for
caching and ONLY reading, then it is not obvious that the
currentrow/loop cursor is written - I actually took for granted that the
cursor would be per request, and was not an integral part of the actual
variable/query.
I would strongly recommend against cflock here, use duplicate.
/H.
--
Hugo Ahlenius
-------------------------------------------------------------
Hugo Ahlenius E-Mail: [EMAIL PROTECTED]
Project Officer Phone: +46 8 412 1427
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-------------------------------------------------------------
| -----Original Message-----
| From: [EMAIL PROTECTED]
| [mailto:[EMAIL PROTECTED] On Behalf Of Barry Beattie
| Sent: Tuesday, March 21, 2006 12:11
| To: [email protected]
| Subject: Re: [CFCDev] application-scoped singletons and thread safety
|
| the biggest issue is usually understanding what's happening.
|
| just because there's a couple of lines of code together with a loop
| only means those instructions are being executed sequentually
| _by_that_thread. In between which, other threads have their "slice of
| the processor" to run instructions and, in this case, access to common
| memory (ie: Application scoped variables).
|
| All shared scopes have this issue to consider and that's why cflock
| (yeah it *is* an ugly way to go) works: deny other threads access to
| this shared scope until the first thread hits the </cflock>. copying
| the data and using the copy for processing avoids the issue.
|
| it's also related to the old
|
| if app var doesn't exist
| lock
| if it still really doesn't exist (not created by another thread
| while locking this thread)
| create app var
| end if
| end lock
| end if
|
|
| it's an easy thing to forget when you're deep in the innards of some
| code.
|
| my 2c
| barry.b
|
|
|
| On 3/21/06, Hugo Ahlenius <[EMAIL PROTECTED]> wrote:
| > I experimented a bit more, and it has nothing to do with
| CFCs really
| > -- in the application scope (and also likely in other
| shared scopes)
| > the currentrow cursor is shared with the queries, at least
| in CFMX 6.1
| > and BD 6.2.1 (which I have tested, don't have access to CFMX 7).
| >
| > Workarounds:
| > * Best is to duplicate (for encapsulation etc)
| > * One can also cflock (ugly!)
| > * Or do an index loop 1 to recordcount
| >
| >
| > --
| > Hugo Ahlenius
| >
| > -------------------------------------------------------------
| > Hugo Ahlenius E-Mail: [EMAIL PROTECTED]
| > Project Officer Phone: +46 8 412 1427
| > UNEP GRID-Arendal Fax: +46 8 723 0348
| > Stockholm Office Mobile: +46 733 467111
| > WWW: http://www.grida.no
| > Skype: callto:fraxxinus
| > -------------------------------------------------------------
| >
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