Is the purpose of the online stack just to hold the value of the
custom property? If so, why not use a database such as MySQL or
PostgreSQL? These are carefully engineered to prevent collisions by
multiple users.
George
On Jul 20, 2009, at 7:59 PM, Phil Davis wrote:
I'm looking for the best way to detect data corruption ASAP after it
happens in a custom property of a stack. The stack resides on a file
server and is read & written by many clients. File locking during
reads and writes is already in place and seems to be doing its job,
but occasionally we still have data corruption that creeps in.
Specifically, I want to make a way for the "Client B" app to know that
the value it gets from the "uData" custom property of stack "myStack"
is exactly what the "Client A" app put there a moment before.
Here's how I see this working:
* Client A
o (stack is in memory, file is locked on server)
o sets the uData of stack "myStack" to new value
o puts md5digest of updated uData into "dataDigest" file on
server
o saves "myStack" stack
o deletes stack from memory
o unlocks file on server
* Client B (a moment later)
o locks "myStack" file on server
o puts "dataDigest" file from server into tOldDigest
o goes to stack "myStack"
o puts md5digest of uData custom prop into tNewDigest
o if tNewDigest = tOldDigest, all is well; otherwise
corruption exists
Does anyone see a problem with this approach? Is there a better way to
accomplish the goal? If each client could check the data after its own
write without having to read the stack into memory again to do so,
that would be great - I just didn't see a way for that to happen.
Thanks everyone -
--
Phil Davis
PDS Labs
Professional Software Development
http://pdslabs.net
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