Customer received wrong transaction number

Question

Hi all,
I encountered a strange problem with our shopping cart today.  We had two transactions that occured around the same time.  Let's say, customer A was assigned transaction number 100 and customer B transaction number 101.  Both transactions were saved into the database correctly.  However, customer B received an email confirmation stating that his transaction number is 100.  The details of his transaction in the email are correct, only the transaction number is mixed up.
Here's roughly the code:
// get transaction number
transNum = salesCFC.createTransactionNumber()
// save shopping cart into db
salesCFC.saveTransaction( transNum, session.shoppingBagObj)
// email customer
<cfmail from="" to="" subject="Transaction Number #transNum#">
     // shopping bag printout
</cfmail>
transNum is a local-scoped variable.
I have been scratching my head to understand how this happened.  We only discovered this issue because customer B wanted to cancel his transaction and he gave the transaction number belonging to customer A.  We checked our sent mail folder and sure enough both customers received confirmation emails with the same transaction number.
Is it possible that customer B's transNum variable got corrupted and crossed with customer A's transNum?

Answer 1

Here's roughly the code:
Can you post the actual code.  Including the code for createTransactionNumber().  Snip out anything that's not relevant (so code that does not use or influence the transaction number in any way... and excise any mark-up ;-), but include any branching and looping logic, and the relationship between any different files involved, incuding how each is called from other files.
It sounds like the transaction number is correct when you call saveTransaction(), but it gets overwritten between there and the CFMAIL call.  To state what is probably obvious.
Perhaps at some point you are inadvertantly putting the transaction number in some shared-scope variable which is being accessed by reference rather than value, eg one can have two requests doing this:
variables.myStruct = application.myStruct;
Which might look like variables.myStruct is local, but all it is is a reference to the shared scope variable.  So if one then does this:
variables.myStruct.someVariable = "some request-specific value";
Then all requests accessing variables.myStruct.someVariable will be accessing the same variable (the one in the application scope), and that variable will have a request-specific value.  Bad.  This will be the case for any complex objects in CF, except for arrays.  I only mention this because we've quite often been caught out by this.
Adam