Looking for ideas....

We have similar functionality is a system I support. We spin of the export as a separate request to run in the background then user has the option of waiting at a status screen that monitors the export and reports percent complete or they can opt to be notified via email when the export is done. The email is sent by the export process when complete so no constant pinging of the system.

I am also thinking along the lines of scheduled tasks - in combination with a session check. The pseudocode follows:

1) On ColdFusion page where export functionality is triggered:

<!--- Verify in the database whether the export has been generated. --->
<cfif resultOfVerification is true>
     <!--- Notify user that download ready, then abort. --->
</cfif>

<cfset session.isExportHavingUniqueIDGenerated = false>

<cfif not session.isExportHavingUniqueIDGenerated >
	<cfschedule action = "update"
		task = "checkExport"
		operation = "HTTPRequest"
		url = "http://127.0.0.1:8500/exports/checkExport.cfm"
		startDate = "3/20/2020"
		startTime = "9:00 AM"
		interval = "120"><!--- Task scheduled every 2 minutes --->
</cfif>

2) In the page checkExport.cfm

<!--- Verify in the database whether the export has been generated. --->

<cfif resultOfVerification is true>
	<cfset session.isExportHavingUniqueIDGenerated = true>
	<cfschedule action = "delete"
		task = "checkExport">
</cfif> 

I hear the word "elegance" a lot when people talk about code, and I'm not really entirely sure what it means. I mean, I know what people think they mean, but I'm not sure it lines up with what they really mean. And I've heard a lot of weird advice given in the name of elegance, when said advice might degrade performance or functionality. So, my first piece of advice is not to worry too much about elegance.

OK, that said, this is a perfect job for CFTHREAD and some sort of tracking variables, like the Session scope. You could use CFTHREAD to launch the task, then have it write to a Session variable when done, then the next page request from that user could see the Session variable and respond accordingly. The JavaScript XmlHttpRequest could invoke this page without navigating the user to it directly, of course. This is simpler than a scheduled task, and should be less overhead. Of course, if you're not using Session variables, then you could have the CFTHREAD task write to a database table and have a check of that table on subsequent page requests. But this is a perfect job for Session variables if you can use them.

Dave Watts, Eidolon LLC