Note: This blog post is from 2010. Some content may be outdated--though not necessarily. Same with links and subsequent comments from myself or others. Corrections are welcome, in the comments. And I may revise the content as necessary.
How often have you seen (or seen others complain of getting) a CF page running longer than it's "supposed to" by a timeout you have set
. Maybe you've set the CF Admin "request timeout" (first setting on first page of the Admin), or used the cfsetting requesttimeout tag or the timeout attribute on some specific tag if it's available, trying to get the request to "end" in 60 seconds, and yet you see a request running for 3 minutes, 3 hours, or 3 days! How can that happen?
Or same with if you've set the request to timeout using an alerting feature in a CF monitor like CF Enterprise server monitor, FusionReactor, or SeeFusion.
And perhaps you've seen this error from ColdFusion, in your logs or on-screen:
The request has exceeded the allowable time limit Tag: cfoutput
Do you know what this means? It's usually not what you think, and it may appear as I said 3 hours after a request was "supposed to timeout" in 60 seconds. I've even seen experienced CF developers who get thrown by this challenge. It's not new (and for those reading this even in the CF2016 era, it still happens). And it's not so much a "bug" (in either CF or the monitor tools) but just a situation that you need to understand, and there can be some ways to resolve things.
In this entry I'll try to help explain this surprisingly common problem and I hope to correct some equally common misconceptions. I'll even contend that the info in this error message is often useless and indeed misleading (and therefore the feature producing it ought not be relied upon completely, and should perhaps even be turned off for many). More important, again, there may be a way to "really" kill such a long-running request. Along the way, I'll share some things that I've not seen documented elsewhere.
I also share a solution that may work for query processing but it's NOT about a tag attribute but rather a CF Admin setting in the datasource "advanced settings" to set a "query timeout". This was added in CF 9, but many never noticed. If that's your problem and you want to skip to more on that here, feel free. but you may want to come back and read the rest as it is STILL not a perfect solution.
Strap on your seatbelts. We're going for a bit of a ride (if this situation was easy to understood in the length of a tweet, then perhaps everyone would already understand it and not find it challenging!) As always, I welcome feedback.