When CF 2021 came out just before CF Summit back in November of 2020, I was chomping at the bit to try the new features, including SAML, AWS, and Azure integration from the administrator's configuration. But just after upgrading to 2021, we discovered the date bug, and so needed to revert a site or two back to CF 2018.
I've gotten used to manipulating the cf_scripts and jakarta virtual directories manually in IIS rather than use the website configuration tool that comes with CF. Below are how those directories look in IIS.
But there are shortcomings to the manual approach - namely, the ISAPI filter configuration/addition/removal. It turns out that the ISAPI filter is not as easy to manipulate as virtual directories, with both inherited and local configurations. Here is the 2018 tomcat ISAPI filter configured below:
And here is ColdFusion 2021.
Note that the file path is virtually the same save for the root folder. Nevertheless, if they are not in sync with the virtual directory versions, then you are out of luck. So, enter the web server configuration tool. I didn't find any noticeable differences between the 2018 and 2021 version besides the logo. The 2021 version has a brighter color.
In order to start from scratch, I removed all of the websites from 2021, and then added them back - individually. This step is important because I couldn't find a way to split out the sites otherwise, and you need that to happen in order to remove just one or two sites to add to CF 2018.
Once you remove all of them, and add them back to 2021 except for those you want to run under 2018, verify the virtual directories and ISAPI filters are present, refreshing the screen if necessary. Then close the 2021 configuration tool and open the 2018 tool, adding those sites you want configured in 2018.
Finally, once you verify 2018 sites are running, go back into 2021 config tool if you want to, and remove and then add back all sites together under one config folder. But only if you want to.
Now that we have both versions of CF running in dev, we can take our time with the upgrade of each of our websites.
A Couple of Gotchas
Though I wish I could say that the process went as smoothly as that, there were a couple of issues you may also encounter. First, you will likely need to run the WS Config tool as an administrator. Otherwise, it may not have permissions to make the necessary file changes. Second, the applicationHost.config file in the c:\windows\system32\inetsrv\Config ended up with some stray settings, probably associated with my manual attempts to add local ISAPI filters to adjust the version of Tomcat that was running, either the /2018 or /2021 folder version.
As always, I hope this post helps.