Lee Kelleher

Putting your ASP.NET Web Application in Maintenance Mode (using ISAPI_Rewrite)

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Prompted by @slace’s tweet:

I replied with a suggestion that we’ve used in the past. Aaron said I should blog about it… so here I am (again)!

A while ago we needed to do an Umbraco upgrade (from v3 to v4) on a production server – in my opinion it was a pretty major upgrade on a live site, we had done a couple of test upgrades on dev and staging, all was successful.  But since there was various parts of the site that we need to regression test, I felt it best to take the entire site offline whilst we upgraded.

Usually creating an “App_Offline.htm” page in the root of your web app is enough to take it offline.  However that was no good for testing… so what to do?

This is where ISAPI_Rewrite is your best friend, (or .htaccess to be precise).  We needed to configure the site to allow access for us and redirect everyone else to a “Site under maintenance” page.  I found a few examples across the web, but to save you all that hassle, here are the .htaccess rules that we use:

# BEGIN Maintanence Mode
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} !/offline.html$
RewriteCond %{REMOTE_ADDR} !^$
RewriteRule ^(.*)$ /offline.html [R=302,L]
# END Maintanence Mode

What does it do? The first “RewriteCond” rule checks that you are not requesting the “offline.html” page (otherwise you would end up in a constant loop!) The second “RewriteCond” checks the IP address of the visitor – in my case it was “” (remember to escape the dots). If those two rules aren’t satisfied, then the “RewriteRule” is used, redirecting the visitor to the “offline.html” page.

As always, I am open to any suggestions or improvements!