How do I take a .NET site down for maintenance?

Question

I have an ASP.NET site that I'm going to have to take down to make some major structural updates to, and I was wondering how I should go about it from the client-side perspective. I have heard of an App_Offline.htm file or something like that, but I've never really gotten that to successfully work. Does anyone know how to do this?

EDIT

My app is running ASP.NET 4.0, for what it is worth.

Answer 1

The trick for IE is to push over the wire particular count of bytes otherwise IE shows not so friendly 404 error anyway. here is more details: http://weblogs.asp.net/scottgu/archive/2006/04/09/442332.aspx

Answer 2

Rather than messing with the app_offline silliness (among other reasons, you can't continue to see the site internally while performing maintenance), I created an additional "down for maintenance" site in IIS, which is normally stopped. It has the same IP, host headers, etc as the main site, but only has a default.aspx, an images folder and a stylesheet. That file contains the "This site will be down for maintenance until xx:xx PM CST" message.

When I'm ready to perform the update, I stop the main site and start the maintenance site, which then processes any requests it receives and, of course, returns the maintenance message.

When the maintenance is complete, stop the maintenance placeholder site, and restart your main site.

If you're using host headers, you can modify this approach so that the site remains internally accessible over your LAN/WAN while the maintenance site is handling external requests. A simple approach is to remove the host headers for <*>.yourdomain.com from the main site before starting the maintenance site, and ensure that the main site has an additional host header that is internally accessible (added to your local hosts file, for instance). When you start the maintenance site, it'll handle external requests while the primary site will handle requests to the internal-only header.

Alternatively (this seems complex, but saves you the trouble of adding and removing headers), create three sites:

1. Main site: Configured as in normal operation.
2. Maintenance site: Has same IP, host headers, etc as main site, but only contains default "down for maintenance" page and any images, css, etc that are required.
3. Internal test site: Duplicates the configuration of the main site and points to the same folders, but only has host headers,etc for an internal name that is not in the public DNS.

This way, you have only to stop the main site and start the other two in order to funnel external traffic to the "down for maintenance" site, while you can still see and tweak the primary site. This is helpful for that last few minutes of testing/bug fixing that tends to come up during a deployment.

Update

If you don't have access to the server or IIS Manager, you most likely won't be able to use any of that. Assuming that your access is limited to your own folder, your options seem to be either to deploy app_offline.htm to the root of the site (ASP.NET checks for that filename), or to just replace the whole site with a "down for maintenance" app. Perhaps someone else will chime in with alternatives.

Answer 3

If you have a good pre-release testing process and careful release procedures you probably won't be down for long.

In that case dropping a file called App_Offline.htm into your site root works fine. IIS will replace your site with it until you remove it. It's a painless way of making sure nothing's updating while you transition.

Mine just has a header with the site logo and a message that we'll be down for maintenance for up to twenty minutes. That's it. It took me about five minutes to write IIRC.

I would definitely recommend this for short sharp down periods of less than half an hour. Anything longer and you're probably looking at a major system change that warrants an approach like David Lively's.