how to create multiple custom 503 pages in IIS - iis

Question

A Temporary down page (e.g. updating your servers SW) should ideally have a response code of 503, but you could get away with 307, but in no case should it be 200 (as google will index this and it will affect your SEO)
In IIS rewrite rules, you have 3 options for implementing a redirect to a down page, rewrite, redirect and customResponse:
<action type="Rewrite" url="/site1.html" />
<action type="Redirect" url="/site1.html" redirectType="Temporary" />
<action type="CustomResponse" statusCode="503" subStatusCode="0" statusReason="Site Unavailable" statusDescription="Down for maintenance" />
The problem is if you want a 503 response, you cant redirect to the required page.
We have 3 websites for different brands using episerver CMS.
When we do maintenance, or just want to take a site down, we have a single azure web app (aka iis) which has 3 holding pages, one for each.
so our site down website has 3 pages:
/site1.html
/site2.html
/site3.html
We use Azure traffic manager to point to the live site or the site down page, and we currently have redirects which work, but incorrectly give 200 response:
<rewrite>
<rules>
<rule name="site1" stopProcessing="true">
<match url=".*" />
<conditions>
<add input="{HTTP_HOST}" pattern="mysite" />
</conditions>
<action type="Rewrite" url="/site1.html" />
</rule>
<rule name="site2" stopProcessing="true">
<match url=".*" />
<conditions>
<add input="{HTTP_HOST}" pattern="myothersite" />
</conditions>
<action type="Rewrite" url="/site2.html" />
</rule>
etc.
</rules>
</rewrite>
In order to fix this issue (offer a different site down page per site, and respond with 503), what are the options?
I would guess its possible to setup something like 3 different named virtual hosts, each with nothing except a custom 503 error page + a catch all CustomResponse action? Any examples of such a config?
To be clear, our app may well be running normally, but we may want to use our traffic manager to point the public at a "down" page which has a 503 respose during maintenance. The website sorving the down page has nothing to do with the website serving the site/applicaion itself.

Answer 1

Sadly, as the Microsoft document describes – there is no way to customize the 503 HTTP error.
Even use rewrite to make it display custom 503 page, In fact the request get into IIS and rewrite successful, then response to client. The whole process is perfect and your web service doesn’t stop.
The error is detected by the IIS server as it attempts to hand the incoming request to application. Everything application does is performed in its app pool. Modules like rewrite and custom error page are all executed in this way. 503 handled by the http.sys you cannot create a custom error page at all, as it is processed before it gets to iis. Therefore, both hope that the web server will stop reporting 503, but also hope that the server can process the request to display the page you defined. These two conflicts.
If your application is asp.net, there’s another way to custom 503. You can place a text file named "app_offline.htm" in the root of the site, all requests to that website will redirect to that app_offline.htm file. Basically, if you need to take an entire ASP.NET site offline, you can place some nice message in that file. Then, any new requests to a URL, any URL, in that website will redirect to that file allowing you to do maintenance to the site, upgrades, or whatever. It is not really a redirect though. ASP.NET essentially shuts down the site, unloads it from the server, and stops processing any requests to that site. That is, until you delete the app_offline.htm file - then things will continue as normal and your ASP.NET site will load up and start serving requests again.