Rewrite Maps in IIS Make web.config Too Large - iis-7

Question

I am migrating a website which is/will be running on IIS and I will be using rewrite maps to 301 redirect old ".asp" URLs to a new style of URL. For many thousands of URLs there is no pattern, so it appears I must rely on rewrite maps.
My problem is that the default web.config size limit is 250kb, and in my environment, I don't have access to change this (as can be done at the registry level - if one had access).
I have looked into moving the rewriteMaps section to an external file, but the external files also have the default size limit of 250kg, so this is also not going to work.
I am looking for some other way to handle this... I am sitting at 242kb currently and have over twice the amount of old to new redirect mapping to add.
Thanks in advance.

Answer 1

As I am in a shared environment, there was no solution other than to move it to a single external config file, which was again, limited to 250KB.
So here is what I did:
I filled up the map to capicity with the highest-trafficked redirects and of course any groups of urls that could be redirected using a pattern (so they would be fastest).
For the 100k remaining long-tail of the redirects, I put them into a REDIRECTS table in the db... SO, after the request passes all of the rewrite rules in the file (and of course, doesn't hit any), it defaults the request to a certain script. One of the first things the script does is check the REDIRECTS table, and if an entry exists, I do a redirect in the code... it's slower, but most of the stuff in the table is long tail, and as I said, the most visited redirects are still in the file. This has worked well for me so far, and I can add as many redirects as I want... e.g. if a page title/url gets edited, my admin area automatically adds the redirect, etc.

Answer 2

The Nativerd.dll file uses the value of this registry key to determine the maximum allowed size, in KB, of the Web.config files. The Configuration system assumes a default value of 250 KB in Windows Server 2008 and 100 KB in the release version of Windows Vista.
The reason for the 250KB limit is to reduce attacks for uploading a large web.config file. You can change the the limit by altering the upper value in your registry:
HKLM\SOFTWARE\Wow6432Node\Microsoft\InetStp\Configuration\MaxWebConfigFileSizeInKB (REG_DWORD)
See: Description of the registry keys that are used by IIS 7.0, IIS 7.5, and IIS 8.0
Another option is to split your web.config files into multiple smaller files.

Answer 3

We were stuck on this for a long while, we ended up writing our own 301 redirector. In sitecore it was in a pipeline patched after ItemResolver which consumes the large file (not included in any Web.configs). We could not use the "registry hack" option as it an Azure Service App and there is no (easy and cheap) access to the registry.

Answer 4

You can split up your configuration into a few different files as Neill said.
You will have a main web.config file in which you’ll reference sub config files by adding a configSource attribute onto the sections you would like to split into other files.
For example, if you’d like to split the section “appsettings” in another file, you would change the appSettings section in your web.config file to :
<appSettings configSource="appsettings.config" />
and in the appsettings.config file, you would add all your appsettings entries like they were in the original web.config file, for example;
<appSettings>
<add key="aspnet:RestrictXmlControls" value="true" />
<add key="FeedCacheTime" value="300" />
<add key="FeedPageUrl" value="/_layouts/15/feed.aspx?" />
<add key="FeedXsl1" value="/Style Library/Xsl Style Sheets/Rss.xsl" />
<add key="aspnet:AllowAnonymousImpersonation" value="true" />
</appSettings>
Obviously with the rewrite maps instead.