Domain-based caching.

I have three separate domains. Each one is pointing to one single-context MODx installation. The difference between domains is conditional and based on If extra snippet that checks the site_url changes. Because of this, page load time is extremely slow. About 3 seconds. I discovered really nice Supercache extension, that increases page load in couple times. But problem is, when I visit first domain it caches and on second domain I am seeing content from the first one. Can I somehow clear the cache when site_url is changing?

I was trying to make $modx->cacheManager->refresh(); according to server HTTP_HOST, but no luck. It refreshes cache every single time domain is shown. E.g on every page visit on exact domain, so performance stays the same bad.

The problem was solved by using Domaineer plugin by Mark-H. Instructions is here: https://github.com/Mark-H/Domaineer. Just array of domain-based options and that's all! No modifiers was used. Performance is great, by the way. Its a bit tricky sometimes. For example, when you need to hide specific resource in menu from specific domain. I just created +hideMenuItem option with "&excludeDocs=`55`" value and placed [[!+hideMenuItem]] in wayfinder call.

Tip: Documentation says that plugin must run on WebPageInit event, but I noticed a little performance boost by setting it to OnHandleRequest.