Cache profile for WCM internet site

Hmmm… this took me a while to understand… but the solution is rather simple.

I wanted to activate cache profile for my customer WCM site, so that only anonymous users will see a shared cached version of the page.

Naturally – all anonymous users see the same version of the page and do not have editing rights nor can they see draft versions – so typically all you need to do is:
1: Go to site actions à site settings àsite collection administration à site collection output cache
2: Set the anonymous cache profile to “public internet (purely anonymous)
3: Click OK

And you are done.

But – I noticed there were no improvement in system-load (FE and DB servers) per requests and overall performance did not improve.

I went back to site collection output cache settings page and selected the “Enable debug cache information on pages” checkbox. Enabling this will append to the HTML a debug message stating when the current page was rendered and if cache was in use.

To my surprise (or not) I found this message:
"8 Output cache not used. Reason: User can view an unpublished version of the current page."

This meant that caching was not activated for anonymous users because they had access for unpublished version of current page? Not!

After contacting the WCM team, I got an interesting reply from Kai Lee (Thanks!) saying that this message will come up if the current user (anonymous in my case) have editing access or can view draft versions ANYWHERE IN THE SITE COLLECTION!

Well, I still have to check where anonymous users have this access in my site collection (worrying…) but there is (thank god!) a nice workaround.

Going into the “public internet” cache profile allows you to set "Allow Writers to view cached content" to “true”.

This is important to understand: for authenticated users, who can edit pages and suppose to view draft versions – this is BAD. But for my scenario – where I have no interest of allowing anonymous users to view these contents anyhow – it is a good workaround and what do you know?
It solved the problem!!!

So thanks Kai Lee again,

Hope this will save some time to the rest of you…

Thanks, Shai Petel.