Switching to cross domain tracking from previous Google Analytics implementation

Question

We have in place a simple implementation of GA and have had for some time, the only additional methods we use are setVar and setSessionTimeout. Is there a way we can switch to a cross-domain tracking configuration of GA (where certain links are wired via the _link method) without losing existing tracking data on client systems?

I've run a lot of tests and the more issues solved, the more issues that come up. In a nutshell:

Pre-implementation, the client has these cookies: __utm(a, b, c, z, v). The first step was to change the code and add the _setAllowLinker and _setAllowHash methods, but this was throwing a TypeError. I found this could be avoided by deleting the __utmv cookie before calling the pageTracker methods, and then calling _setVar again afterward.

The new code in place seems to be working OK without throwing an error:

document.cookie = '__utmv=; expires=Tue, 22 Jun 2010 11:57:00 GMT;'+
  ' path=/; domain=XXXXXXX';
var pageTracker=_gat._getTracker(UA-XXXXXXXX);
pageTracker._setAllowLinker(true);
pageTracker._setAllowHash(false);
pageTracker._setSessionTimeout(XXXXX);
pageTracker._setVar(XXXXX);
pageTracker._trackPageview();

The cookies are now updated to not use a hash value, so their values can now be used cross domain, but the problem is that the values in the __utm cookies have been refreshed with new values which means we're losing user history (and new visits will explode).

For example, __utma:

• Before - XX-HASHVALUE-XX.1379282990.1277294951.1277294951.1277294951.1
• After - 1.26318765.1277294984.1277294984.1277294984.1

If it's not possible to switch to cross-domain GA configuration without losing user history, is there a way to fake it on the link which will click through to the next domain. That is, constructing the link URL from the cookies and replacing all the hashvalue prefixes with a 1?

Thanks!

Answer 1

Unfortunately it seems there is no proper way to do this using the ga.js API. I've gone with this solution:

var pageTracker = _gat._getTracker("UA-123456-7");
if (getCookie('__utma') && getCookie('__utma').substr(0, 2) == '1.') {
    // hash value safely removed, flick GA API switch
    pageTracker._setAllowHash(false);
}
pageTracker._trackPageview();

if (getCookie('__utmc') != '1') {
    // remove hash values from all GA cookies
    eraseCookieHash();
}

In the eraseCookieHash function, each cookie is updated manually to replace the hash value with a 1, using the guide at http://code.google.com/apis/analytics/docs/concepts/gaConceptsCookies.html to determine the expires value.