We recently added a PageRank alert service to the Sitening SEO Tools. Historically, the published PageRank for web pages in Google’s index was updated quarterly. While it doesn’t change a whole lot, an email or RSS alert is still handy if you’re tracking the SEO for your site. Since we started tracking the PageRank for about 200 urls, we’ve seen quite a lot of shuffling. I’m beginning to think that they’ve moved to continuous updates for published PageRank.
The Google index used to do a thing called the Google Dance, but that was phased out in favor of continuous updates. According to this page the Toolbar PageRank is still an infrequent occurance, but I’m beginning to suspect it’s moving towards continuous updates. Because of more frequent updates, and because the Google data centers update asynchronously, we’re finding it necessary to consult multiple data centers before reporting the PageRank. So you can see for yourself, I’ve added a Survey feature to the PageRank checker. Check the box and see if there are any discrepancies between data centers for your URL.
Today, I’m noticing that there are at least four data centers that seem to be consistently reporting different data: 64.233.163.*, 64.233.183.*, 72.14.203.*, 72.14.223.*.
We’ve also turned off the PageRank caching that we use to limit the number of requests we need to make to Google. I think instead we’ll need to increase the number of requests. The PageRank alerts will need to start polling multiple data centers, and we may need to do something similar with SERP Tracker. We’re looking at the possibility of trying to identify which data centers have the most recent data, then directing all of our requests there.