More than six years ago I created the first version of my DNN Performance Best Practices guide. This guide has been downloaded by thousands of people looking to get the best performance out of their DNN installations. The guide has been the training tool I've used for new members of my staff, and it serves as the baseline for any new DNN installation that we work with. However, in this post, I want to draw attention to what has recently become a silent killer with regard to DNN performance.
Over the course of the last 3 months, we have worked with a number of customers reporting "Random" performance issues, and even site outages. These issues have often been manifested without any real "frequency" or with anything specific that we could track. In each of the cases, we have "re-audited" the installations to validate that nothing new had been installed, or that no changes were made by the customer that might have a negative impact. I dislike "phantom" issues, or things that don't add up, so I started to track things down.
In the end, we found one similarity, each of the sites with "sporadic" performance issues occurred had the "Search: Site Crawler" scheduled job set with a frequency of "1 Minute" and a retry frequency of "30 Seconds." The kicker? This included IowaComputerGurus.com.
Upon further review, we have found that various sites, from DNN 7.3.0 and later, new install or upgrade could have these values set to every 1 minute. I'm not sure what the default value is with new installs as I'm seeing differing results. And one could argue that every 1 minute SHOULDN'T cause issues. However, if an index error does happen the combination of 1-minute interval and 30-second retry make for a site that goes down.
I would recommend that everyone follow the standard practices that are outlined in our guide. Review your site on a regular basis, and ask yourself, based on your site structure, if the timings for the particular scheduled jobs make sense.
If you have a site with random performance issues, that seem to resolve themselves. Check your scheduled job history & detail, you might find something interesting.