As the web gets more complex, with JavaScript framework and library front ends on websites, progressive web apps, single-page apps, JSON-LD, and so on, we're increasingly seeing an ever-greater surface area for things to go wrong. When all you've got is HTML and CSS and links, there's only so much you can mess up. However, in today's world of dynamically generated websites with universal JS interfaces, there's a lot of room for errors to creep in.

The second problem we face with much of this is that it's hard to know when something's gone wrong, or when Google's changed how they're handling something. This is only compounded when you account for situations like site migrations or redesigns, where you might suddenly archive a lot of old content, or re-map a URL structure. How do we address these challenges then?

The old way

Historically, the way you'd analyze things like this is through looking at your log files using Excel or, if you're hardcore, Log Parser. Those are great, but they require you to know you've got an issue, or that you're looking and happen to grab a section of logs that have the issues you need to address in them. Not impossible, and we've written about doing this fairly extensively both in our blog and our log file analysis guide.

The problem with this, though, is fairly obvious. It requires that you look, rather than making you aware that there's something to look for. With that in mind, I thought I'd spend some time investigating whether there's something that could be done to make the whole process take less time and act as an early warning system.

A helping hand

The first thing we need to do is to set our server to send log files somewhere. My standard solution to this has become using log rotation. Depending on your server, you'll use different methods to achieve this, but on Nginx it looks like this:

# time_iso8601 looks like this: 2016-08-10T14:53:00+01:00 
if ($time_iso8601 ~ "^(\d{4})-(\d{2})-(\d{2})") { 
        set $year $1; 
        set $month $2; 
        set $day $3; 
} 
<span class="redactor-invisible-space">
</span>access_log /var/log/nginx/$year-$month-$day-access.log;

This allows you to view logs for any specific date or set of dates by simply pulling the data from files relating to that period. Having set up log rotation, we can then set up a script, which we'll run at midnight using Cron, to pull the log file that relates to yesterday's data and analyze it. Should you want to, you can look several times a day, or once a week, or at whatever interval best suits your level of data volume.

The next question is: What would we want to look for? Well, once we've got the logs for the day, this is what I get my system to report on:

Outputting data

Depending on what the importance is of any particular section, you can then set the data up to be logged in a couple of ways. Firstly, large amounts of 40* and 50* status codes or bad actor requests would be worth triggering an email for. This can let you know in a hurry if something's happening which potentially indicates a large issue. You can then get on top of whatever that may be and resolve it as a matter of priority.

The data as a whole can also be set up to be reported on via a dashboard. If you don't have that much data in your logs on a daily basis, you may simply want to query the files at runtime and generate the report fresh each time you view it. On the other hand, sites with a lot of traffic and thus larger log files may want to cache the output of each day to a separate file, so the data doesn't have to be computed. Obviously the type of approach you use to do that depends a lot on the scale you'll be operating at and how powerful your server hardware is.

Conclusion

Thanks to server logs and basic scripting, there's no reason you should ever have a situation where something's amiss on your site and you don't know about it. Proactive notifications of technical issues is a necessary thing in a world where Google crawls at an ever-faster rate, meaning that they could start pulling your rankings down thanks to site downtime or errors within a matter of hours.

Set up proper monitoring and make sure you're not caught short!