On the SitePoint PHP blog there's a new tutorial from Daniel Berman showing you how to use the ELK stack to monitor WordPress applications, a combination of Elastic Search, Logstash and Kibana. You can find out about setting this stack up in this previous tutorial.
When something does go wrong, one of the first things you’re going to want to look at are the log files. Not because you enjoy it — log files are not easy to decipher — but because they contain valuable information that can shed light on what exactly occurred.
While [you can use the WP Log Viewer], analyzing WordPress and PHP logs is simply not enough. There are also web server and database logs to sift through. To successfully query huge volumes of log messages coming in from various sources and identify correlations, a more solid solution is required.
Enter the ELK Stack.
He shows how to enable the logging features in your WordPress application (in the
wp-config file) and ensure they're not output to the users of your site. He then shows you how to install Filebeat to ship the logs over to the ELK stack. He switches over to the ELK side and shows the configuration needed on Logstash to properly handle the WordPress log format. The remainder of the post helps you get started analyzing the log results and limit it down to only what you need via the Kibana query syntax.