Computers are finicky. As stable and reliable as we would like to believe they have become, the average server can cease to function for hundreds of different reasons. Some of the common problems that cause websites or services to crash can’t really be avoided. If you suddenly find your site suffering from a DDOS attack or a hardware failure, all you can do is react to the situation.
 
But there are many simple things that are totally preventable that can be addressed proactively to ensure optimal uptime. To keep an eye on the more preventable issues, setting up monitoring for your entire stack (both the server as well as the individual applications) is helpful. At Zivtech, we use a tool called Sensu to monitor potential issues on everything we host and run.
 
Sensu is a Ruby project that operates by running small scripts to determine the health of a particular application or server metric. The core project contains a number of such scripts called “checks.” It’s also very easy to write custom checks and they can be written in any language, thus allowing developers to easily monitor new services or applications. Sensu can also be run via a client server model and issue alerts to members of the team when things aren’t behaving properly.

Server checks

As a general place to start, you should set up basic health checks for the server itself. The following list gives you a good set of metrics to keep an eye on and why it is in your best interest to do so.

RAM

What to check

Monitor the RAM usage of the server versus the total amount of RAM on the server.

Potential problem monitored

Running out of RAM indicates that the server is under severe load and application performance will almost certainly be noticeable to end users.

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