Charles Hooper

Thoughts and projects from a site reliability engineer

Intro to Operations: Availability Monitoring and Alerting

I’m writing a series of blog posts for managers and other people without an operations background in order to introduce certain best practices regarding Operations. For the rest of the blog posts, please visit the introductory Intro to Operations blog post!

Another area I’ve seen alot of early stage startups lacking in is availability monitoring and alerting. The essence of availability monitoring and alerting is being notified when your service is not working as expected, including when it’s simply down, isn’t meeting formal or informal SLAs (e.g., it’s too slow), or certain functionality is broken.

What I typically see is that some effort was made to set up this type of monitoring before and never maintained. Symptoms include poor monitoring coverage (servers missing from the config, services monitoring nearly non-existent), large amounts of false positives and negatives, inactionable alerts, and alerts that go unignored because of the previous issues.

Symptoms on the business include not knowing when your service is down and finding out that your service is broken from your customers. Finding out that your service is down from your customers is not only embarrassing but it also shakes their confidence in you, affects your reputation, and may even lead to lost revenue.

The good news is that it doesn’t have to be this way. When availability monitoring is set up properly, maintained, and you and your employees agree to approach alerts a specific way, you will be able to reap a variety of benefits. Here’s what I recommend:

  1. First, collaborate with your employees to define who is in the pager rotation and the escalation policies. Ask yourself: What happens when the on call engineer is overwhelmed and needs backup? What happens when the engineer goes on vacation?

  2. Next, take inventory of what services you rely on and define an internal SLA for them. This does not have to be a super formal process, but this inventory and SLA will be helpful for deciding what thresholds to set in your monitoring to avoid false positives. Try to see the big picture and think about everything such as:

    • Servers,
    • Self-managed supporting services like web servers, databases, email services,
    • Application functionality and features - one strategy I like is exposing a “health check” service that can be checked by the monitoring agent,
    • Third party services like remote APIs.

Your inventory and SLA definition is a living document; remember to keep it up to date!

  1. Then set up whatever monitoring package you or your engineers decided to use (self-hosted or third party) such as nagios, Zenoss, Pingdom, or CopperEgg and have your monitoring configured for those services. If you’re really good, you’ll check your configuration into its own source control repository. If you go the self-hosted route, it may also be worth having your monitoring server monitored externally. Who’s watching the watcher indeed.
  1. Think about integrating your monitoring with a pager service such as PagerDuty. Services like PagerDuty allow you to input your pager rotation and then define good rules for how to contact the on call engineer and when to escalate should the engineer be unavailable.
  1. With improved monitoring and alerting in place, you may want to think about giving certain customers “911” access. At a previous company I worked at, we had a secret email address our big customers could hit which would open a support ticket and then page the on call engineer with the ticket number. If you decide to go this route; however, you’ll want to train your customers when it’s appropriate to use this power and how to use it most effectively.

  2. Adjust alerts and fix problems as you get paged for them. Don’t care that a particular API goes down during a known maintenance window? Schedule the notification policy accordingly.

  3. Finally, continue maintaining your inventory and monitoring service’s configuration. For extra benefit, consider tracking your organization’s Mean Time To Respond (how long it took for engineer to acknowledge that something is wrong) and your Mean Time To Recover (how long it took the engineer to resolve the issue including the Mean Time To Respond), your Mean Time Between Failures (self-explanatory, I hope), and Percent Availability (what percent of time your service is functional in a given period of time).

This concludes the management and non-ops introduction to operations; I hope you find this helpful.

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