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DevOps measurement: Proactive failure notification

Proactive failure notification is the practice of generating notifications when monitored values approach known failure thresholds, and not waiting for the system to alert you it has already failed — or worse, to find out from customers that your application or service is down. Using this approach, you can identify and potentially resolve issues before they become serious or start to impact your users. The 2014 DevOps Research and Assessment (DORA) (PDF) research showed that proactive monitoring is a significant predictor of software delivery performance. According to DORA research, teams that use proactive notification can diagnose and solve problems quickly. When failures are instead primarily reported by a source external to the operations team, such as by the network operations center (NOC) — or worse, by customers — rather than internal monitoring, performance suffers.

How to implement proactive failure notification

Use alerting rules. You should generate failure notifications using specific alerting rules. Alerting rules define the conditions under which an alert is generated and the notification channel for that alert.

Use thresholds. Alerting rules should use thresholds for the metrics you monitor that indicate real trouble. Monitoring thresholds trigger alerting rules, which generate notifications when metric levels cross threshold values.

Choose thresholds carefully. Choose thresholds to only generate alerts when the threshold actually predicts an issue. That is, don't arbitrarily select a value. Generally, you should identify which value levels begin to cause user-facing impact, and then trigger an alert notification at some percentage before that value is crossed.

For example, you might choose to trigger an alert notification when average response time for pages is within 20% of a threshold at which you know users start becoming frustrated and calling support.

Hold incident post-mortems. When you hold post-mortems following incidents, determine which indicators could have predicted the incident and monitor them in the future.

Plan a notification strategy. If a notification requires no action or the same action every time, you should automate the response. You should also consider the volume of notifications for events. A deluge of notifications during an event might be distracting rather than useful. When people are exposed to a large number of alarms, they can become desensitized to them (a problem known as "alert fatigue") leading to longer response times or missed alarms. Regularly review notifications and delete those that cannot be acted upon.

Ways to improve failure notification

Configure alerts to notify your key teams when something goes wrong in your systems early, long before it moves to the Network Operations Center (NOC) or to a customer. Tactics include:

  • Configuring alerts in logging and monitoring systems to appropriate levels.
  • Configuring alerts to make sure they notify people and teams who can fix the problem.
  • Proactively monitoring system health based on best practice threshold warnings.
  • Proactively monitoring system health based on rate of change warnings.
  • Ensuring that only relevant alerts are occurring, and that the team isn't receiving too many alerts. Take a hard look at which alerts are irrelevant. Disable irrelevant alerts and turn relevant monitoring alerts back on. Disabling all alerts is bad practice.

Ways to measure failure notifications

Instrumenting proactive monitoring is straightforward. The components to capture are:

  1. The extent to which failure alerts from logging and monitoring systems are captured and used.
  2. The extent to which system health is proactively monitored using threshold warnings.
  3. The extent to which system health is proactively monitored using rate of change warnings.

To make sure you are capturing different aspects of your system, you should monitor metrics in at least two different ways. For example, you might set a metric threshold that triggers alerts if a metric rises or falls below a value over a given time window, and a rate of change, which triggers alerts when a metric value change rate is higher or lower than expected.

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