Service Error Rate

The error rate for a service is a measure of how many errors that service is generating per second.

Note the error rate of a service is the sum of the error rates of each component within that service, so the metric should be considered relative to the historical value, rather than an absolute number.

This is probably best explained with an example: The web service is comprised of puma, workhorse and nginx components.

A single error in the puma component may bubble up and may be reported as three 500 errors - one in puma, one in workhorse and one in nginx. The error rate of the service is the sum of these values, so would report 3 for a single error bubbling up through the layers.

Service Availability Definitions

The definitions of service availability are defined in https://gitlab.com/gitlab-com/runbooks/blob/master/legacy-prometheus-rules/service_error_rate.yml