nomad-autoscaler-plugin-apm-metrics

README

Nomad Autoscaler APM plugin for "Metrics" endpoints

An APM plugin that regularly collects metrics from a metrics endpoint and provides its values to the Nomad Autoscaler. It is a standalone solution without the need of an external time series DB to collect the metrics and thus an alternative to using the Prometheus APM plugin or the influx APM plugin.

Configuration

Part of the Nomad autoscaler configuration:

apm "app-metrics" {
  driver = "metrics"
  config = {
    url = "https://app/metrics"
    header_authorization = "Bearer abc"
    refresh = "10"
    retention = "60"
  }
}

The refresh value is how often the metrics are collected from the endpoint (in seconds).

The retention value is how long the metrics are kept in memory (in minutes).

Usage in Nomad job definitions

job "webapp" {
  ...
  group "demo" {
    ...
    scaling {
      enabled = true
      min = 1
      max = 2
      ...
      policy {
        check "scalecheck" {
          source = "app-metrics"
          query = "metrics"  # the name of the metric to use, this needs to include the tag if there is one, f.e. metrics{tag="a"}. If there is more than one tag, the order in which the tags are given needs to be alphabetically increasing, f.e. metrics{tag1="a",tag2="b"}

          strategy "threshold" {
            ...
          }
        }
      }
    }
  }
}

For now, metrics with tags can only be queried with all tags given, i.e. there are no aggregates across tags.