Aergia

In Greek mythology, Aergia is the personification of sloth, idleness, indolence and laziness

Aergia is a controller that can be used to scale deployments from zero when a request is made to an ingress with a zero scaled deployment.

This controller replaces the ingress-nginx default backend with this custom backend.

This backend is designed to serve generic error handling for any http error. The backend can also leverage custom errors, which can be used to check the kubernetes api to see if the namespace needs to be scaled from zero.

Usage

An environment can be force idled, force scaled, or unidled using labels on the namespace. All actions still respect the label selectors, but forced actions will bypass any hits checks

Force Idled

To force idle a namespace, you can label the namespace using idling.amazee.io/force-idled=true. This will cause the environment to be immediately scaled down, but the next request to the ingress in the namespace will unidle the namespace

Force Scaled

To force scale a namespace, you can label the namespace using idling.amazee.io/force-scaled=true. This will cause the environment to be immediately scaled down, but the next request to the ingress in the namespace will NOT unidle the namespace. A a deployment will be required to unidle this namespace

Unidle

To unidle a namespace, you can label the namespace using idling.amazee.io/unidle=true. This will cause the environment to be scaled back up to its previous state.

Change the default templates

By using the environment variable ERROR_FILES_PATH, and pointing to a location that contains the three templates error.html, forced.html, and unidle.html, you can change what is shown to the end user.

This could be done using a configmap and volume mount to any directory, then update the ERROR_FILES_PATH to this directory.

Installation

Install via helm (https://github.com/amazeeio/charts/tree/main/charts/aergia)

Custom templates

If installing via helm, you can use this YAML in your values.yaml file and define the templates there.

See www/error.html, www/forced.html, and www/unidle.html for inspiration

templates:
  enabled: false
  error: |
    {{define "base"}}
    <html>
    <body>
    {{ .ErrorCode }} {{ .ErrorMessage }}
    </body>
    </html>
    {{end}}
  unidle: |
    {{define "base"}}
    <html>
    <head>
    <meta http-equiv="refresh" content="{{ .RefreshInterval }}">
    </head>
    <body>
    {{ .ErrorCode }} {{ .ErrorMessage }}
    </body>
    </html>
    {{end}}
  forced: |
    {{define "base"}}
    <html>
    <head>
    </head>
    <body>
    {{ .ErrorCode }} {{ .ErrorMessage }}
    </body>
    </html>
    {{end}}

Prometheus

The idler uses prometheus to check if there has been hits to the ingress in the last defined interval, it only checks status codes of 200. By default it will talk to a prometheus in cluster http://monitoring-kube-prometheus-prometheus.monitoring.svc:9090 but this is adjustable with a flag (and via helm values).

Requirements

One of the requirements of using prometheus is the ability to query for ingress-nginx requests using this metric nginx_ingress_controller_requests

You need to ensure that your ingress-nginx controller is scraped for this metric or else the idler will assume there have been 0 hits and idle the environment without hesitation.

An example ServiceMonitor is found in this repo under test-resources/ingress-servicemonitor.yaml

amazeeio/aergia-controller