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Scale down Kubernetes deployments after work hours
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README.rst

Kubernetes Downscaler

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Scale down Kubernetes deployments and/or statefulsets during non-work hours.

Deployments are interchangeable by statefulset for this whole guide.

It will scale down the deployment's replicas if all of the following conditions are met:

  • current time is not part of the "uptime" schedule or current time is part of the "downtime" schedule. The schedules are being evaluated in following order:
    • downscaler/downscale-period or downscaler/downtime annotation on the deployment/stateful set
    • downscaler/upscale-period or downscaler/uptime annotation on the deployment/stateful set
    • downscaler/downscale-period or downscaler/downtime annotation on the deployment/stateful set's namespace
    • downscaler/upscale-period or downscaler/uptime annotation on the deployment/stateful set's namespace
    • --upscale-period or --default-uptime cli argument
    • --downscale-period or --default-downtime cli argument
    • UPSCALE_PERIOD or DEFAULT_UPTIME environment variable
    • DOWNSCALE_PERIOD or DEFAULT_DOWNTIME environment variable
  • the deployment's namespace is not part of the exclusion list (kube-system is excluded by default)
  • the deployment's name is not part of the exclusion list
  • the deployment is not marked for exclusion (annotation downscaler/exclude: "true")
  • there are no active pods that force the whole cluster into uptime (annotation downscaler/force-uptime: "true")

The deployment by default will be scaled down to zero replicas. This can be configured with a deployment or its namespace's annotation of downscaler/downtime-replicas (e.g. downscaler/downtime-replicas: "1") or via CLI with --downtime-replicas.

Example use cases:

  • Deploy the downscaler to a test (non-prod) cluster with a default uptime or downtime time range to scale down all deployments during the night and weekend.
  • Deploy the downscaler to a production cluster without any default uptime/downtime setting and scale down specific deployments by setting the downscaler/uptime (or downscaler/downtime) annotation. This might be useful for internal tooling frontends which are only needed during work time.

You need to combine the downscaler with an elastic cluster autoscaler to actually save cloud costs. The official cluster autoscaler and the kube-aws-autoscaler were tested to work fine with the downscaler.

Usage

Deploy the downscaler into your cluster via (also works with kind or Minikube):

$ kubectl apply -f deploy/

The example configuration uses the --dry-run as a safety flag to prevent downscaling --- remove it to enable the downscaler, e.g. by editing the deployment:

$ kubectl edit deploy kube-downscaler

The example deployment manifests come with a configured uptime (deploy/config.yaml sets it to "Mon-Fri 07:30-20:30 CET"), you can overwrite this per namespace or deployment, e.g.:

$ kubectl run nginx --image=nginx
$ kubectl annotate deploy nginx 'downscaler/uptime=Mon-Fri 09:00-17:00 America/Buenos_Aires'

Note that the default grace period of 15 minutes applies to the new nginx deployment, i.e. if the current time is not within Mon-Fri 9-17 (Buenos Aires timezone), it will downscale not immediately, but after 15 minutes. The downscaler will eventually log something like:

INFO: Scaling down Deployment default/nginx from 1 to 0 replicas (uptime: Mon-Fri 09:00-17:00 America/Buenos_Aires, downtime: never)

Configuration

The downscaler is configured via command line args, environment variables and/or Kubernetes annotations.

Time definitions (e.g. DEFAULT_UPTIME) accept a comma separated list of specifications, e.g. the following configuration would downscale all deployments for non-work hours:

DEFAULT_UPTIME="Mon-Fri 07:30-20:30 Europe/Berlin"

To only downscale during the weekend and Friday after 20:00:

DEFAULT_DOWNTIME="Sat-Sun 00:00-24:00 CET,Fri-Fri 20:00-24:00 CET'

Each time specification must have the format <WEEKDAY-FROM>-<WEEKDAY-TO-INCLUSIVE> <HH>:<MM>-<HH>:<MM> <TIMEZONE>. The timezone value can be any Olson timezone, e.g. "US/Eastern", "PST" or "UTC".

Alternative logic, based on periods

Instead of strict uptimes or downtimes, you can chose time periods for upscaling or downscaling. The time definitions are the same. In this case, the upscale or downscale happens only on time periods, rest of times will be ignored.

If upscale or downscale periods are configured, uptime and downtime will be ignored. This means that some options are mutually exclusive, e.g. you can either use --downscale-period or --default-downtime, but not both.

This definition will downscale your cluster between 19:00 and 20:00. If you upscale your cluster manually, it won't be scaled down until next day 19:00-20:00.

DOWNSCALE_PERIOD="Mon-Sun 19:00-20:00 Europe/Berlin"

Command Line Options

Available command line options:

--dry-run
Dry run mode: do not change anything, just print what would be done
--debug
Debug mode: print more information
--once
Run loop only once and exit
--interval
Loop interval (default: 30s)
--namespace
Namespace (default: all namespaces)
--include-resources
Downscale resources of this kind as comma separated list. [deployments, statefulsets, stacks] (default: deployments)
--grace-period
Grace period in seconds for new deployments before scaling them down (default: 15min). The grace period counts from time of creation of the deployment, i.e. updated deployments will immediately be scaled down regardless of the grace period.
--upscale-period
Alternative logic to scale up only in given period of time (default: never), can also be configured via environment variable UPSCALE_PERIOD or via the annotation downscaler/upscale-period on each deployment
--downscale-period
Alternative logic to scale down only in given period of time (default: never), can also be configured via environment variable DOWNSCALE_PERIOD or via the annotation downscaler/downscale-period on each deployment
--default-uptime
Default time range to scale up for (default: always), can also be configured via environment variable DEFAULT_UPTIME or via the annotation downscaler/uptime on each deployment
--default-downtime
Default time range to scale down for (default: never), can also be configured via environment variable DEFAULT_DOWNTIME or via the annotation downscaler/downtime on each deployment
--exclude-namespaces
Exclude namespaces from downscaling (default: kube-system), can also be configured via environment variable EXCLUDE_NAMESPACES
--exclude-deployments
Exclude specific deployments from downscaling (default: kube-downscaler, downscaler), can also be configured via environment variable EXCLUDE_DEPLOYMENTS
--exclude-statefulsets
Exclude specific statefulsets from statefulsets, can also be configured via environment variable EXCLUDE_STATEFULSETS
--downtime-replicas
Default value of replicas to downscale to, the annotation downscaler/downtime-replicas takes precedence over this value.

Namespace Defaults

DEFAULT_UPTIME, DEFAULT_DOWNTIME, FORCE_UPTIME and exclusion can also be configured using Namespace annotations. Where configured these values supersede the other global default values.

apiVersion: v1
kind: Namespace
metadata:
    name: foo
    labels:
        name: foo
    annotations:
        downscaler/uptime: Mon-Sun 07:30-18:00 CET

The following annotations are supported on the Namespace level:

  • downscaler/upscale-period
  • downscaler/downscale-period
  • downscaler/uptime
  • downscaler/downtime
  • downscaler/force-uptime
  • downscaler/exclude
  • downscaler/downtime-replicas

Contributing

Easiest way to contribute is to provide feedback! We would love to hear what you like and what you think is missing. Create an issue or ping try_except_ on Twitter.

PRs are welcome. Please also have a look at issues labeled with "help wanted".

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

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