Scale down Kubernetes deployments after work hours
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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" or downscaler/exclude-until: "2024-04-05")
  • 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):

In case you are deploying kube-downscaler to another namespace than default, for example if your context is pointing to my-namespace. Make sure you change the deploy/rbac.yaml Service Account configuration namespace: default to the destination namespace my-namespace, instead of default.

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:

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.:

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:

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

Each time specification can be in one of two formats:

  • Recurring specifications 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".
  • Absolute specifications have the format <TIME_FROM>-<TIME_TO> where each <TIME> is an ISO 8601 date and time of the format <YYYY>-<MM>-<DD>T<HH>:<MM>:<SS>[+-]<TZHH>:<TZMM>.

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.

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

Restrict the downscaler to work only in a single namespace (default: all namespaces). This is mainly useful for deployment scenarios where the deployer of kube-downscaler only has access to a given namespace (instead of cluster access).

--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.

--deployment-time-annotation

Optional: name of the annotation that would be used instead of the creation timestamp of the resource. This option should be used if you want the resources to be kept scaled up during a grace period (--grace-period) after a deployment. The format of the annotation's timestamp value must be exactly the same as for Kubernetes' creationTimestamp: %Y-%m-%dT%H:%M:%SZ. Recommended: set this annotation by your deployment tooling automatically.

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.

The following annotations are supported on the Namespace level:

  • downscaler/upscale-period
  • downscaler/downscale-period
  • downscaler/uptime
  • downscaler/downtime
  • downscaler/force-uptime
  • downscaler/exclude: set to true to exclude all resources in the namespace
  • downscaler/exclude-until: temporarily exclude all resources in the namespace until the given timestamp
  • downscaler/downtime-replicas: overwrite the default target replicas to scale down to (default: zero)

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/.