mirror of
https://github.com/k3s-io/kubernetes.git
synced 2025-10-31 05:40:42 +00:00
4ca66d2aef
Stop munger produce the link to a release version doc if it doesn't exit in the release branch
111 lines
4.8 KiB
Markdown
111 lines
4.8 KiB
Markdown
<!-- BEGIN MUNGE: UNVERSIONED_WARNING -->
|
|
|
|
<!-- BEGIN STRIP_FOR_RELEASE -->
|
|
|
|
<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
|
|
width="25" height="25">
|
|
<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
|
|
width="25" height="25">
|
|
<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
|
|
width="25" height="25">
|
|
<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
|
|
width="25" height="25">
|
|
<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
|
|
width="25" height="25">
|
|
|
|
<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>
|
|
|
|
If you are using a released version of Kubernetes, you should
|
|
refer to the docs that go with that version.
|
|
|
|
<!-- TAG RELEASE_LINK, added by the munger automatically -->
|
|
<strong>
|
|
The latest release of this document can be found
|
|
[here](http://releases.k8s.io/release-1.1/docs/admin/garbage-collection.md).
|
|
|
|
Documentation for other releases can be found at
|
|
[releases.k8s.io](http://releases.k8s.io).
|
|
</strong>
|
|
--
|
|
|
|
<!-- END STRIP_FOR_RELEASE -->
|
|
|
|
<!-- END MUNGE: UNVERSIONED_WARNING -->
|
|
|
|
# Garbage Collection
|
|
|
|
- [Introduction](#introduction)
|
|
- [Image Collection](#image-collection)
|
|
- [Container Collection](#container-collection)
|
|
- [User Configuration](#user-configuration)
|
|
|
|
### Introduction
|
|
|
|
Garbage collection is managed by kubelet automatically, mainly including unreferenced
|
|
images and dead containers. kubelet applies container garbage collection every minute
|
|
and image garbage collection every 5 minutes.
|
|
Note that we don't recommend external garbage collection tool generally, since it could
|
|
break the behavior of kubelet potentially if it attempts to remove all of the containers
|
|
which acts as the tombstone kubelet relies on. Yet those garbage collector aims to deal
|
|
with the docker leaking issues would be appreciated.
|
|
|
|
### Image Collection
|
|
|
|
kubernetes manages lifecycle of all images through imageManager, with the cooperation
|
|
of cadvisor.
|
|
The policy for garbage collecting images we apply takes two factors into consideration,
|
|
`HighThresholdPercent` and `LowThresholdPercent`. Disk usage above the high threshold
|
|
will trigger garbage collection, which attempts to delete unused images until the low
|
|
threshold is met. Least recently used images are deleted first.
|
|
|
|
### Container Collection
|
|
|
|
The policy for garbage collecting containers we apply takes on three variables, which can
|
|
be user-defined. `MinAge` is the minimum age at which a container can be garbage collected,
|
|
zero for no limit. `MaxPerPodContainer` is the max number of dead containers any single
|
|
pod (UID, container name) pair is allowed to have, less than zero for no limit.
|
|
`MaxContainers` is the max number of total dead containers, less than zero for no limit as well.
|
|
|
|
kubelet sorts out containers which are unidentified or stay out of bounds set by previous
|
|
mentioned three flags. Generally the oldest containers are removed first. Since we take both
|
|
`MaxPerPodContainer` and `MaxContainers` into consideration, it could happen when they
|
|
have conflict -- retaining the max number of containers per pod goes out of range set by max
|
|
number of global dead containers. In this case, we would sacrifice the `MaxPerPodContainer`
|
|
a little bit. For the worst case, we first downgrade it to 1 container per pod, and then
|
|
evict the oldest containers for the greater good.
|
|
|
|
When kubelet removes the dead containers, all the files inside the container will be cleaned up as well.
|
|
Note that we will skip the containers that are not managed by kubelet.
|
|
|
|
### User Configuration
|
|
|
|
Users are free to set their own value to address image garbage collection.
|
|
|
|
1. `image-gc-high-threshold`, the percent of disk usage which triggers image garbage collection.
|
|
Default is 90%.
|
|
2. `image-gc-low-threshold`, the percent of disk usage to which image garbage collection attempts
|
|
to free. Default is 80%.
|
|
|
|
We also allow users to customize garbage collection policy, basically via following three flags.
|
|
|
|
1. `minimum-container-ttl-duration`, minimum age for a finished container before it is
|
|
garbage collected. Default is 1 minute.
|
|
2. `maximum-dead-containers-per-container`, maximum number of old instances to retain
|
|
per container. Default is 2.
|
|
3. `maximum-dead-containers`, maximum number of old instances of containers to retain globally.
|
|
Default is 100.
|
|
|
|
Note that we highly recommend a large enough value for `maximum-dead-containers-per-container`
|
|
to allow at least 2 dead containers retaining per expected container when you customize the flag
|
|
configuration. A loose value for `maximum-dead-containers` also assumes importance for a similar reason.
|
|
See [this issue](https://github.com/kubernetes/kubernetes/issues/13287) for more details.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
|
|
[]()
|
|
<!-- END MUNGE: GENERATED_ANALYTICS -->
|