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Updated container garbage collection with accurate information #48001

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Updated container garbage collection with accurate information #48001

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7f6ab53
updated container garbage policy current state
T-Lakshmi Sep 19, 2024
e661ab0
Corrected stylish nits
T-Lakshmi Sep 20, 2024
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20 changes: 14 additions & 6 deletions content/en/docs/concepts/architecture/garbage-collection.md
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Expand Up @@ -166,17 +166,25 @@ is restarted, the tracked image age is reset, causing the kubelet to wait the fu
based on image age.
{{< /note>}}

### Container garbage collection {#container-image-garbage-collection}
### Container garbage collection {#container-image-garbage-collection} (deprecated)

{{< caution >}}
Container garbage collection is deprecated in favour of `--eviction-hard` or
`--eviction-soft` and will be removed in a future version. For more details on
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container gc and eviction are different things ...

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Hello @tengqm,

container gc and eviction are different things ...

Can you clarify on the below points of container gc?

  1. Is --minimum-container-ttl-duration, --maximum-dead-containers and --maximum-dead-containers-per-container related to container gc?
  2. In which version container gc got deprecated?
  3. Is there any alternate recommended way for container garbage collection? What it is?

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Container GC is a task performed by kubelet regularly. The command line flags you mentioned are about container GC. The things that got deprecated, IIRC, are the command line flags. The intent of the deprecation was to reduce knobs for users to tune.
With the mechanism still there in kubelet, container GC won't go away any time soon. I'm not aware of anyone pushing this forward. In other words, the "deprecation" itself may get rotten (or deprecated).

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Thanks for sharing feedback @tengqm.

What others say on this? Please share your opinion.

eviction policy, see [node-pressure-eviction](/docs/concepts/scheduling-eviction/node-pressure-eviction/).
{{< /caution >}}
Comment on lines +169 to +175
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@sftim sftim Sep 20, 2024 •
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These command line arguments are deprecated, and the format isn't right.
We also avoid statements about the future, although we do make reasonable exceptions to that general guidance.

Try this:

Suggested change
### Container garbage collection {#container-image-garbage-collection} (deprecated)
{{< caution >}}
Container garbage collection is deprecated in favour of `--eviction-hard` or
`--eviction-soft` and will be removed in a future version. For more details on
eviction policy, see [node-pressure-eviction](/docs/concepts/scheduling-eviction/node-pressure-eviction/).
{{< /caution >}}
### Legacy garbage collection for containers (deprecated) {#container-image-garbage-collection}
{{< feature-state for_k8s_version="v1.9" state="deprecated" >}}
{{< note >}}
Container garbage collection is deprecated, in favor of using the kubelet configuration file
entries `evictionHard` and `evictionSoft` to manage overall Pod
{{< glossary_tooltip text="eviction" term_id="eviction" >}}.
{{< /note >}}

ℹ️ I am not sure about which version deprecated setting these command line arguments.

Am I right that eviction is always at the Pod level, whereas these deprecated settings apply at the container level?


The kubelet garbage collects unused containers based on the following variables,
which you can define:

* `MinAge`: the minimum age at which the kubelet can garbage collect a
container. Disable by setting to `0`.
* `MaxPerPodContainer`: the maximum number of dead containers each Pod
can have. Disable by setting to less than `0`.
* `MinAge`: the minimum age at which the kubelet can garbage collect a container.
Disable by setting a kubelet config flag `--minimum-container-ttl-duration` to `0`.
* `MaxPerPodContainer`: the maximum number of dead containers each Pod can have.
Disable by setting a kubelet config flag `--maximum-dead-containers-per-container`
to less than `0`.
* `MaxContainers`: the maximum number of dead containers the cluster can have.
Disable by setting to less than `0`.
Disable by setting a kubelet config flag `--maximum-dead-containers`
to less than `0`.
Comment on lines 177 to +187
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@sftim sftim Sep 20, 2024 •
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Is this right?

Suggested change
The kubelet garbage collects unused containers based on the following variables,
which you can define:
* `MinAge`: the minimum age at which the kubelet can garbage collect a
container. Disable by setting to `0`.
* `MaxPerPodContainer`: the maximum number of dead containers each Pod
can have. Disable by setting to less than `0`.
* `MinAge`: the minimum age at which the kubelet can garbage collect a container.
Disable by setting a kubelet config flag `--minimum-container-ttl-duration` to `0`.
* `MaxPerPodContainer`: the maximum number of dead containers each Pod can have.
Disable by setting a kubelet config flag `--maximum-dead-containers-per-container`
to less than `0`.
* `MaxContainers`: the maximum number of dead containers the cluster can have.
Disable by setting to less than `0`.
Disable by setting a kubelet config flag `--maximum-dead-containers`
to less than `0`.
The kubelet garbage collects dead containers within existing Pods. This garbage collection is
based on the values for several related command line arguments, that are all deprecated:
`--minimum-container-ttl-duration`
: the minimum age at which the kubelet can garbage collect a dead container. Disable by setting to 0. Setting a value for `--minimum-container-ttl-duration` is deprecated.
`--maximum-dead-containers`
: limits the total number of dead containers for this node. The default is unlimited. You can set this to an integer that is zero or higher in order to set legacy dead container limits, node-wide. Setting a value for `--maximum-dead-containers` is deprecated.
`--maximum-dead-containers-per-container`: the maximum number of dead containers each Pod
can have. The default value for this setting is 1; however, you can specify unlimited dead containers by setting this value to 0. Note that setting a value for `--maximum-dead-containers-per-container` is deprecated.

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yeah I agree we should refer folks to the kubelet configuration options as we're redirecting folks away from using the CLI

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WDYT ^ @T-Lakshmi ?

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@haircommander,
Yes, I also agree to mention about CLI usage of these arguments.

But my concern is the below statement is true or not?

Container garbage collection is deprecated in favour of --eviction-hard or --eviction-soft and will be removed in a future version.

also when container GC got deprecated and what are the recommended way to use as alternate to container GC?

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Also here it mentioned old logs are stored outside of container's context.

Is that true? if true, in which location old logs are storing now?
Please share your inputs.


In addition to these variables, the kubelet garbage collects unidentified and
deleted containers, typically starting with the oldest first.
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