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Node PID limiting #12932

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Mar 16, 2019
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Node PID limiting #12932

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4 changes: 2 additions & 2 deletions content/en/docs/reference/command-line-tools-reference/kubelet.md
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Original file line number Diff line number Diff line change
Expand Up @@ -707,7 +707,7 @@ kubelet [flags]
<td colspan="2">--kube-reserved mapStringString</td>
</tr>
<tr>
<td></td><td style="line-height: 130%; word-wrap: break-word;">A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=500Mi,ephemeral-storage=1Gi) pairs that describe resources reserved for kubernetes system components. Currently cpu, memory and local ephemeral storage for root file system are supported. See http://kubernetes.io/docs/user-guide/compute-resources for more detail. [default=none]</td>
<td></td><td style="line-height: 130%; word-wrap: break-word;">A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=500Mi,ephemeral-storage=1Gi,pid=1000) pairs that describe resources reserved for kubernetes system components. Currently cpu, memory, pid, and local ephemeral storage for root file system are supported. See http://kubernetes.io/docs/user-guide/compute-resources for more detail. [default=none]</td>
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As this is reference documentation, I suspect that the right place to make this change is https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/apis/config/types.go#L294

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I did make that change there.

</tr>

<tr>
Expand Down Expand Up @@ -1092,7 +1092,7 @@ kubelet [flags]
<td colspan="2">--system-reserved mapStringString</td>
</tr>
<tr>
<td></td><td style="line-height: 130%; word-wrap: break-word;">A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=500Mi,ephemeral-storage=1Gi) pairs that describe resources reserved for non-kubernetes components. Currently only cpu and memory are supported. See http://kubernetes.io/docs/user-guide/compute-resources for more detail. [default=none]</td>
<td></td><td style="line-height: 130%; word-wrap: break-word;">A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=500Mi,ephemeral-storage=1Gi,pid=1000) pairs that describe resources reserved for non-kubernetes components. Currently only cpu, memory, and pid are supported. See http://kubernetes.io/docs/user-guide/compute-resources for more detail. [default=none]</td>
</tr>

<tr>
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15 changes: 12 additions & 3 deletions content/en/docs/tasks/administer-cluster/reserve-compute-resources.md
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Expand Up @@ -88,7 +88,7 @@ be configured to use the `systemd` cgroup driver.

### Kube Reserved

- **Kubelet Flag**: `--kube-reserved=[cpu=100m][,][memory=100Mi][,][ephemeral-storage=1Gi]`
- **Kubelet Flag**: `--kube-reserved=[cpu=100m][,][memory=100Mi][,][ephemeral-storage=1Gi][,][pid=1000]`
- **Kubelet Flag**: `--kube-reserved-cgroup=`

`kube-reserved` is meant to capture resource reservation for kubernetes system
Expand All @@ -102,6 +102,10 @@ post](https://kubernetes.io/blog/2016/11/visualize-kubelet-performance-with-node
explains how the dashboard can be interpreted to come up with a suitable
`kube-reserved` reservation.

In addition to `cpu`, `memory`, and `ephemeral-storage`, `pid` may be
specified to reserve the specified number of process IDs for
kubernetes system daemons.

To optionally enforce `kube-reserved` on system daemons, specify the parent
control group for kube daemons as the value for `--kube-reserved-cgroup` kubelet
flag.
Expand All @@ -118,7 +122,7 @@ exist. Kubelet will fail if an invalid cgroup is specified.

### System Reserved

- **Kubelet Flag**: `--system-reserved=[cpu=100m][,][memory=100Mi][,][ephemeral-storage=1Gi]`
- **Kubelet Flag**: `--system-reserved=[cpu=100m][,][memory=100Mi][,][ephemeral-storage=1Gi][,][pid=1000]`
- **Kubelet Flag**: `--system-reserved-cgroup=`


Expand All @@ -128,6 +132,10 @@ like `sshd`, `udev`, etc. `system-reserved` should reserve `memory` for the
Reserving resources for user login sessions is also recommended (`user.slice` in
systemd world).

In addition to `cpu`, `memory`, and `ephemeral-storage`, `pid` may be
specified to reserve the specified number of process IDs for OS system
daemons.

To optionally enforce `system-reserved` on system daemons, specify the parent
control group for OS system daemons as the value for `--system-reserved-cgroup`
kubelet flag.
Expand Down Expand Up @@ -182,7 +190,8 @@ container runtime. However, Kubelet cannot burst and use up all available Node
resources if `kube-reserved` is enforced.

Be extra careful while enforcing `system-reserved` reservation since it can lead
to critical system services being CPU starved or OOM killed on the node. The
to critical system services being CPU starved, OOM killed, or unable
to fork on the node. The
recommendation is to enforce `system-reserved` only if a user has profiled their
nodes exhaustively to come up with precise estimates and is confident in their
ability to recover if any process in that group is oom_killed.
Expand Down