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Merge pull request #6630 from scjane/patch-20

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Update out-of-resource.md
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Qiming
2017-12-12 08:59:12 +08:00
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docs/tasks/administer-cluster/out-of-resource.md
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@@ -19,8 +19,8 @@ nodes become unstable.
## Eviction Policy ## Eviction Policy
The `kubelet` can proactively monitor for and prevent total starvation of a The `kubelet` can proactively monitor for and prevent total starvation of a
compute resource. In those cases, the `kubelet` can reclaim the starved compute resource. In those cases, the `kubelet` can reclaim the starved
resource by proactively failing one or more Pods. When the `kubelet` fails resource by proactively failing one or more Pods. When the `kubelet` fails
a Pod, it terminates all of its containers and transitions its `PodPhase` to `Failed`. a Pod, it terminates all of its containers and transitions its `PodPhase` to `Failed`.
### Eviction Signals ### Eviction Signals
@@ -42,11 +42,11 @@ The percentage based value is calculated relative to the total capacity
associated with each signal. associated with each signal.
The value for `memory.available` is derived from the cgroupfs instead of tools The value for `memory.available` is derived from the cgroupfs instead of tools
like `free -m`. This is important because `free -m` does not work in a like `free -m`. This is important because `free -m` does not work in a
container, and if users use the [node container, and if users use the [node
allocatable](/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable) feature, out of resource decisions allocatable](/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable) feature, out of resource decisions
are made local to the end user Pod part of the cgroup hierarchy as well as the are made local to the end user Pod part of the cgroup hierarchy as well as the
root node. This root node. This
[script](/docs/tasks/administer-cluster/out-of-resource/memory-available.sh) [script](/docs/tasks/administer-cluster/out-of-resource/memory-available.sh)
reproduces the same set of steps that the `kubelet` performs to calculate reproduces the same set of steps that the `kubelet` performs to calculate
`memory.available`. The `kubelet` excludes inactive_file (i.e. # of bytes of `memory.available`. The `kubelet` excludes inactive_file (i.e. # of bytes of
@@ -60,7 +60,7 @@ memory is reclaimable under pressure.
container writable layers. container writable layers.
`imagefs` is optional. `kubelet` auto-discovers these filesystems using `imagefs` is optional. `kubelet` auto-discovers these filesystems using
cAdvisor. `kubelet` does not care about any other filesystems. Any other types cAdvisor. `kubelet` does not care about any other filesystems. Any other types
of configurations are not currently supported by the kubelet. For example, it is of configurations are not currently supported by the kubelet. For example, it is
*not OK* to store volumes and logs in a dedicated `filesystem`. *not OK* to store volumes and logs in a dedicated `filesystem`.
@@ -78,7 +78,7 @@ Each threshold has the following form:
where: where:
* `eviction-signal` is a eviction signal token as defined in the previous table. * `eviction-signal` is an eviction signal token as defined in the previous table.
* `operator` is the desired relational operator, such as `<` (less than). * `operator` is the desired relational operator, such as `<` (less than).
* `quantity` is the eviction threshhold quantity, such as `1Gi`. These tokens must * `quantity` is the eviction threshhold quantity, such as `1Gi`. These tokens must
match the quantity representation used by Kubernetes. An eviction threshold can also match the quantity representation used by Kubernetes. An eviction threshold can also
@@ -208,7 +208,7 @@ relative to their request for that resource are killed first. If no Pod
has exceeded its request, the strategy targets the largest consumer of the has exceeded its request, the strategy targets the largest consumer of the
starved resource. starved resource.
* `Guaranteed` Pods are guaranteed only when requests and limits are specified * `Guaranteed` Pods are guaranteed only when requests and limits are specified
for all the containers and they are equal A `Guaranteed` Pod is guaranteed to for all the containers and they are equal. A `Guaranteed` Pod is guaranteed to
never be evicted because of another Pod's resource consumption. If a system never be evicted because of another Pod's resource consumption. If a system
daemon (such as `kubelet`, `docker`, and `journald`) is consuming more resources daemon (such as `kubelet`, `docker`, and `journald`) is consuming more resources
than were reserved via `system-reserved` or `kube-reserved` allocations, and the than were reserved via `system-reserved` or `kube-reserved` allocations, and the
@@ -322,7 +322,7 @@ and trigger eviction assuming those Pods use less than their configured request.
### DaemonSet ### DaemonSet
It is never desired for a `kubelet` to evict a `DaemonSet` Pod, since the Pod is It is never desired for `kubelet` to evict a `DaemonSet` Pod, since the Pod is
immediately recreated and rescheduled back to the same node. immediately recreated and rescheduled back to the same node.
At the moment, the `kubelet` has no ability to distinguish a Pod created At the moment, the `kubelet` has no ability to distinguish a Pod created