Automatic merge from submit-queue
Enable shared PID namespace by default for docker pods
**What this PR does / why we need it**: This PR enables PID namespace sharing for docker pods by default, bringing the behavior of docker in line with the other CRI runtimes when used with docker >= 1.13.1.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: ref #1615
**Special notes for your reviewer**: cc @dchen1107 @yujuhong
**Release note**:
```release-note
Kubernetes now shares a single PID namespace among all containers in a pod when running with docker >= 1.13.1. This means processes can now signal processes in other containers in a pod, but it also means that the `kubectl exec {pod} kill 1` pattern will cause the pod to be restarted rather than a single container.
```
Automatic merge from submit-queue
Delete "hard-coded" default value in flags usage.
**What this PR does / why we need it**:
Some flags of kubernetes components have "hard-coded" default values in their usage info. In fact, [pflag pkg](https://github.com/kubernetes/kubernetes/blob/master/vendor/github.com/spf13/pflag/flag.go#L602-L608) has already added a string `(default value)` automatically in the usage info if the flag is initialized. Then we don't need to hard-code the default value in usage info. After this PR, if we want to update the default value of a flag, we only need to update the flag where it is initialized. `pflag` will update the usage info for us. This will avoid inconsistency.
For example:
Before
```
kubelet -h
...
--node-status-update-frequency duration Specifies how often kubelet posts node status to master. Note: be cautious when changing the constant, it must work with nodeMonitorGracePeriod in nodecontroller. Default: 10s (default 10s)
...
```
After
```
kubelet -h
...
--node-status-update-frequency duration Specifies how often kubelet posts node status to master. Note: be cautious when changing the constant, it must work with nodeMonitorGracePeriod in nodecontroller. (default 10s)
...
```
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
This PR doesn't delete some "hard-coded" default values because they are not explicitly initialized. We still need to hard-code them to give users friendly info.
```
--allow-privileged If true, allow containers to request privileged mode. [default=false]
```
**Release note**:
```release-note
None
```
Kubelet flags are not necessarily appropriate for the KubeletConfiguration
object. For example, this PR also removes HostnameOverride and NodeIP
from KubeletConfiguration. This is a preleminary step to enabling Nodes
to share configurations, as part of the dynamic Kubelet configuration
feature (#29459). Fields that must be unique for each node inhibit
sharing, because their values, by definition, cannot be shared.
Automatic merge from submit-queue
kubelet: change image-gc-high-threshold below docker dm.min_free_space
docker dm.min_free_space defaults to 10%, which "specifies the min free space percent in a thin pool require for new device creation to succeed....Whenever a new a thin pool device is created (during docker pull or during container creation), the Engine checks if the minimum free space is available. If sufficient space is unavailable, then device creation fails and any relevant docker operation fails." [1]
This setting is preventing the storage usage to cross the 90% limit. However, image GC is expected to kick in only beyond image-gc-high-threshold. The image-gc-high-threshold has a default value of 90%, and hence GC never triggers. If image-gc-high-threshold is set to a value lower than (100 - dm.min_free_space)%, GC triggers.
xref https://bugzilla.redhat.com/show_bug.cgi?id=1408309
```release-note
changed kubelet default image-gc-high-threshold to 85% to resolve a conflict with default settings in docker that prevented image garbage collection from resolving low disk space situations when using devicemapper storage.
```
@derekwaynecarr @sdodson @rhvgoyal
Automatic merge from submit-queue
Use realistic value for the memory example of kube-reserved and system-reserved
Use realistic value for the memory example of kube-reserved and system-reserved
Currently, kublet help shows the memory example of
kube-reserved and system-reserved as 150G. This 150G is not realistic
value and it leads misconfiguration or confusion. This patch changes
to example value as 500Mi.
Before(same with system-reserved):
```
--kube-reserved value A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=150G) pairs that describe resources reserved for kubernetes system components. Currently only cpu and memory are supported. See http://releases.k8s.io/HEAD/docs/user-guide/compute-resources.md for more detail. [default=none]
```
After(same with system-reserved):
```
--kube-reserved value A set of ResourceName=ResourceQuantity (e.g. cpu=200m,memory=500Mi) pairs that describe resources reserved for kubernetes system components. Currently only cpu and memory are supported. See http://releases.k8s.io/HEAD/docs/user-guide/compute-resources.md for more detail. [default=none]
```
Automatic merge from submit-queue (batch tested with PRs 41919, 41149, 42350, 42351, 42285)
enable cgroups tiers and node allocatable enforcement on pods by default.
```release-note
Pods are launched in a separate cgroup hierarchy than system services.
```
Depends on #41753
cc @derekwaynecarr
Automatic merge from submit-queue
Allow multipe DNS servers as comma-seperated argument for kubelet --dns
This PR explores how kubectls "--dns" could be extended to specify multiple DNS servers for in-cluster PODs. Testing on the local libvirt-coreos cluster shows that multiple DNS server are injected without issues.
Specifying multiple DNS servers increases resilience against
- Packet drops
- Single server failure
I am debugging services that do 50+ DNS requests for a single incoming interactive request, thus highly increase the chance of a slowdown (+5s) due to a single packet drop. Switching to two DNS servers will reduce the impact of the issues (roughly +1s on glibc, 0s on musl, error-rate goes down to error-rate^2).
Note that there is no need to change any runtime related code as far as I know. In the case of "default" dns the /etc/resolv.conf is parsed and multiple DNS server are send to the backend anyway. This only adds the same capability for the clusterFirst case.
I've heard from @thockin that multiple DNS entries are somehow considered. I've no idea what was considered, though. This is what I would like to see for our production use, though.
```release-note
NONE
```
Automatic merge from submit-queue
Switch resourcequota controller to shared informers
Originally part of #40097
I have had some issues with this change in the past, when I updated `pkg/quota` to use the new informers while `pkg/controller/resourcequota` remained on the old informers. In this PR, both are switched to using the new informers. The issues in the past were lots of flakey test failures in the ResourceQuota e2es, where it would randomly fail to see deletions and handle replenishment. I am hoping that now that everything here is consistently using the new informers, there won't be any more of these flakes, but it's something to keep an eye out for.
I also think `pkg/controller/resourcequota` could be cleaned up. I don't think there's really any need for `replenishment_controller.go` any more since it's no longer running individual controllers per kind to replenish. It instead just uses the shared informer and adds event handlers to it. But maybe we do that in a follow up.
cc @derekwaynecarr @smarterclayton @wojtek-t @deads2k @sttts @liggitt @timothysc @kubernetes/sig-scalability-pr-reviews
This change makes kubelet to use the CRI implementation by default,
unless the users opt out explicitly by using --enable-cri=false.
For the rkt integration, the --enable-cri flag will have no effect
since rktnetes does not use CRI.
Also, mark the original --experimental-cri flag hidden and deprecated,
so that we can remove it in the next release.
Depending on an exact cluster setup multiple dns may make sense.
Comma-seperated lists of DNS server are quite common as DNS servers
are always plain IPs.
Automatic merge from submit-queue (batch tested with PRs 40251, 40171)
Mark --docker-exec-handler deprecated
We plan to drop support for the nsenter exec handler in the future. Marking this flag as deprecated to warn the users.
Dong Liu