Merge branch 'master' into dev-1.20

This commit is contained in:
Irvi Aini
2020-11-11 14:55:30 +01:00
committed by GitHub
168 changed files with 3843 additions and 3192 deletions
@@ -25,6 +25,7 @@ This page lists some of the available add-ons and links to their respective inst
* [Flannel](https://github.com/coreos/flannel/blob/master/Documentation/kubernetes.md) is an overlay network provider that can be used with Kubernetes.
* [Knitter](https://github.com/ZTE/Knitter/) is a plugin to support multiple network interfaces in a Kubernetes pod.
* [Multus](https://github.com/Intel-Corp/multus-cni) is a Multi plugin for multiple network support in Kubernetes to support all CNI plugins (e.g. Calico, Cilium, Contiv, Flannel), in addition to SRIOV, DPDK, OVS-DPDK and VPP based workloads in Kubernetes.
* [OVN-Kubernetes](https://github.com/ovn-org/ovn-kubernetes/) is a networking provider for Kubernetes based on [OVN (Open Virtual Network)](https://github.com/ovn-org/ovn/), a virtual networking implementation that came out of the Open vSwitch (OVS) project. OVN-Kubernetes provides an overlay based networking implementation for Kubernetes, including an OVS based implementation of load balancing and network policy.
* [OVN4NFV-K8S-Plugin](https://github.com/opnfv/ovn4nfv-k8s-plugin) is OVN based CNI controller plugin to provide cloud native based Service function chaining(SFC), Multiple OVN overlay networking, dynamic subnet creation, dynamic creation of virtual networks, VLAN Provider network, Direct provider network and pluggable with other Multi-network plugins, ideal for edge based cloud native workloads in Multi-cluster networking
* [NSX-T](https://docs.vmware.com/en/VMware-NSX-T/2.0/nsxt_20_ncp_kubernetes.pdf) Container Plug-in (NCP) provides integration between VMware NSX-T and container orchestrators such as Kubernetes, as well as integration between NSX-T and container-based CaaS/PaaS platforms such as Pivotal Container Service (PKS) and OpenShift.
* [Nuage](https://github.com/nuagenetworks/nuage-kubernetes/blob/v5.1.1-1/docs/kubernetes-1-installation.rst) is an SDN platform that provides policy-based networking between Kubernetes Pods and non-Kubernetes environments with visibility and security monitoring.
@@ -76,8 +76,7 @@ The following resource types are supported:
| `limits.memory` | Across all pods in a non-terminal state, the sum of memory limits cannot exceed this value. |
| `requests.cpu` | Across all pods in a non-terminal state, the sum of CPU requests cannot exceed this value. |
| `requests.memory` | Across all pods in a non-terminal state, the sum of memory requests cannot exceed this value. |
| `hugepages-<size>` | Across all pods in a non-terminal state, the number of
huge page requests of the specified size cannot exceed this value. |
| `hugepages-<size>` | Across all pods in a non-terminal state, the number of huge page requests of the specified size cannot exceed this value. |
| `cpu` | Same as `requests.cpu` |
| `memory` | Same as `requests.memory` |
@@ -237,7 +236,7 @@ one value. For example:
- middle
```
If the `operator` is `Exists` or `DoesNotExist`, the `values field must *NOT* be
If the `operator` is `Exists` or `DoesNotExist`, the `values` field must *NOT* be
specified.
### Resource Quota Per PriorityClass
@@ -91,7 +91,7 @@ To see which admission plugins are enabled:
kube-apiserver -h | grep enable-admission-plugins
```
In 1.18, they are:
In the current version, the default ones are:
```shell
NamespaceLifecycle, LimitRanger, ServiceAccount, TaintNodesByCondition, Priority, DefaultTolerationSeconds, DefaultStorageClass, StorageObjectInUseProtection, PersistentVolumeClaimResize, RuntimeClass, CertificateApproval, CertificateSigning, CertificateSubjectRestriction, DefaultIngressClass, MutatingAdmissionWebhook, ValidatingAdmissionWebhook, ResourceQuota
@@ -23,33 +23,33 @@ incomplete features are referred to in order to better describe service accounts
Kubernetes distinguishes between the concept of a user account and a service account
for a number of reasons:
- User accounts are for humans. Service accounts are for processes, which
run in pods.
- User accounts are intended to be global. Names must be unique across all
namespaces of a cluster, future user resource will not be namespaced.
Service accounts are namespaced.
- Typically, a cluster's User accounts might be synced from a corporate
database, where new user account creation requires special privileges and
is tied to complex business processes. Service account creation is intended
to be more lightweight, allowing cluster users to create service accounts for
specific tasks (i.e. principle of least privilege).
- Auditing considerations for humans and service accounts may differ.
- A config bundle for a complex system may include definition of various service
accounts for components of that system. Because service accounts can be created
ad-hoc and have namespaced names, such config is portable.
- User accounts are for humans. Service accounts are for processes, which run
in pods.
- User accounts are intended to be global. Names must be unique across all
namespaces of a cluster. Service accounts are namespaced.
- Typically, a cluster's user accounts might be synced from a corporate
database, where new user account creation requires special privileges and is
tied to complex business processes. Service account creation is intended to be
more lightweight, allowing cluster users to create service accounts for
specific tasks by following the principle of least privilege.
- Auditing considerations for humans and service accounts may differ.
- A config bundle for a complex system may include definition of various service
accounts for components of that system. Because service accounts can be created
without many constraints and have namespaced names, such config is portable.
## Service account automation
Three separate components cooperate to implement the automation around service accounts:
- A Service account admission controller
- A Token controller
- A Service account controller
- A `ServiceAccount` admission controller
- A Token controller
- A `ServiceAccount` controller
### Service Account Admission Controller
### ServiceAccount Admission Controller
The modification of pods is implemented via a plugin
called an [Admission Controller](/docs/reference/access-authn-authz/admission-controllers/). It is part of the apiserver.
called an [Admission Controller](/docs/reference/access-authn-authz/admission-controllers/).
It is part of the API server.
It acts synchronously to modify pods as they are created or updated. When this plugin is active
(and it is by default on most distributions), then it does the following when a pod is created or modified:
@@ -66,56 +66,78 @@ When the `BoundServiceAccountTokenVolume` feature gate is enabled, the service a
add a projected service account token volume instead of a secret volume. The service account token will expire after 1 hour by default or the pod is deleted. See more details about [projected volume](/docs/tasks/configure-pod-container/configure-projected-volume-storage/).
This feature depends on the `RootCAConfigMap` feature gate enabled which publish a "kube-root-ca.crt" ConfigMap to every namespace. This ConfigMap contains a CA bundle used for verifying connections to the kube-apiserver.
1. If the pod does not have a `serviceAccountName` set, it sets the
`serviceAccountName` to `default`.
1. It ensures that the `serviceAccountName` referenced by the pod exists, and
otherwise rejects it.
1. If the pod does not contain any `imagePullSecrets`, then `imagePullSecrets`
of the ServiceAccount referenced by `serviceAccountName` are added to the pod.
1. It adds a `volume` to the pod which contains a token for API access
if neither the ServiceAccount `automountServiceAccountToken` nor the Pod's
`automountServiceAccountToken` is set to `false`.
1. It adds a `volumeSource` to each container of the pod mounted at
`/var/run/secrets/kubernetes.io/serviceaccount`, if the previous step has
created a volume for ServiceAccount token.
You can migrate a service account volume to a projected volume when
the `BoundServiceAccountTokenVolume` feature gate is enabled.
The service account token will expire after 1 hour or the pod is deleted. See
more details about
[projected volume](/docs/tasks/configure-pod-container/configure-projected-volume-storage/).
### Token Controller
TokenController runs as part of controller-manager. It acts asynchronously. It:
TokenController runs as part of `kube-controller-manager`. It acts asynchronously. It:
- observes serviceAccount creation and creates a corresponding Secret to allow API access.
- observes serviceAccount deletion and deletes all corresponding ServiceAccountToken Secrets.
- observes secret addition, and ensures the referenced ServiceAccount exists, and adds a token to the secret if needed.
- observes secret deletion and removes a reference from the corresponding ServiceAccount if needed.
- watches ServiceAccount creation and creates a corresponding
ServiceAccount token Secret to allow API access.
- watches ServiceAccount deletion and deletes all corresponding ServiceAccount
token Secrets.
- watches ServiceAccount token Secret addition, and ensures the referenced
ServiceAccount exists, and adds a token to the Secret if needed.
- watches Secret deletion and removes a reference from the corresponding
ServiceAccount if needed.
You must pass a service account private key file to the token controller in the controller-manager by using
the `--service-account-private-key-file` option. The private key will be used to sign generated service account tokens.
Similarly, you must pass the corresponding public key to the kube-apiserver using the `--service-account-key-file`
option. The public key will be used to verify the tokens during authentication.
You must pass a service account private key file to the token controller in
the `kube-controller-manager` using the `--service-account-private-key-file`
flag. The private key is used to sign generated service account tokens.
Similarly, you must pass the corresponding public key to the `kube-apiserver`
using the `--service-account-key-file` flag. The public key will be used to
verify the tokens during authentication.
#### To create additional API tokens
A controller loop ensures a secret with an API token exists for each service
account. To create additional API tokens for a service account, create a secret
of type `ServiceAccountToken` with an annotation referencing the service
account, and the controller will update it with a generated token:
A controller loop ensures a Secret with an API token exists for each
ServiceAccount. To create additional API tokens for a ServiceAccount, create a
Secret of type `kubernetes.io/service-account-token` with an annotation
referencing the ServiceAccount, and the controller will update it with a
generated token:
secret.json:
Below is a sample configuration for such a Secret:
```json
{
"kind": "Secret",
"apiVersion": "v1",
"metadata": {
"name": "mysecretname",
"annotations": {
"kubernetes.io/service-account.name": "myserviceaccount"
}
},
"type": "kubernetes.io/service-account-token"
}
```yaml
apiVersion: v1
kind: Secret
metadata:
name: mysecretname
annotations:
kubernetes.io/service-account.name: myserviceaccount
type: kubernetes.io/service-account-token
```
```shell
kubectl create -f ./secret.json
kubectl create -f ./secret.yaml
kubectl describe secret mysecretname
```
#### To delete/invalidate a service account token
#### To delete/invalidate a ServiceAccount token Secret
```shell
kubectl delete secret mysecretname
```
### Service Account Controller
### ServiceAccount controller
A ServiceAccount controller manages the ServiceAccounts inside namespaces, and
ensures a ServiceAccount named "default" exists in every active namespace.
Service Account Controller manages ServiceAccount inside namespaces, and ensures
a ServiceAccount named "default" exists in every active namespace.
@@ -2,126 +2,122 @@
reviewers:
- davidopp
- lavalamp
title: Building large clusters
title: Considerations for large clusters
weight: 20
---
## Support
At {{< param "version" >}}, Kubernetes supports clusters with up to 5000 nodes. More specifically, we support configurations that meet *all* of the following criteria:
A cluster is a set of {{< glossary_tooltip text="nodes" term_id="node" >}} (physical
or virtual machines) running Kubernetes agents, managed by the
{{< glossary_tooltip text="control plane" term_id="control-plane" >}}.
Kubernetes {{< param "version" >}} supports clusters with up to 5000 nodes. More specifically,
Kubernetes is designed to accommodate configurations that meet *all* of the following criteria:
* No more than 100 pods per node
* No more than 5000 nodes
* No more than 150000 total pods
* No more than 300000 total containers
* No more than 100 pods per node
You can scale your cluster by adding or removing nodes. The way you do this depends
on how your cluster is deployed.
## Setup
## Cloud provider resource quotas {#quota-issues}
A cluster is a set of nodes (physical or virtual machines) running Kubernetes agents, managed by a "master" (the cluster-level control plane).
Normally the number of nodes in a cluster is controlled by the value `NUM_NODES` in the platform-specific `config-default.sh` file (for example, see [GCE's `config-default.sh`](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/gce/config-default.sh)).
Simply changing that value to something very large, however, may cause the setup script to fail for many cloud providers. A GCE deployment, for example, will run in to quota issues and fail to bring the cluster up.
When setting up a large Kubernetes cluster, the following issues must be considered.
### Quota Issues
To avoid running into cloud provider quota issues, when creating a cluster with many nodes, consider:
* Increase the quota for things like CPU, IPs, etc.
* In [GCE, for example,](https://cloud.google.com/compute/docs/resource-quotas) you'll want to increase the quota for:
To avoid running into cloud provider quota issues, when creating a cluster with many nodes,
consider:
* Request a quota increase for cloud resources such as:
* Computer instances
* CPUs
* VM instances
* Total persistent disk reserved
* Storage volumes
* In-use IP addresses
* Firewall Rules
* Forwarding rules
* Routes
* Target pools
* Gating the setup script so that it brings up new node VMs in smaller batches with waits in between, because some cloud providers rate limit the creation of VMs.
* Packet filtering rule sets
* Number of load balancers
* Network subnets
* Log streams
* Gate the cluster scaling actions to brings up new nodes in batches, with a pause
between batches, because some cloud providers rate limit the creation of new instances.
### Etcd storage
## Control plane components
To improve performance of large clusters, we store events in a separate dedicated etcd instance.
For a large cluster, you need a control plane with sufficient compute and other
resources.
When creating a cluster, existing salt scripts:
Typically you would run one or two control plane instances per failure zone,
scaling those instances vertically first and then scaling horizontally after reaching
the point of falling returns to (vertical) scale.
You should run at least one instance per failure zone to provide fault-tolerance. Kubernetes
nodes do not automatically steer traffic towards control-plane endpoints that are in the
same failure zone; however, your cloud provider might have its own mechanisms to do this.
For example, using a managed load balancer, you configure the load balancer to send traffic
that originates from the kubelet and Pods in failure zone _A_, and direct that traffic only
to the control plane hosts that are also in zone _A_. If a single control-plane host or
endpoint failure zone _A_ goes offline, that means that all the control-plane traffic for
nodes in zone _A_ is now being sent between zones. Running multiple control plane hosts in
each zone makes that outcome less likely.
### etcd storage
To improve performance of large clusters, you can store Event objects in a separate
dedicated etcd instance.
When creating a cluster, you can (using custom tooling):
* start and configure additional etcd instance
* configure api-server to use it for storing events
* configure the {{< glossary_tooltip term_id="kube-apiserver" text="API server" >}} to use it for storing events
### Size of master and master components
## Addon resources
On GCE/Google Kubernetes Engine, and AWS, `kube-up` automatically configures the proper VM size for your master depending on the number of nodes
in your cluster. On other providers, you will need to configure it manually. For reference, the sizes we use on GCE are
Kubernetes [resource limits](/docs/concepts/configuration/manage-resources-containers/)
help to minimise the impact of memory leaks and other ways that pods and containers can
impact on other components. These resource limits can and should apply to
{{< glossary_tooltip text="addon" term_id="addons" >}} just as they apply to application
workloads.
* 1-5 nodes: n1-standard-1
* 6-10 nodes: n1-standard-2
* 11-100 nodes: n1-standard-4
* 101-250 nodes: n1-standard-8
* 251-500 nodes: n1-standard-16
* more than 500 nodes: n1-standard-32
And the sizes we use on AWS are
* 1-5 nodes: m3.medium
* 6-10 nodes: m3.large
* 11-100 nodes: m3.xlarge
* 101-250 nodes: m3.2xlarge
* 251-500 nodes: c4.4xlarge
* more than 500 nodes: c4.8xlarge
{{< note >}}
On Google Kubernetes Engine, the size of the master node adjusts automatically based on the size of your cluster. For more information, see [this blog post](https://cloudplatform.googleblog.com/2017/11/Cutting-Cluster-Management-Fees-on-Google-Kubernetes-Engine.html).
On AWS, master node sizes are currently set at cluster startup time and do not change, even if you later scale your cluster up or down by manually removing or adding nodes or using a cluster autoscaler.
{{< /note >}}
### Addon Resources
To prevent memory leaks or other resource issues in [cluster addons](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons) from consuming all the resources available on a node, Kubernetes sets resource limits on addon containers to limit the CPU and Memory resources they can consume (See PR [#10653](https://pr.k8s.io/10653/files) and [#10778](https://pr.k8s.io/10778/files)).
For example:
For example, you can set CPU and memory limits for a logging component:
```yaml
...
containers:
- name: fluentd-cloud-logging
image: k8s.gcr.io/fluentd-gcp:1.16
image: fluent/fluentd-kubernetes-daemonset:v1
resources:
limits:
cpu: 100m
memory: 200Mi
```
Except for Heapster, these limits are static and are based on data we collected from addons running on 4-node clusters (see [#10335](https://issue.k8s.io/10335#issuecomment-117861225)). The addons consume a lot more resources when running on large deployment clusters (see [#5880](http://issue.k8s.io/5880#issuecomment-113984085)). So, if a large cluster is deployed without adjusting these values, the addons may continuously get killed because they keep hitting the limits.
Addons' default limits are typically based on data collected from experience running
each addon on small or medium Kubernetes clusters. When running on large
clusters, addons often consume more of some resources than their default limits.
If a large cluster is deployed without adjusting these values, the addon(s)
may continuously get killed because they keep hitting the memory limit.
Alternatively, the addon may run but with poor performance due to CPU time
slice restrictions.
To avoid running into cluster addon resource issues, when creating a cluster with many nodes, consider the following:
To avoid running into cluster addon resource issues, when creating a cluster with
many nodes, consider the following:
* Scale memory and CPU limits for each of the following addons, if used, as you scale up the size of cluster (there is one replica of each handling the entire cluster so memory and CPU usage tends to grow proportionally with size/load on cluster):
* [InfluxDB and Grafana](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/cluster-monitoring/influxdb/influxdb-grafana-controller.yaml)
* [kubedns, dnsmasq, and sidecar](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/dns/kube-dns/kube-dns.yaml.in)
* [Kibana](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/fluentd-elasticsearch/kibana-deployment.yaml)
* Scale number of replicas for the following addons, if used, along with the size of cluster (there are multiple replicas of each so increasing replicas should help handle increased load, but, since load per replica also increases slightly, also consider increasing CPU/memory limits):
* [elasticsearch](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/fluentd-elasticsearch/es-statefulset.yaml)
* Increase memory and CPU limits slightly for each of the following addons, if used, along with the size of cluster (there is one replica per node but CPU/memory usage increases slightly along with cluster load/size as well):
* [FluentD with ElasticSearch Plugin](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/fluentd-elasticsearch/fluentd-es-ds.yaml)
* [FluentD with GCP Plugin](https://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/fluentd-gcp/fluentd-gcp-ds.yaml)
* Some addons scale vertically - there is one replica of the addon for the cluster
or serving a whole failure zone. For these addons, increase requests and limits
as you scale out your cluster.
* Many addons scale horizontally - you add capacity by running more pods - but with
a very large cluster you may also need to raise CPU or memory limits slightly.
The VerticalPodAutoscaler can run in _recommender_ mode to provide suggested
figures for requests and limits.
* Some addons run as one copy per node, controlled by a {{< glossary_tooltip text="DaemonSet"
term_id="daemonset" >}}: for example, a node-level log aggregator. Similar to
the case with horizontally-scaled addons, you may also need to raise CPU or memory
limits slightly.
Heapster's resource limits are set dynamically based on the initial size of your cluster (see [#16185](http://issue.k8s.io/16185)
and [#22940](http://issue.k8s.io/22940)). If you find that Heapster is running
out of resources, you should adjust the formulas that compute heapster memory request (see those PRs for details).
## {{% heading "whatsnext" %}}
For directions on how to detect if addon containers are hitting resource limits, see the
[Troubleshooting section of Compute Resources](/docs/concepts/configuration/manage-resources-containers/#troubleshooting).
### Allowing minor node failure at startup
For various reasons (see [#18969](https://github.com/kubernetes/kubernetes/issues/18969) for more details) running
`kube-up.sh` with a very large `NUM_NODES` may fail due to a very small number of nodes not coming up properly.
Currently you have two choices: restart the cluster (`kube-down.sh` and then `kube-up.sh` again), or before
running `kube-up.sh` set the environment variable `ALLOWED_NOTREADY_NODES` to whatever value you feel comfortable
with. This will allow `kube-up.sh` to succeed with fewer than `NUM_NODES` coming up. Depending on the
reason for the failure, those additional nodes may join later or the cluster may remain at a size of
`NUM_NODES - ALLOWED_NOTREADY_NODES`.
`VerticalPodAutoscaler` is a custom resource that you can deploy into your cluster
to help you manage resource requests and limits for pods.
Visit [Vertical Pod Autoscaler](https://github.com/kubernetes/autoscaler/tree/master/vertical-pod-autoscaler#readme)
to learn more about `VerticalPodAutoscaler` and how you can use it to scale cluster
components, including cluster-critical addons.
The [cluster autoscaler](https://github.com/kubernetes/autoscaler/tree/master/cluster-autoscaler#readme)
integrates with a number of cloud providers to help you run the right number of
nodes for the level of resource demand in your cluster.
+1 -1
View File
@@ -2441,7 +2441,7 @@ filename | sha512 hash
- AppProtocol is a new field on Service and Endpoints resources, enabled with the ServiceAppProtocol feature gate. ([#88503](https://github.com/kubernetes/kubernetes/pull/88503), [@robscott](https://github.com/robscott)) [SIG Apps and Network]
- BlockVolume and CSIBlockVolume features are now GA. ([#88673](https://github.com/kubernetes/kubernetes/pull/88673), [@jsafrane](https://github.com/jsafrane)) [SIG Apps, Node and Storage]
- Consumers of the 'certificatesigningrequests/approval' API must now grant permission to 'approve' CSRs for the 'signerName' specified on the CSR. More information on the new signerName field can be found at https://github.com/kubernetes/enhancements/blob/master/keps/sig-auth/20190607-certificates-api.md&#35;signers ([#88246](https://github.com/kubernetes/kubernetes/pull/88246), [@munnerz](https://github.com/munnerz)) [SIG API Machinery, Apps, Auth, CLI, Node and Testing]
- CustomResourceDefinition schemas that use `x-kubernetes-list-map-keys` to specify properties that uniquely identify list items must make those properties required or have a default value, to ensure those properties are present for all list items. See https://kubernetes.io/docs/reference/using-api/api-concepts/&#35;merge-strategy for details. ([#88076](https://github.com/kubernetes/kubernetes/pull/88076), [@eloyekunle](https://github.com/eloyekunle)) [SIG API Machinery and Testing]
- CustomResourceDefinition schemas that use `x-kubernetes-list-map-keys` to specify properties that uniquely identify list items must make those properties required or have a default value, to ensure those properties are present for all list items. See https://kubernetes.io/docs/reference/using-api/api-concepts/#merge-strategy for details. ([#88076](https://github.com/kubernetes/kubernetes/pull/88076), [@eloyekunle](https://github.com/eloyekunle)) [SIG API Machinery and Testing]
- Fixed missing validation of uniqueness of list items in lists with `x-kubernetes-list-type: map` or x-kubernetes-list-type: set` in CustomResources. ([#84920](https://github.com/kubernetes/kubernetes/pull/84920), [@sttts](https://github.com/sttts)) [SIG API Machinery]
- Fixes a regression with clients prior to 1.15 not being able to update podIP in pod status, or podCIDR in node spec, against >= 1.16 API servers ([#88505](https://github.com/kubernetes/kubernetes/pull/88505), [@liggitt](https://github.com/liggitt)) [SIG Apps and Network]
- Ingress: Add Exact and Prefix maching to Ingress PathTypes ([#88587](https://github.com/kubernetes/kubernetes/pull/88587), [@cmluciano](https://github.com/cmluciano)) [SIG Apps, Cluster Lifecycle and Network]
@@ -45,8 +45,8 @@ kubectl create namespace qos-example
For a Pod to be given a QoS class of Guaranteed:
* Every Container in the Pod must have a memory limit and a memory request, and they must be the same.
* Every Container in the Pod must have a CPU limit and a CPU request, and they must be the same.
* Every Container, including init containers, in the Pod must have a memory limit and a memory request, and they must be the same.
* Every Container, including init containers, in the Pod must have a CPU limit and a CPU request, and they must be the same.
Here is the configuration file for a Pod that has one Container. The Container has a memory limit and a
memory request, both equal to 200 MiB. The Container has a CPU limit and a CPU request, both equal to 700 milliCPU:
@@ -502,7 +502,14 @@ behavior:
selectPolicy: Disabled
```
## Implicit maintenance-mode deactivation
You can implicitly deactivate the HPA for a target without the
need to change the HPA configuration itself. If the target's desired replica count
is set to 0, and the HPA's minimum replica count is greater than 0, the HPA
stops adjusting the target (and sets the `ScalingActive` Condition on itself
to `false`) until you reactivate it by manually adjusting the target's desired
replica count or HPA's minimum replica count.
## {{% heading "whatsnext" %}}
@@ -26,7 +26,7 @@ Kubernetes concepts.
- [Pods](/docs/concepts/workloads/pods/)
- [Cluster DNS](/docs/concepts/services-networking/dns-pod-service/)
- [Headless Services](/docs/concepts/services-networking/service/#headless-services)
- [PersistentVolumes](/docs/concepts/storage/volumes/)
- [PersistentVolumes](/docs/concepts/storage/persistent-volumes/)
- [PersistentVolume Provisioning](https://github.com/kubernetes/examples/tree/{{< param "githubbranch" >}}/staging/persistent-volume-provisioning/)
- [StatefulSets](/docs/concepts/workloads/controllers/statefulset/)
- [PodDisruptionBudgets](/docs/concepts/workloads/pods/disruptions/#pod-disruption-budget)
@@ -522,7 +522,7 @@ log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L] - %m%n
```
This is the simplest possible way to safely log inside the container.
This is the simplest possible way to safely log inside the container.
Because the applications write logs to standard out, Kubernetes will handle log rotation for you.
Kubernetes also implements a sane retention policy that ensures application logs written to
standard out and standard error do not exhaust local storage media.