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update cloud controller manager docs for v1.8

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andrewsykim
2017-09-09 21:57:17 -04:00
committed by andrewsykim
parent b052e4e803
commit 6b70c56b25
4 changed files with 180 additions and 19 deletions
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_data/tasks.yml
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- docs/tasks/administer-cluster/limit-storage-consumption.md
- docs/tasks/administer-cluster/change-default-storage-class.md
- docs/tasks/administer-cluster/running-cloud-controller.md
- docs/tasks/administer-cluster/developing-cloud-controller-manager.md
- docs/tasks/administer-cluster/highly-available-master.md
- docs/tasks/administer-cluster/configure-multiple-schedulers.md
- docs/tasks/administer-cluster/ip-masq-agent.md
docs/tasks/administer-cluster/cloud-controller-manager-daemonset-example.yaml
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# This is an example of how to setup cloud-controller-manger as a Daemonset in your cluster.
# It assumes that your masters can run pods and has the role node-role.kubernetes.io/master
# Note that this Daemonset will not work straight out of the box for your cloud, this is
# meant to be a guideline.
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: cloud-controller-manager
namespace: kube-system
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
name: system:cloud-controller-manager
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: cluster-admin
subjects:
- kind: ServiceAccount
name: cloud-controller-manager
namespace: kube-system
---
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
labels:
k8s-app: cloud-controller-manager
name: cloud-controller-manager
namespace: kube-system
spec:
selector:
matchLabels:
k8s-app: cloud-controller-manager
template:
metadata:
labels:
k8s-app: cloud-controller-manager
spec:
serviceAccountName: cloud-controller-manager
containers:
- name: cloud-controller-manager
# for in-tree providers we use gcr.io/google_containers/cloud-controller-manager
# this can be replaced with any other image for out-of-tree providers
image: gcr.io/google_containers/cloud-controller-manager:v1.8.0
command:
- /usr/local/bin/cloud-controller-manager
- --cloud-provider=<YOUR_CLOUD_PROVIDER> # Add your own cloud provider here!
- --leader-elect=true
- --use-service-account-credentials
# these flags will vary for every cloud provider
- --allocate-node-cidrs=true
- --configure-cloud-routes=true
- --cluster-cidr=172.17.0.0/16
tolerations:
# this is required so CCM can bootstrap itself
- key: node.cloudprovider.kubernetes.io/uninitialized
value: "true"
effect: NoSchedule
# this is to have the daemonset runnable on master nodes
# the taint may vary depending on your cluster setup
- key: node-role.kubernetes.io/master
effect: NoSchedule
# this is to restrict CCM to only run on master nodes
# the node selector may vary depending on your cluster setup
nodeSelector:
node-role.kubernetes.io/master: ""
docs/tasks/administer-cluster/developing-cloud-controller-manager.md
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---
approvers:
- luxas
- thockin
- wlan0
title: Developing Cloud Controller Manager
---
**Cloud Controller Manager is an alpha feature in 1.8. In upcoming releases it will
be the preferred way to integrate Kubernetes with any cloud. This will ensure cloud providers
can develop their features independantly from the core Kubernetes release cycles.**
* TOC
{:toc}
## Background
Before going into how to build your own cloud controller manager, some background on how it works under the hood is helpful. The cloud controller manager is code from `kube-controller-manager` utilizing Go interfaces to allow implementations from any cloud to be plugged in. Most of the scaffolding and generic controller implementations will be in core, but it will always exec out to the cloud interfaces it is provided, so long as the [cloud provider interface](https://github.com/kubernetes/kubernetes/blob/master/pkg/cloudprovider/cloud.go#L29-L50) is satisifed.
To dive a little deeper into implementation details, all cloud controller managers will import packages from Kubernetes core, the only difference being each project will register their own cloud providers by calling [cloudprovider.RegisterCloudProvier](https://github.com/kubernetes/kubernetes/blob/master/pkg/cloudprovider/plugins.go#L42-L52) where a global variable of available cloud providers is updated.
## Developing
### Out of Tree
To build an out-of-tree cloud-controller-manager for your cloud, follow these steps:
1. Create a go package with an implementation that satisfies [cloudprovider.Interface](https://git.k8s.io/kubernetes/pkg/cloudprovider/cloud.go).
2. Use [main.go in cloud-controller-manager](https://github.com/kubernetes/kubernetes/blob/master/cmd/cloud-controller-manager/controller-manager.go) from Kubernestes core as a template for your main.go. As mentioned above, the only difference should be the cloud package that will be imported.
3. Import your cloud package in `main.go`, ensure your package has an `init` block to run [cloudprovider.RegisterCloudProvider](https://github.com/kubernetes/kubernetes/blob/master/pkg/cloudprovider/plugins.go#L42-L52).
Using existing out-of-tree cloud providers as an example may be helpful. You can find the list [here](/docs/tasks/administer-cluster/running-cloud-controller.md#examples).
### In Tree
For in-tree cloud providers, you can run the in-tree cloud controller manager as a [Daemonset](/docs/tasks/administer-cluster/cloud-controller-manager-daemonset-example.yaml) in your cluster. See the [running cloud controller manager docs](/docs/tasks/administer-cluster/running-cloud-controller.md) for more details.
docs/tasks/administer-cluster/running-cloud-controller.md
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@@ -1,38 +1,93 @@
---
approvers:
- luxas
- thockin
title: Build and Run cloud-controller-manager
- wlan0
title: Kubernetes Cloud Controller Manager
---
Kubernetes version 1.6 contains a new binary called as `cloud-controller-manager`. `cloud-controller-manager` is a daemon that embeds cloud-specific control loops in Kubernetes. These cloud-specific control loops were originally in the kube-controller-manager. However, cloud providers move at a different pace and schedule compared to the Kubernetes project, and abstracting the provider-specific code to the `cloud-controller-manager` binary allows cloud provider vendors to evolve independently from the core Kubernetes code.
The `cloud-controller-manager` can be linked to any cloud provider that satisifies the [cloudprovider.Interface](https://git.k8s.io/kubernetes/pkg/cloudprovider/cloud.go).
In future Kubernetes releases, cloud vendors should link code that satisfies the above interface to the `cloud-controller-manager` project and compile `cloud-controller-manager` for their own clouds. Cloud providers would also be responsible for maintaining and evolving their code.
**Cloud Controller Manager is an alpha feature in 1.8. In upcoming releases it will be the preferred way to integrate Kubernetes with any cloud. This will ensure cloud providers can develop their features independantly from the core Kubernetes release cycles.**
* TOC
{:toc}
### Building cloud-controller-manager for your cloud
## Cloud Controller Manager
To build cloud-controller-manager for your cloud, follow these steps:
Kubernetes v1.6 contains a new binary called `cloud-controller-manager`. `cloud-controller-manager` is a daemon that embeds cloud-specific control loops. These cloud-specific control loops were originally in the `kube-controller-manager`. Since cloud providers develop and release at a different pace compared to the Kubernetes project, abstracting the provider-specific code to the `cloud-controller-manager` binary allows cloud vendors to evolve independently from the core Kubernetes code.
1. Write a cloudprovider that satisfies the [cloudprovider.Interface](https://git.k8s.io/kubernetes/pkg/cloudprovider/cloud.go).
2. Link the cloudprovider to cloud-controller-manager.
The `cloud-controller-manager` can be linked to any cloud provider that satisifies [cloudprovider.Interface](https://git.k8s.io/kubernetes/pkg/cloudprovider/cloud.go). For backwards compatibility, the [cloud-controller-manager](https://github.com/kubernetes/kubernetes/tree/master/cmd/cloud-controller-manager) provided in the core Kubernetes project uses the same cloud libraries as `kube-controller-manager`. Cloud providers already supported in Kubernetes core are expected to use the in-tree cloud-controller-manager to transition out of Kubernetes core. In future Kubernetes releases, all cloud controller managers will be developed outside of the core Kubernetes project managed by sig leads or cloud vendors.
The methods in [cloudprovider.Interface](https://git.k8s.io/kubernetes/pkg/cloudprovider/cloud.go) are self-explanatory. All of the
[existing providers](https://git.k8s.io/kubernetes/pkg/cloudprovider/providers) satisfy this interface. If your cloud is already a part
of the existing providers, you do not need to write a new provider; you can proceed directly with linking your cloud provider to the `cloud-controller-manager`.
## Administration
Once your code is ready, you must import that code into `cloud-controller-manager`. See the [rancher cloud sample](https://github.com/rancher/rancher-cloud-controller-manager) for a reference example. The import step in the sample is the only step required to link your cloud provider to the `cloud-controller-manager`.
### Requirements
Every cloud has their own set of requirements for running their own cloud provider integration, it should not be too different from the requirements when running `kube-controller-manager`. As a general rule of thumb you'll need:
* cloud authentication/authorization: your cloud may require a token or IAM rules to allow access to their APIs
* kubernetes authentication/authorization: cloud-controller-manager may need RBAC rules set to speak to the kubernetes apiserver
* high availabilty: like kube-controller-manager, you may want a high available setup for cloud controller manager using leader election (on by default).
### Running cloud-controller-manager
To run `cloud-controller-manager`, add it to your existing Kubernetes cluster as a Master component. All other master components except `kube-controller-manager` can be run without any changes.
Successfully running cloud-controller-manager requires some changes to your cluster configuration.
The `kube-controller-manager` should not run any cloud-specific controllers, since the `cloud-controller-manager` takes over this responsibility. To prevent the `kube-controller-manager` from running cloud-specific controllers, you must set the `--cloud-provider` flag in `kube-controller-manager` to `external`.
The `kube-apiserver` should not run the Persistent Volume Label admission controller either since the `cloud-controller-manager` takes over labeling persistent volumes. To prevent the Persistent Volume Label admission plugin from running, make sure the `kube-apiserver` has a `--admission-control` flag with a value that does not include `PersistentVolumeLabel`.
For the `cloud-controller-manager` to label persistent volumes, initializers will need to be enabled and an InitializerConifguration needs to be added to the system. Follow [these instructions](/docs/admin/extensible-admission-controllers.md#enable-initializers-alpha-feature) to enable initializers. Use the following YAML to create the InitializerConfiguration:
* `kube-apiserver` and `kube-controller-manager` MUST NOT specify the `--cloud-provider` flag. This ensures that it does not run any cloud specific loops that would be run by cloud controller manager. In the future, this flag will be deprecated and removed.
* `kubelet` must run with `--cloud-provider=external`. This is to ensure that the kubelet is aware that it must be initialized by the cloud controller manager before it is scheduled any work.
* `kube-apiserver` SHOULD NOT run the `PersistentVolumeLabel` admission controller since the cloud controller manager takes over labeling persistent volumes. To prevent the PersistentVolumeLabel admission plugin from running, make sure the `kube-apiserver` has a `--admission-control` flag with a value that does not include `PersistentVolumeLabel`.
* For the `cloud-controller-manager` to label persistent volumes, initializers will need to be enabled and an InitializerConifguration needs to be added to the system. Follow [these instructions](/docs/admin/extensible-admission-controllers.md#enable-initializers-alpha-feature) to enable initializers. Use the following YAML to create the InitializerConfiguration:
{% include code.html language="yaml" file="persistent-volume-label-initializer-config.yaml" ghlink="/docs/tasks/administer-cluster/persistent-volume-label-initializer-config.yaml" %}
Keep in mind that setting up your cluster to use cloud controller manager will change your cluster behaviour in a few ways:
* kubelets specifying `--cloud-provider=external` will add a taint `node.cloudprovider.kubernetes.io/uninitialized` with an effect `NoSchedule` during initialization. This marks the node as needing a second initialization from an external controller before it can be scheduled work. Note that in the event that cloud controller manager is not available, new nodes in the cluster will be left unscheduable. The taint is important since the scheduler may require cloud specific information about nodes such as it's region or type (high cpu, gpu, high memory, spot instance, etc).
* cloud information about nodes in the cluster will no longer be retrieved using local metadata, but instead all API calls to retreive node information will go through cloud controller manager. This may mean you can restrict access to your cloud API on the kubelets for better security. For larger clusters you may want to consider if cloud controller manager will hit rate limits since it is now responsible for almost all API calls to your cloud from within the cluster.
As of v1.8, cloud controller manager can implement:
* node controller - responsible for updating kubernetes nodes using cloud APIs and deleting kubernetes nodes that were deleted on your cloud.
* service controller - responsible for loadbalancers on your cloud against services of type LoadBalancer.
* route controller - responsible for setting up network routes on your cloud
* [PersistentVolumeLabel Admission Controller](/docs/admin/admission-controllers#persistentvolumelabel) - responsible for labeling persistent volumes on your cloud - ensure that the persistent volume label admission plugin is not enabled on your kube-apiserver.
* any other features you would like to implement if you are running an out-of-tree provider.
## Examples
If you are using a cloud that is currently supported in Kubernetes core and would like to adopt cloud controller manager, see the [cloud controller manager in kubernetes core](https://github.com/kubernetes/kubernetes/tree/master/cmd/cloud-controller-manager).
For cloud controller managers not in Kubernetes core, you can find the respective projects in repos maintained by cloud vendors or sig leads.
* [DigitalOcean](https://github.com/digitalocean/digitalocean-cloud-controller-manager)
* [keepalived](https://github.com/munnerz/keepalived-cloud-provider)
* [Rancher](https://github.com/rancher/rancher-cloud-controller-manager)
For providers already in Kubernetes core, you can run the in-tree cloud controller manager as a Daemonset in your cluster, use the following as a guideline:
{% include code.html language="yaml" file="cloud-controller-manager-daemonset-example.yaml" ghlink="/docs/tasks/administer-cluster/cloud-controller-manager-daemonset-example.yaml" %}
## Limitations
Running cloud controller manager comes with a few possible limitations. Although these limitations are being addressed in upcoming releases, it's important that you are aware of these limitations for production workloads.
### Support for Volumes
Cloud controller manager does not implement any of the volume controllers found in `kube-controller-manager` as the volume integrations also require coordination with kubelets. As we evolve CSI (container storage interface) and add stronger support for flex volume plugins, necessary support will be added to cloud controller manager so that clouds can fully integrate with volumes. Learn more about out-of-tree CSI volume plugins [here](https://github.com/kubernetes/features/issues/178).
### Scalability
In the previous architecture for cloud providers, we relied on kubelets using a local metadata service to retreive node information about itself. With this new architecture, we now fully rely on the cloud controller managers to retrieve information for all nodes. For very larger clusters, you should consider possible bottle necks such as resource requirements and API rate limiting.
### Chicken and Egg
The goal of the cloud controller manager project is to decouple development of cloud features from the core Kubernetes project. Unforunately, many aspects of the Kubernetes project has assumptions that cloud provider features are tightly integrated into the project. As a result, adopting this new architecture can create several situations where a request is being made for information from a cloud provider, but the cloud controller manager may not be able to return that information without the original request being complete.
A good example of this is the TLS bootstrapping feature in the Kubelet. Currently, TLS bootstraping assumes that the Kubelet has the ability to ask the cloud provider (or a local metadata service) for all its address types (private, public, etc) but cloud controller manager cannot set a node's address types without being initialzed in the first place which requires that the kubelet has TLS certificates to communicate with the apiserver.
As this initiative evolves, changes will be made to address these issues in upcoming releases.
## Developing your own Cloud Controller Manager
To build and develop your own cloud controller manager, read the [Developing Cloud Controller Manager](/docs/tasks/administer-cluster/developing-cloud-controller-manager.md) doc.