whentimeslows/website
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Resolving merge conflicts with master

Browse Source
This commit is contained in:
zacharysarah
2017-11-30 18:53:33 -06:00
parent 53f460ad9e a49d85186a
commit 538dd33ff2
5068 changed files with 25074 additions and 855452 deletions
Download Patch File Download Diff File Expand all files Collapse all files
docs/concepts/architecture/cloud-controller.md
+251
View File
@@ -0,0 +1,251 @@
---
title: Concepts Underlying the Cloud Controller Manager
---
## Cloud Controller Manager
The cloud controller manager (CCM) concept (not to be confused with the binary) was originally created to allow cloud specific vendor code and the Kubernetes core to evolve independent of one another. The cloud controller manager runs alongside other master components such as the Kubernetes controller manager, the API server, and scheduler. It can also be started as a Kubernetes addon, in which case, it runs on top of Kubernetes.
The cloud controller manager's design is based on a plugin mechanism that allows new cloud providers to integrate with Kubernetes easily by using plugins. There are plans in place for on-boarding new cloud providers on Kubernetes, and for migrating cloud provider from the old model to the new CCM model.
This document discusses the concepts behind the the cloud controller manager, and gives details about its associated functions.
Here's the architecture of a Kubernetes cluster without the cloud controller manager:
![Pre CCM Kube Arch](/images/docs/pre-ccm-arch.png)
## Design
In the preceding diagram, Kubernetes and the cloud provider are integrated through several different components:
* Kubelet
* Kubernetes controller manager
* Kubernetes API server
The CCM consolidates all of the cloud-dependent logic from the preceding three components to create a single point of integration with the cloud. The new architecture with the CCM looks like this:
![CCM Kube Arch](/images/docs/post-ccm-arch.png)
## Components of the CCM
The CCM breaks away some of the functionality of Kubernetes controller manager (KCM) and runs it as a separate process. Specifically, it breaks away those controllers in the KCM that are cloud dependent. The KCM has the following cloud dependent controller loops:
* Node controller
* Volume controller
* Route controller
* Service controller
In version 1.8, the CCM currently runs the following controllers from the preceding list:
* Node controller
* Route controller
* Service controller
Additionally, it runs another controller called the PersistentVolumeLabels controller. This controller is responsible for setting the zone and region labels on PersistentVolumes created in GCP and AWS clouds.
**Note:** Volume controller was deliberately chosen to not be a part of CCM. Due to the complexity involved and due to the existing efforts to abstract away vendor specific volume logic, it was decided that volume controller will not be moved to CCM.
{: .note}
The original plan to support volumes using CCM was to use Flex volumes to support pluggable volumes. However, a competing effort known as CSI is being planned to replace Flex.
Considering these dynamics, we decided to have an intermediate stop gap measure until CSI becomes ready.
Work is in progress by the cloud provider working group (wg-cloud-provider) to enable PersistentVolume support using CCM. See [kubernetes/kubernetes#52371](https://github.com/kubernetes/kubernetes/pull/52371).
## Functions of the CCM
The CCM inherits its functions from components of Kubernetes that are dependent on a cloud provider. This section is structured based on the components from which CCM inherits its functions.
### 1. Kubernetes controller manager
The majority of the CCM's functions are derived from the KCM. As mentioned in the previous section, the CCM runs the following control loops:
* Node controller
* Route controller
* Service controller
* PersistentVolumeLabels controller
#### Node controller
The Node controller is responsible for initializing a node by obtaining information about the nodes running in the cluster from the cloud provider. The node controller performs the following functions:
1. Initialize a node with cloud specific zone/region labels.
2. Initialize a node with cloud specific instance details, for example, type and size.
3. Obtain the node's network addresses and hostname.
4. In case a node becomes unresponsive, check the cloud to see if the node has been deleted from the cloud.
If the node has been deleted from the cloud, delete the Kubernetes Node object.
#### Route controller
The Route controller is responsible for configuring routes in the cloud appropriately so that containers on different nodes in the Kubernetes cluster can communicate with each other. The route controller is only applicable for Google Compute Engine clusters.
#### Service Controller
The Service controller is responsible for listening to service create, update, and delete events. Based on the current state of the services in Kubernetes, it configures cloud load balancers (such as ELB, or Google LB) to reflect the state of the services in Kubernetes. Additionally, it ensures that service backends for cloud load balancers are up to date.
#### PersistentVolumeLabels controller
The PersistentVolumeLabels controller applies labels on AWS EBS, GCE PD volumes when they are created. This removes the need for users to manually set the labels on these volumes.
These labels are essential for the scheduling of pods, as these volumes are constrained to work only within the region/zone that they are in, and therefore any Pod using these volumes needs to be scheduled in the same region/zone.
The PersistentVolumeLabels controller was created specifically for the CCM; that is, it did not exist before the CCM was created. This was done to move the PV labelling logic in the Kubernetes API server (it was an admission controller) to the CCM. It does not run on the KCM.
### 2. Kubelet
The Node controller contains the cloud-dependent functionality of the kubelet. Prior to the introduction of the CCM, the kubelet was responsible for initializing a node with cloud-specific details such as IP addresses, region/zone labels and instance type information. The introduction of the CCM has moved this initialization operation from the kubelet into the CCM.
In this new model, the kubelet initializes a node without cloud-specific information. However, it adds a taint to the newly created node that makes the node unschedulable until the CCM initializes the node with cloud-specific information, and then removes this taint.
### 3. Kubernets API server
The PersistentVolumeLabels controller moves the cloud-dependent functionality of the Kubernetes API server to the CCM as described in the preceding sections.
## Plugin mechanism
The cloud controller manager uses Go interfaces to allow implementations from any cloud to be plugged in. Specifically, it uses the CloudProvider Interface defined [here](https://github.com/kubernetes/kubernetes/blob/master/pkg/cloudprovider/cloud.go)
The implementation of the four shared controllers highlighted above, and some scaffolding along with the shared cloudprovider interface, will stay in the Kubernetes core, but implementations specific to cloud providers will
be built outside of the core, and implement interfaces defined in the core.
For more information about developing plugins, see
[Developing Cloud Controller Manager](/docs/tasks/administer-cluster/developing-cloud-controller-manager/).
## Authorization
This section breaks down the access required on various API objects by the CCM to perform its operations.
### Node Controller
The Node controller only works with Node objects. It requires full access to get, list, create, update, patch, watch, and delete Node objects.
v1/Node:
- Get
- List
- Create
- Update
- Patch
- Watch
### Route controller
The route controller listens to Node object creation and configures routes appropriately. It requires get access to Node objects.
v1/Node:
- Get
### Service controller
The service controller listens to Service object create, update and delete events and then configures endpoints for those Services appropriately.
To access Services, it requires list, and watch access. To update Services, it requires patch and update access.
To set up endpoints for the Services, it requires access to create, list, get, watch, and update.
v1/Service:
- List
- Get
- Watch
- Patch
- Update
### PersistentVolumeLabels controller
The PersistentVolumeLabels controller listens on PersistentVolume (PV) create events and then updates them. This controller requires access to list, watch, get and update PVs.
v1/PersistentVolume:
- Get
- List
- Watch
- Update
### Others
The implementation of the core of CCM requires access to create events, and to ensure secure operation, it requires access to create ServiceAccounts.
v1/Event:
- Create
- Patch
- Update
v1/ServiceAccount:
- Create
The RBAC ClusterRole for the CCM looks like this:
```yaml
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
name: cloud-controller-manager
rules:
- apiGroups:
- ""
resources:
- events
verbs:
- create
- patch
- update
- apiGroups:
- ""
resources:
- nodes
verbs:
- '*'
- apiGroups:
- ""
resources:
- nodes/status
verbs:
- patch
- apiGroups:
- ""
resources:
- services
verbs:
- list
- patch
- update
- watch
- apiGroups:
- ""
resources:
- serviceaccounts
verbs:
- create
- apiGroups:
- ""
resources:
- persistentvolumes
verbs:
- get
- list
- update
- watch
- apiGroups:
- ""
resources:
- endpoints
verbs:
- create
- get
- list
- watch
- update
```
## Vendor Implementations
The following cloud providers have implemented CCMs for their own clouds.
* [Digital Ocean]()
* [Oracle]()
* [Azure]()
* [GCE]()
* [AWS]()
## Cluster Administration
Complete instructions for configuring and running the CCM are provided
[here](/docs/tasks/administer-cluster/running-cloud-controller/#cloud-controller-manager).
docs/concepts/architecture/master-node-communication.md
+1 -1
View File
@@ -99,7 +99,7 @@ public networks.
### SSH Tunnels
[Google Container Engine](https://cloud.google.com/container-engine/docs/) uses
[Google Kubernetes Engine](https://cloud.google.com/kubernetes-engine/) uses
SSH tunnels to protect the Master -> Cluster communication paths. In this
configuration, the apiserver initiates an SSH tunnel to each node in the
cluster (connecting to the ssh server listening on port 22) and passes all
docs/concepts/architecture/nodes.md
+12 -12
View File
@@ -12,7 +12,7 @@ title: Nodes
A `node` is a worker machine in Kubernetes, previously known as a `minion`. A node
may be a VM or physical machine, depending on the cluster. Each node has
the services necessary to run [pods](/docs/user-guide/pods) and is managed by the master
the services necessary to run [pods](/docs/concepts/workloads/pods/pod/) and is managed by the master
components. The services on a node include Docker, kubelet and kube-proxy. See
[The Kubernetes Node](https://git.k8s.io/community/contributors/design-proposals/architecture/architecture.md#the-kubernetes-node) section in the
architecture design doc for more details.
@@ -21,11 +21,11 @@ architecture design doc for more details.
A node's status contains the following information:
* [Addresses](#Addresses)
* ~~[Phase](#Phase)~~ **deprecated**
* [Condition](#Condition)
* [Capacity](#Capacity)
* [Info](#Info)
* [Addresses](#addresses)
* ~~[Phase](#phase)~~ **deprecated**
* [Condition](#condition)
* [Capacity](#capacity)
* [Info](#info)
Each section is described in detail below.
@@ -64,7 +64,7 @@ The node condition is represented as a JSON object. For example, the following r
]
```
If the Status of the Ready condition is "Unknown" or "False" for longer than the `pod-eviction-timeout`, an argument is passed to the [kube-controller-manager](/docs/admin/kube-controller-manager) and all of the Pods on the node are scheduled for deletion by the Node Controller. The default eviction timeout duration is **five minutes**. In some cases when the node is unreachable, the apiserver is unable to communicate with the kubelet on it. The decision to delete the pods cannot be communicated to the kubelet until it re-establishes communication with the apiserver. In the meantime, the pods which are scheduled for deletion may continue to run on the partitioned node.
If the Status of the Ready condition is "Unknown" or "False" for longer than the `pod-eviction-timeout`, an argument is passed to the [kube-controller-manager](/docs/admin/kube-controller-manager/) and all of the Pods on the node are scheduled for deletion by the Node Controller. The default eviction timeout duration is **five minutes**. In some cases when the node is unreachable, the apiserver is unable to communicate with the kubelet on it. The decision to delete the pods cannot be communicated to the kubelet until it re-establishes communication with the apiserver. In the meantime, the pods which are scheduled for deletion may continue to run on the partitioned node.
In versions of Kubernetes prior to 1.5, the node controller would [force delete](/docs/concepts/workloads/pods/pod/#force-deletion-of-pods)
these unreachable pods from the apiserver. However, in 1.5 and higher, the node controller does not force delete pods until it is
@@ -74,14 +74,14 @@ permanently left a cluster, the cluster administrator may need to delete the nod
Kubernetes causes all the Pod objects running on it to be deleted from the apiserver, freeing up their names.
Version 1.8 introduces an alpha feature that automatically creates
[taints](/docs/concepts/configuration/taint-and-toleration) that represent conditions.
[taints](/docs/concepts/configuration/taint-and-toleration/) that represent conditions.
To enable this behavior, pass an additional feature gate flag `--feature-gates=...,TaintNodesByCondition=true`
to the API server, controller manager, and scheduler.
When `TaintNodesByCondition` is enabled, the scheduler ignores conditions when considering a Node; instead
it looks at the Node's taints and a Pod's tolerations.
Now users can choose between the old scheduling model and a new, more flexible scheduling model.
A Pod that does not have any tolerations gets scheduled according to the old model. But a Pod that
A Pod that does not have any tolerations gets scheduled according to the old model. But a Pod that
tolerates the taints of a particular Node can be scheduled on that Node.
Note that because of small delay, usually less than one second, between time when condition is observed and a taint
@@ -101,7 +101,7 @@ The information is gathered by Kubelet from the node.
## Management
Unlike [pods](/docs/user-guide/pods) and [services](/docs/user-guide/services),
Unlike [pods](/docs/concepts/workloads/pods/pod/) and [services](/docs/concepts/workloads/pods/pod/),
a node is not inherently created by Kubernetes: it is created externally by cloud
providers like Google Compute Engine, or exists in your pool of physical or virtual
machines. What this means is that when Kubernetes creates a node, it is really
@@ -192,7 +192,7 @@ Starting in Kubernetes 1.6, the NodeController is also responsible for evicting
pods that are running on nodes with `NoExecute` taints, when the pods do not tolerate
the taints. Additionally, as an alpha feature that is disabled by default, the
NodeController is responsible for adding taints corresponding to node problems like
node unreachable or not ready. See [this documentation](/docs/concepts/configuration/taint-and-toleration)
node unreachable or not ready. See [this documentation](/docs/concepts/configuration/taint-and-toleration/)
for details about `NoExecute` taints and the alpha feature.
Starting in version 1.8, the node controller can be made responsible for creating taints that represent
@@ -209,7 +209,7 @@ For self-registration, the kubelet is started with the following options:
- `--cloud-provider` - How to talk to a cloud provider to read metadata about itself.
- `--register-node` - Automatically register with the API server.
- `--register-with-taints` - Register the node with the given list of taints (comma separated `<key>=<value>:<effect>`). No-op if `register-node` is false.
- `--node-ip` IP address of the node.
- `--node-ip` - IP address of the node.
- `--node-labels` - Labels to add when registering the node in the cluster.
- `--node-status-update-frequency` - Specifies how often kubelet posts node status to master.