日期：2015年12月15日

Kubernetes笔记（5）—— kubernetes layout

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Node（也称之为minion）运行docker container，而master则负责调度管理这些container。

Master运行下列服务：

  1. API Server—nearly all the components on the master and nodes accomplish their respective tasks by making API calls. These are handled by the API Server running on the master.
  2. Etcd—Etcd is a service whose job is to keep and replicate the current configuration and run state of the cluster. It is implemented as a lightweight distributed key-value store and was developed inside the CoreOS project.
  3. Scheduler and Controller Manager—These processes schedule containers (actually, pods—but more on them later) onto target nodes. They also make sure that the correct numbers of these things are running at all times.

Node运行下列进程：

  1. Kubelet—A special background process (daemon that runs on each node whose job is to respond to commands from the master to create, destroy, and monitor the containers on that host.
  2. Proxy—This is a simple network proxy that’s used to separate the IP address of a target container from the name of the service it provides.
  3. cAdvisor (optional)—http://bit.ly/1izYGLi[Container Advisor (cAdvisor)] is a special daemon that collects, aggregates, processes, and exports information about running containers. This information includes information about resource isolation, historical usage, and key network statistics.

 

 

Kubernetes笔记（4）—— application VS service

A service is a process that:
1. is designed to do a small number of things (often just one).
2. has no user interface and is invoked solely via some kind of API.
An application, on the other hand, is pretty much the opposite of that. It has a user interface (even if it’s just a command line) and often performs lots of different tasks. It can also expose an API, but that’s just bonus points.

个人理解，service一般专注做一件事，没有用户界面，并且通过API与application交互。而application会有用户界面，并且通常可以运行很多任务。举个例子，web browser就是application，而web server即为service。

A Kubernetes cluster does not manage a fleet of applications. It manages a cluster of services.A service running in a container managed by Kubernetes is designed to do a very small number of discrete things.

If your services are small and of limited purpose, then they can more easily be scheduled and re-arranged as your load demands. Otherwise, the dependencies become too much to manage and either your scale or your stability suffers.

K8s即是用来管理service的。