上QQ阅读APP看书，第一时间看更新

Scaling Pods With ReplicaSets

Most applications should be scalable and all must be fault tolerant. Pods do not provide those features, ReplicaSets do.

We learned that Pods are the smallest unit in Kubernetes. We also learned that Pods are not fault tolerant. If a Pod is destroyed, Kubernetes will do nothing to remedy the problem. That is, if Pods are created without Controllers.

The first Controller we'll explore is called ReplicaSet. Its primary, and pretty much only function, is to ensure that a specified number of replicas of a Pod matches the actual state (almost) all the time. That means that ReplicaSets make Pods scalable.

We can think of ReplicaSets as a self-healing mechanism. As long as elementary conditions are met (for example, enough memory and CPU), Pods associated with a ReplicaSet are guaranteed to run. They provide fault-tolerance and high availability.

It is worth mentioning ReplicaSet is the next-generation ReplicationController. The only significant difference is that ReplicaSet has extended support for selectors. Everything else is the same. ReplicationController is considered deprecated, so we'll focus only on ReplicaSet.

ReplicaSet's primary function is to ensure that the specified number of replicas of a service are (almost) always running.

Let's explore ReplicaSet through examples and see how it works and what it does.

The first step is to create a Kubernetes cluster.

本周热推：

Kubernetes进阶实战 Unity 5.X从入门到精通小学生C++编程课堂（新手篇）Power BI数据分析：报表设计和数据可视化应用大全自动化测试实战宝典：Robot Framework+Python从小工到专家