In 2013, docker was born. Since then, it has been out of control. Its development is in full swing. If it is not an operation, if it is not docker, it is really outdated.
The kubernetes (also known as k8s) that appeared in 2014 are even more popular. I think most people just heard about it, but they didn't really use it. That article will bring everyone to kubernetes today.
Why is kubernetes also called k8s? It is said that because the word kubernetes is too long, it is not easy to remember, and there are 8 letters between the first letter and the last letter, so it is abbreviated as k8s. Kubernetes translates into Chinese, meaning "steering hand".
The reason why this article mentioned docker is because the k8s are fired and benefit from docker. K8s is simply a system for implementing container cluster management for auto-deploying, extending, and managing containers. It was developed by Google and its prototype is Google's internal container management system, Borg.
After more than ten years of optimization and improvement, Borg's function and efficiency are self-evident. The purpose of the k8s project is to extract the most essential parts of Borg, so that current developers can apply it more simply and directly. K8s has been destined for its extraordinary path since its birth.
In the past few years, Openstack was very hot, but in the past two years, k8s will overwrite Openstack. Although k8s can't completely replace Openstack, in the field of cloud computing, k8s is indeed a rising star. It can solve problems with container cloud and resolutely avoid traditional cloud.
In fact, the container management tool similar to the k8s function also has a Swarm. It is officially developed by docker. It is reasonable to say that the official docker thing should not be popularized by everyone. In fact, the experience of k8s is better than the official Swarm. The root cause is Still Borg.
To understand K8s better, you need to understand a few related concepts.
Node A physical machine, or a virtual machine (KVM type, not a container type); it is a historical reason to use a virtual machine as a node, or to completely isolate security issues.
Cluster A group of nodes needs to be centrally managed and called a cluster. A cluster has a master and multiple nodes. There is a kubelet in each node to obey the master to schedule and manage the node itself.
App containers A node can have one or more containerized applications, namely app containers. It can be thought of simply as a docker container.
Pod multiple app containers may need to share a hard disk, or share the same ip, so a group of app containers together called a pod. Typical applications are: one container keeps generating logs to the local hard disk, and the other container does not stop reading the local hard disk and uploading logs to the log server.
Service When a node hangs, the pods in the above pods and pods are naturally hanged. In order to die, you need to have an abstraction of the upper layer of the pod, the pod is hung up, and the service is still there. The service is exposed in the following ways.
ClusterIP (default), cluser's intranet ip, can only be seen in this cluster
NodePort, port NAT to outside of cluster
LoadBalancer, create an LB outside the cluster and assign a fixed IP visible outside to the LB
ExternalName, similar to CNAME mode
Deployment Configures the yaml format, which exists on the master. When the machine fails or needs to be horizontally scaled or needs to update the binary, the master does everything according to the configuration.
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