Pod of kubernetes

Kubernetes Of pod

pod yes k8s The smallest deployment unit of , The essence is sharing Network、IPC and UTS A collection of namespaces and containers that store resources ,pod Processes run in isolated containers , Each container shares network resources and storage resources , Every pod There is a root container pause,pod There are multiple containers in , Sharing networks and resources between containers ,pause Containers manage all containers .pod Multiple applications in are more convenient for interaction .

Network sharing

adopt pause Containers , Add other business containers to pause In the container , Let all business containers be in the same namespace Next , So as to realize network sharing .

Resource sharing

All resources are shared , Namely pod persist , At present pod After being removed , new pod You can also read the previous data , The principle is pod The data is stored in volume Data volume

Pull strategy

IfNotPresent： Pull when the image does not exist

Always： Each creation pod Pull the image when

Never： Never take the initiative to pull the image

Resource constraints

pod You can set resource limits , Do not schedule resources that do not meet the resource limit

Restart strategy

pod Of restartPolicy Policy configuration restart policy ,Always Indicates that the container always restarts when it terminates and exits , The default is automatic restart ,OnFailure It means that the container is restarted only when it exits abnormally ,Never Indicates no restart

health examination

pod You can perform health checks on the service , You can determine whether the service is healthy by accessing the service interface or establishing a connection with the service , Health detection strategies include survival checks livenessProbe And readiness check readinessProbe

The survival check is to kill the container if the check fails , Then operate according to the restart policy

The readiness check is if the check fails ,kubernetes Will be able to pod from service endpoints Remove

probe The probe supports three detection methods ：

1. httpget: send out http request , return 200-400 The status code within the range is success
2. exec： perform shell The command return status code is 0 That is success
3. tcpSocket： launch TCP Socket Connection established successfully

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