【Kubernetes】Pod 的组成字段
环境
- kubernetes 1.20.2
- Spring Boot 2.5.0-M1
目标
查看 Pod 的组成字段，学习 pod 的 yaml 的定义方式。
组成字段
通过命令 kubectl explain pod 来查看 Pod 的组成字段。
[root@master pod]# kubectl explain pod
KIND: Pod
VERSION: v1
DESCRIPTION:
Pod is a collection of containers that can run on a host. This resource is
created by clients and scheduled onto hosts.
FIELDS:
apiVersion <string>
APIVersion defines the versioned schema of this representation of an
object. Servers should convert recognized schemas to the latest internal
value, and may reject unrecognized values. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
kind <string>
Kind is a string value representing the REST resource this object
represents. Servers may infer this from the endpoint the client submits
requests to. Cannot be updated. In CamelCase. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
metadata <Object>
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
spec <Object>
Specification of the desired behavior of the pod. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
status <Object>
Most recently observed status of the pod. This data may not be up to date.
Populated by the system. Read-only. More info:
https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
从上面可以看到 Pod 的版本是 v1，后续有五大类型的字段。
apiVersion
编写 yaml 格式文件的第一行，可以通过 expain 命令查看资源获得。
Kind
资源的类型，现在接触到了两种资源。一种是使用最多的 Pod，在搭建集群时，接触到了 Node，即集群节点。
metadata
通用型的字段，基本上大家都有的。
spec
针对每种类型的资源，都有不同的规范，这个字段的差异很大。
status
当前资源所处的状态，一般由 Kubernetes 来更新这些字段，而不是我们，只读。
查看 Pod 信息
根据前面的说明，下面来看一个完整的 Pod 状态。其中的细节字段可以不用关心，现在应该能认识五个最基础的字段。
Pod 的名称，容器的名称和镜像应该不陌生，对于容器的资源限制，也是我们之前设置的。
容器的状态相关的字段，如果对 Docker 比较熟悉，应该也可以看懂。
kubectl get -f pod.yaml -o yaml
apiVersion: v1
kind: Pod
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"pod-demo1","namespace":"default"},"spec":{"containers":[{"image":"jiangbo920827/spring-demo:actuator","name":"pod-demo1","ports":[{"containerPort":8080}],"resources":{"limits":{"cpu":"200m","memory":"200Mi"}}}]}}
creationTimestamp: "2021-01-28T13:29:10Z"
name: pod-demo1
namespace: default
resourceVersion: "93714"
uid: 050f84d5-2e5c-4896-bcb3-007767b82f17
spec:
containers:
- image: jiangbo920827/spring-demo:actuator
imagePullPolicy: IfNotPresent
name: pod-demo1
ports:
- containerPort: 8080
protocol: TCP
resources:
limits:
cpu: 200m
memory: 200Mi
requests:
cpu: 200m
memory: 200Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: default-token-slbq5
readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
nodeName: node1
preemptionPolicy: PreemptLowerPriority
priority: 0
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
tolerations:
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
tolerationSeconds: 300
- effect: NoExecute
key: node.kubernetes.io/unreachable
operator: Exists
tolerationSeconds: 300
volumes:
- name: default-token-slbq5
secret:
defaultMode: 420
secretName: default-token-slbq5
status:
conditions:
- lastProbeTime: null
lastTransitionTime: "2021-01-28T13:29:10Z"
status: "True"
type: Initialized
- lastProbeTime: null
lastTransitionTime: "2021-01-28T13:29:12Z"
status: "True"
type: Ready
- lastProbeTime: null
lastTransitionTime: "2021-01-28T13:29:12Z"
status: "True"
type: ContainersReady
- lastProbeTime: null
lastTransitionTime: "2021-01-28T13:29:10Z"
status: "True"
type: PodScheduled
containerStatuses:
- containerID: docker://5e264ac5bb2ed1fe8cee028d8fa05bc463b30c85ab2c7d2b53fb9aac6d7deab8
image: jiangbo920827/spring-demo:actuator
imageID: docker-pullable://jiangbo920827/spring-demo@sha256:fef2dd74c274e783e4cf2f270da15cadbc0766c8a0d24dad31dd0258e2eb4722
lastState: {}
name: pod-demo1
ready: true
restartCount: 0
started: true
state:
running:
startedAt: "2021-01-28T13:29:12Z"
hostIP: 192.168.56.102
phase: Running
podIP: 10.244.1.64
podIPs:
- ip: 10.244.1.64
qosClass: Guaranteed
startTime: "2021-01-28T13:29:10Z"
描述 Pod 状态
除了上面查看 Pod 状态的方式外，还有一种方式，该种方式对于人们来说更可读。
kubectl describe -f pod.yaml
Name: pod-demo1
Namespace: default
Priority: 0
Node: node1/192.168.56.102
Start Time: Thu, 28 Jan 2021 21:29:10 +0800
Labels: <none>
Annotations: <none>
Status: Running
IP: 10.244.1.64
IPs:
IP: 10.244.1.64
Containers:
pod-demo1:
Container ID: docker://5e264ac5bb2ed1fe8cee028d8fa05bc463b30c85ab2c7d2b53fb9aac6d7deab8
Image: jiangbo920827/spring-demo:actuator
Image ID: docker-pullable://jiangbo920827/spring-demo@sha256:fef2dd74c274e783e4cf2f270da15cadbc0766c8a0d24dad31dd0258e2eb4722
Port: 8080/TCP
Host Port: 0/TCP
State: Running
Started: Thu, 28 Jan 2021 21:29:12 +0800
Ready: True
Restart Count: 0
Limits:
cpu: 200m
memory: 200Mi
Requests:
cpu: 200m
memory: 200Mi
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-slbq5 (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
default-token-slbq5:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-slbq5
Optional: false
QoS Class: Guaranteed
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 38m default-scheduler Successfully assigned default/pod-demo1 to node1
Normal Pulled 38m kubelet Container image "jiangbo920827/spring-demo:actuator" already present on machine
Normal Created 38m kubelet Created container pod-demo1
Normal Started 38m kubelet Started container pod-demo1
总结
介绍了 Pod 的组成字段，以及查看 Pod 信息的两种方式。第一种更接近定义的方式，后一种可读性更好。
