docker+k8s基础篇三

[root@www .kube]# kubectl get pod myapp-5bc569c47d-jh6qk -o yaml （我们可以通过查看pods资源信息的时候加上-o yaml来查看pods资源的详细信息，而这些详细信息的展示方式也是我们接下来要使用的配置清单来创建pods资源的形式。
apiVersion: v1 api群组的名称和版本
在实际定义中我们会使用group（组名）/version（版本）来定义的，如果没有定义组名，默认是cron（核心组）
kind: Pod 资源类别
metadata: 元数据
creationTimestamp: "2019-06-23T03:39:45Z"
generateName: myapp-5bc569c47d-
labels:
pod-template-hash: 5bc569c47d
run: myapp
name: myapp-5bc569c47d-jh6qk
namespace: default
ownerReferences:
- apiVersion: apps/v1
blockOwnerDeletion: true
controller: true
kind: ReplicaSet
name: myapp-5bc569c47d
uid: 8b17b969-9568-11e9-9101-000c291028e5
resourceVersion: ""
selfLink: /api/v1/namespaces/default/pods/myapp-5bc569c47d-jh6qk
uid: 8b1c0e97-9568-11e9-9101-000c291028e5
spec: 规格，定义我们要创建的资源需要满足什么规范和特性（这个字段下的内容从定义之初就已经决定了pods资源启动之后的特性）
containers:
- image: ikubernetes/myapp:v1
imagePullPolicy: IfNotPresent
name: myapp
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: default-token-7bd8r
readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
priority: 0
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
tolerations: 容忍度（污点）
- 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-7bd8r
secret:
defaultMode: 420
secretName: default-token-7bd8r
status: 这个字段定义了pods资源在当前的状态，上面的spec定义初始状态，status则定义当前状态（只读），如果我们定义的spec状态和后面运行的status当前状态不统一，k8s会自动把当前状态向目标状态转移或靠拢，直到满足用户期望的状态。
conditions:
- lastProbeTime: null
lastTransitionTime: "2019-06-23T03:39:45Z"
message: '0/3 nodes are available: 3 node(s) had taints that the pod didn''t tolerate.'
reason: Unschedulable
status: "False"
type: PodScheduled
phase: Pending
qosClass: BestEffort
[root@www .kube]#

[root@www .kube]# kubectl api-versions
k8s将api的版本都以组的形式来划分，这样我们后面如果是对版本升级，只需要对组内的版本升级即可，避免全部版本都受到影响。而且分组之后还能在一个组里面定义多个版本，来实现多版本并存。
admissionregistration.k8s.io/v1beta1
apiextensions.k8s.io/v1beta1
apiregistration.k8s.io/v1
apiregistration.k8s.io/v1beta1
apps/v1
apps/v1beta1
apps/v1beta2
authentication.k8s.io/v1
authentication.k8s.io/v1beta1
authorization.k8s.io/v1
authorization.k8s.io/v1beta1
autoscaling/v1
autoscaling/v2beta1
autoscaling/v2beta2
在各组的版本之间还分为了稳定版本（v1），稳定版表示定义好的接口在后续不会再进行变化，万一有变化也是在已有的接口上来增加新的接口。
非稳定版本（beta），表示定义的接口还会进行变化。
batch/v1
batch/v1beta1
certificates.k8s.io/v1beta1
coordination.k8s.io/v1
coordination.k8s.io/v1beta1
events.k8s.io/v1beta1
extensions/v1beta1
networking.k8s.io/v1
networking.k8s.io/v1beta1
node.k8s.io/v1beta1
policy/v1beta1
rbac.authorization.k8s.io/v1
rbac.authorization.k8s.io/v1beta1
scheduling.k8s.io/v1
scheduling.k8s.io/v1beta1
storage.k8s.io/v1
storage.k8s.io/v1beta1
v1
[root@www .kube]#

[root@www kubeadm]# kubectl explain pods（通过explain参数加上资源类别就能看到该资源应该怎么定义）
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/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/api-conventions.md#types-kinds metadata <Object> 在相应的字段下面只要看到Object就可以知道该字段下面是要嵌套很多二级字段的，但是二级字段我们还是不知道怎么去定义。
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata spec <Object>
Specification of the desired behavior of the pod. More info:
https://git.k8s.io/community/contributors/devel/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/api-conventions.md#spec-and-status [root@www kubeadm]# kubectl explain pods.metadata 通过资源类别加上带有Object标记的字段，我们就可以看到一级字段下二级字段的内容有那些怎么去定义等
KIND: Pod
VERSION: v1 RESOURCE: metadata <Object> DESCRIPTION:
Standard object's metadata. More info:
https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata ObjectMeta is metadata that all persisted resources must have, which
includes all objects users must create. FIELDS:
annotations <map[string]string> 二级字段加上map标记代表是映射字段，其字段是有k=v数据组成的json数组
Annotations is an unstructured key value map stored with a resource that
may be set by external tools to store and retrieve arbitrary metadata. They
are not queryable and should be preserved when modifying objects. More
info: http://kubernetes.io/docs/user-guide/annotations clusterName <string>
The name of the cluster which the object belongs to. This is used to
distinguish resources with same name and namespace in different clusters.
This field is not set anywhere right now and apiserver is going to ignore
it if set in create or update request. creationTimestamp <string>
.........
ownerReferences <[]Object> 二级字段下面还可以嵌套三级字段，和上面方法一样[root@www kubeadm]# kubectl explain pods.metadata.ownerReferences，通过加上不同级别的字段名称来看下字段下的内容，而且前面的[]号代表对象列表 （如果字段后面加上了-required-就代表这个字段是必选字段）
........

[root@www TestYaml]# kubectl create -f pod-test.yaml 然后使用create参数-f去指定加载的yaml文件名
pod/pod-number created
[root@www TestYaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
pod-kk 1/1 Running 0 88s
pod-number 1/2 CrashLoopBackOff 4 5m59s可以看到pod-number已经被创建

[root@www TestYaml]# kubectl describe pods pod-number 通过describe参数来查看pods的详细信息
Name: pod-number
Namespace: default
Priority: 0
PriorityClassName: <none>
Node: www.kubernetes.node1.com/192.168.181.140 运行在哪个节点上
Start Time: Wed, 26 Jun 2019 21:05:36 +0800
Labels: app=myweb
tier=Not-outside
Annotations: <none>
Status: Running 可以看到名称叫myweb状态是运行中
IP: 10.244.1.19
Containers:
myweb:
Container ID: docker://4b213ff75852bf943adc4a4f35dfb41dd881ac10b051bd545ca00f8bdbcb9ab1
Image: ikubernetes/myapp:v1
Image ID: docker-pullable://ikubernetes/myapp@sha256:9c3dc30b5219788b2b8a4b065f548b922a34479577befb54b03330999d30d513
Port: <none>
Host Port: <none>
State: Running
Started: Wed, 26 Jun 2019 21:05:41 +0800
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-n5fjx (ro)
busybox:
Container ID: docker://e2b6b439439202e1887b3182b3155bb7e6798460be48c42edafda046ef907e8f
Image: busybox:latest
Image ID: docker-pullable://busybox@sha256:7a4d4ed96e15d6a3fe8bfedb88e95b153b93e230a96906910d57fc4a13210160
Port: <none>
Host Port: <none>
Command:
/bin/sh
-c
echo $(date) >> /usr/share/nginx/html/index.html; sleep 5
State: Waiting 因为我们第二个容器创建之后运行的命令是有问题的，所有状态也是显示不正常的
Reason: CrashLoopBackOff
Last State: Terminated
Reason: Completed
Exit Code: 0
Started: Wed, 26 Jun 2019 21:27:15 +0800
Finished: Wed, 26 Jun 2019 21:27:20 +0800
Ready: False
Restart Count: 8
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-n5fjx (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-n5fjx:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-n5fjx
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events: 在这个字段信息下，我们可以看到整个yaml格式创建pods的过程
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 26m default-scheduler Successfully assigned default/pod-number to www.kubernetes.node1.com
Normal Created 25m kubelet, www.kubernetes.node1.com Created container myweb
Normal Pulled 25m kubelet, www.kubernetes.node1.com Container image "ikubernetes/myapp:v1" already present on machine
Normal Started 25m kubelet, www.kubernetes.node1.com Started container myweb
Warning Failed 25m kubelet, www.kubernetes.node1.com Failed to pull image "busybox:latest": rpc error: code = Unknown desc = Error response from daemon: Get https://registry-1.docker.io/v2/library/busybox/manifests/latest: Get https://auth.docker.io/token?scope=repository%3Alibrary%2Fbusybox%3Apull&service=registry.docker.io: net/http: TLS handshake timeout
Warning Failed 25m (x2 over 25m) kubelet, www.kubernetes.node1.com Error: ErrImagePull
Warning Failed 25m kubelet, www.kubernetes.node1.com Failed to pull image "busybox:latest": rpc error: code = Unknown desc = Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: TLS handshake timeout
Warning Failed 24m (x2 over 25m) kubelet, www.kubernetes.node1.com Error: ImagePullBackOff
Normal BackOff 24m (x2 over 25m) kubelet, www.kubernetes.node1.com Back-off pulling image "busybox:latest"
Normal Started 24m (x2 over 24m) kubelet, www.kubernetes.node1.com Started container busybox
Normal Pulling 23m (x5 over 25m) kubelet, www.kubernetes.node1.com Pulling image "busybox:latest"
Normal Created 23m (x3 over 24m) kubelet, www.kubernetes.node1.com Created container busybox
Normal Pulled 15m (x7 over 24m) kubelet, www.kubernetes.node1.com Successfully pulled image "busybox:latest"
Warning BackOff 54s (x89 over 23m) kubelet, www.kubernetes.node1.com Back-off restarting failed container

[root@www TestYaml]# kubectl logs pod-number busybox 我们通过logs参数指定查看pods里面容器的日志
/bin/sh: can't create /usr/share/nginx/html/index.html: nonexistent directory 可以看到报错内容，方便我们去查询容器的错误
[root@www TestYaml]# curl 10.244.1.19 因为我们创建的myweb是正常运行，但是没有访问请求，我们自己访问下myweb制造访问请求
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
[root@www TestYaml]# kubectl logs pod-number myweb
10.244.0.0 - - [26/Jun/2019:13:41:35 +0000] "GET / HTTP/1.1" 200 65 "-" "curl/7.29.0" "-" 可以看到来自master在什么时间对myweb进行了访问

[root@www TestYaml]# kubectl exec --help 可以使用exec命令来操作
命令行格式
Usage:
kubectl exec POD [-c CONTAINER] -- COMMAND [args...] [options]
注意command前面的--是固定格式
[root@www TestYaml]# kubectl exec -it pod-number -c myweb -- /bin/sh
/ #
[root@www TestYaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
pod-kk 1/1 Running 0 45m
pod-number 1/2 ErrImagePull 12 49m

[root@www TestYaml]# kubectl delete -f pod-test.yaml 我们在删除pods资源的时候可以基于yaml文件定义的pods资源来删除，这样我们即使删除了pods，但是yaml文件还存在，想创建随时可以create下就能出来，无需每次都run，避免人为命令行run的时候导致的问题
pod "pod-kk" deleted
[root@www TestYaml]# kubectl get pods 而且在基于yaml文件删除的时候发现删除的pods不在会被自动创建了，也就是说pods不在受控制器管理了，想删除随时可以删除和创建
NAME READY STATUS RESTARTS AGE
pod-number 1/2 Running 13 50m

[root@www TestYaml]# kubectl explain pods.spec.containers.imagePullPolicy
KIND: Pod
VERSION: v1FIELD: imagePullPolicy <string>DESCRIPTION:
Image pull policy. One of Always, Never, IfNotPresent. Defaults to Always
if :latest tag is specified, or IfNotPresent otherwise. Cannot be updated.
More info:
https://kubernetes.io/docs/concepts/containers/images#updating-images
imagePullPolicy字段定义了三种镜像获取的方式，而且当对象一旦被创建之后，改字段是不被允许的。
Always：总是去仓库里面拖镜像，而且如果镜像标签是latest，就默认从仓库获取镜像；
Never：总是以使用本地镜像，本地没有也不会去仓库里面拖镜像；
IfNotPresent：当本地没有才去仓库拖镜像，除了latest之外，其它的都遵循IfNotPresent模式。

[root@www TestYaml]# kubectl explain pods.spec.containers.ports
如果是创建的对象后面需要暴露端号出去，可以一次暴露多个端口，而且每个暴露出去的端口还可以自定义名字，最后还指明暴露的端口是什么协议
当然我们还注意的是例如对象是nginx，默认是80端口，及时在此不指定暴露的端口，默认也是暴露服务默认的端口。
KIND: Pod
VERSION: v1RESOURCE: ports <[]Object>DESCRIPTION:
List of ports to expose from the container. Exposing a port here gives the
system additional information about the network connections a container
uses, but is primarily informational. Not specifying a port here DOES NOT
prevent that port from being exposed. Any port which is listening on the
default "0.0.0.0" address inside a container will be accessible from the
network. Cannot be updated. ContainerPort represents a network port in a single container.
那从实际的角度来说指定容器端口即可containerPort
FIELDS:
containerPort <integer> -required-
Number of port to expose on the pod's IP address. This must be a valid port
number, 0 < x < 65536. hostIP <string>
What host IP to bind the external port to. hostPort <integer>
Number of port to expose on the host. If specified, this must be a valid
port number, 0 < x < 65536. If HostNetwork is specified, this must match
ContainerPort. Most containers do not need this. name <string>
If specified, this must be an IANA_SVC_NAME and unique within the pod. Each
named port in a pod must have a unique name. Name for the port that can be
referred to by services. protocol <string>
Protocol for port. Must be UDP, TCP, or SCTP. Defaults to "TCP".
没有指定协议，默认是tcp的协议
案例：
spec:
containers:
- name: myweb1
image: ikubernetes/myapp:v2
ports:
- name: http
containerPort: 80 可以一次暴露多个端口
- name: https
containerPort: 443

[root@www TestYaml]# kubectl explain pods.spec.containers.args
args指默认向command（命令）传递参数
KIND: Pod
VERSION: v1FIELD: args <[]string>DESCRIPTION:
Arguments to the entrypoint. The docker image's CMD is used if this is not
provided. Variable references $(VAR_NAME) are expanded using the
container's environment. If a variable cannot be resolved, the reference in
the input string will be unchanged. The $(VAR_NAME) syntax can be escaped
with a double $$, ie: $$(VAR_NAME). Escaped references will never be
expanded, regardless of whether the variable exists or not. Cannot be
updated. More info:
https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell
[root@www TestYaml]# kubectl explain pods.spec.containers.command
command指向要运行的对象给与默认执行的命令或者程序
KIND: Pod
VERSION: v1FIELD: command <[]string>DESCRIPTION:
Entrypoint array. Not executed within a shell（默认给出的命令是不会运行在shell里面的，如果想运行在sehll里面需要自己指定 ）. The docker image's
ENTRYPOINT is used if this is not provided. Variable references $(VAR_NAME)
are expanded using the container's environment. If a variable cannot be
resolved, the reference in the input string will be unchanged. The
$(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME).
Escaped references will never be expanded, regardless of whether the
variable exists or not. Cannot be updated. More info:
https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell

[root@www TestYaml]# kubectl get pods --show-labels 通过参数--show-labels来查看对象标签
NAME READY STATUS RESTARTS AGE LABELS
pod-yy 1/1 Running 0 61m app=myweb1,tier=Not-outside
[root@www TestYaml]# kubectl get pods -L app 加-L参数值过滤查询对象标签的值
NAME READY STATUS RESTARTS AGE APP
pod-kk 1/1 Running 1 2m57s mypod01
pod-yy 1/1 Running 0 66m myweb1
[root@www TestYaml]# kubectl get pods -l app --show-labels -l过滤查看指包含app这个标签一类的对象
NAME READY STATUS RESTARTS AGE LABELS
pod-kk 1/1 Running 1 5m6s app=mypod01,tier=Not-outside
pod-yy 1/1 Running 0 68m app=myweb1,tier=Not-outside

Usage:
kubectl label [--overwrite] (-f FILENAME | TYPE NAME) KEY_1=VAL_1 ... KEY_N=VAL_N [--resource-version=version]
[options]
[root@www TestYaml]# kubectl label pods pod-kk edition=beta_version
pod/pod-kk labeled
[root@www TestYaml]# kubectl get pods pod-kk --show-labels 可以看到新的标签已经标记完成
NAME READY STATUS RESTARTS AGE LABELS
pod-kk 1/1 Running 1 11m app=mypod01,edition=beta_version,tier=Not-outside

k8s的标签选择器支持两种方式来进行选择性查询：
等值关系的标签选择器：
支持：=，==，!=
[root@www TestYaml]# kubectl get pods -l app=mypod01 --show-labels 等于
NAME READY STATUS RESTARTS AGE LABELS
pod-kk 1/1 Running 1 20m app=mypod01,edition=beta_version,tier=Not-outside
[root@www TestYaml]# kubectl get pods -l app!=mypod01 --show-labels 不等于
NAME READY STATUS RESTARTS AGE LABELS
pod-yy 1/1 Running 0 83m app=myweb1,tier=Not-outside
[root@www TestYaml]# kubectl get pods -l app=mypod01,edition=beta_version --show-labels 同时满足多个条件的
NAME READY STATUS RESTARTS AGE LABELS
pod-kk 1/1 Running 1 22m app=mypod01,edition=beta_version,tier=Not-outside
集合关系的标签选择器：
key in （value1，value2）
key notin （value1，value2）
key和!key
[root@www TestYaml]# kubectl get pods -l "edition in (beta_version)" --show-labels
NAME READY STATUS RESTARTS AGE LABELS
pod-kk 1/1 Running 1 37m app=mypod01,edition=beta_version,tier=Not-outside
[root@www TestYaml]#

[root@www TestYaml]# kubectl get nodes --show-labels
NAME STATUS ROLES AGE VERSION LABELS
beta.kubernetes.io是前缀，这个前缀是dns域名
www.kubernetes.master.com Ready master 142m v1.14.1 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=www.kubernetes.master.com,kubernetes.io/os=linux,node-role.kubernetes.io/master=
www.kubernetes.node1.com Ready <none> 140m v1.14.3 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=www.kubernetes.node1.com,kubernetes.io/os=linux
www.kubernetes.node2.com Ready <none> 140m v1.14.3 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=www.kubernetes.node2.com,kubernetes.io/os=linux
[root@www TestYaml]#

nodeSelector节点选择器，可以选择pod在哪个节点上运行，这样我们可以指定该pod在哪个或者哪类节点上运行，因为我们几点资源不都是一样的，有的可能是虚拟机和云机，有的是ibm或者dell的实体机等，针对这种我们做监控也得有针对性的运行pods
[root@www TestYaml]# kubectl explain pods.spec.nodeSelector
KIND: Pod
VERSION: v1FIELD: nodeSelector <map[string]string> 注意字段的类型DESCRIPTION:
NodeSelector is a selector which must be true for the pod to fit on a node.
Selector which must match a node's labels for the pod to be scheduled on
that node. More info:
https://kubernetes.io/docs/concepts/configuration/assign-pod-node/
spec:
containers:
- name: mypod01
image: ikubernetes/myapp:v2
ports:
- name: http
containerPort: 80
- name: https
containerPort: 443
nodeSelector: 例如我们定义改pods只能运行在带有IBM标签的机器上，当然得事先定义带IMB的标签
lable: IBM
如果不想这么麻烦，我就想直接指定节点，也可以，字段是nodeName
[root@www TestYaml]# kubectl explain pods.spec.nodeName
KIND: Pod
VERSION: v1FIELD: nodeName <string>DESCRIPTION:
NodeName is a request to schedule this pod onto a specific node. If it is
non-empty, the scheduler simply schedules this pod onto that node, assuming
that it fits resource requirements.

annotations:资源注解，这个label不同的是，不能作为标签选择器的挑选机制所存在，只能为对象提供元数据，而且资源描述是没有字符限制的。当创建的大型且重要对象的适合，资源描述尤为重要。
[root@www TestYaml]# cat pod-test.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-kk
namespace: default
labels:
app: mypod01
tier: Not-outside
annotations: 我们定义了三个资源的描述
creator: "Tommy"
create_time: "2019-06-30"
Contact_information: "baidu@163.com"
spec:
containers:
- name: mypod01
image: ikubernetes/myapp:v2
ports:
- name: http
containerPort: 80
- name: https
containerPort: 443
nodeSelector:
lable: IBM
[root@www TestYaml]# kubectl create -f pod-test.yaml
pod/pod-kk created
[root@www TestYaml]# kubectl describe pods pod-kk
Name: pod-kk
Namespace: default
Priority: 0
PriorityClassName: <none>
Node: <none>
Labels: app=mypod01
tier=Not-outside
Annotations: Contact_information: baidu@163.com 可以看到Annotations的信息，但是不是安装我们定义的顺序来的，但是无关紧要。
create_time: 2019-06-30
creator: Tommy
Status: Pending
IP:
Containers:
mypod01:
Image: ikubernetes/myapp:v2
Ports: 80/TCP, 443/TCP
Host Ports: 0/TCP, 0/TCP
Environment: <none>
..........

[root@www TestYaml]# kubectl explain pods.spec.restartPolicy
restartPolicy用来给重启容器，当探测到容器挂了，restartPolicy会提供三种选项给用户，Always（总是重启），OnFailure（只有正常终止的才重启），Never（从不重启）
KIND: Pod
VERSION: v1FIELD: restartPolicy <string>DESCRIPTION:
Restart policy for all containers within the pod. One of Always, OnFailure,
Never. Default to Always. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy

[root@www home]# kubectl explain pod.spec.containers.livenessProbe
KIND: Pod
VERSION: v1RESOURCE: livenessProbe <Object>DESCRIPTION:
Periodic probe of container liveness. Container will be restarted if the
probe fails. Cannot be updated. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes Probe describes a health check to be performed against a container to
determine whether it is alive or ready to receive traffic.FIELDS:
exec <Object> 第一种
One and only one of the following should be specified. Exec specifies the
action to take. failureThreshold <integer> 指定探测的多少次都是失败的，才认为是失败的
Minimum consecutive failures for the probe to be considered failed after
having succeeded. Defaults to 3（默认是3此）. Minimum value is 1.（最少是一次） httpGet <Object> 第二种
HTTPGet specifies the http request to perform. initialDelaySeconds <integer> 在docker容器在启动的时候立即做探测，这个时候可能主程序还没有启动完成，这个时候探测结果有可能是失败造成误伤，在多长时间之后进行探测
Number of seconds after the container has started before liveness probes 默认是容器一旦启动就立马探测
are initiated. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes periodSeconds <integer> 指定探测次数之后间隔多长时间来进行探测
How often (in seconds) to perform the probe. Default to 10 （默认是10秒探测一次）seconds. Minimum
value is 1. successThreshold <integer>
Minimum consecutive successes for the probe to be considered successful
after having failed. Defaults to 1. Must be 1 for liveness. Minimum value
is 1. tcpSocket <Object>第三种
TCPSocket specifies an action involving a TCP port. TCP hooks not yet
supported timeoutSeconds <integer> 指定探测间隔时间之后超时多长时间
Number of seconds after which the probe times out. Defaults to 1（默认是1秒） second.
Minimum value is 1. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
上面三种探针，我们一次创建指需要定义一个足以

[root@www home]# kubectl explain pod.spec.containers.readinessProbe
KIND: Pod
VERSION: v1RESOURCE: readinessProbe <Object> 探测方式和livenessProbe一样的，但是需要分清楚两者之间的属性，程序存活不代表程序就是就绪的DESCRIPTION:
Periodic probe of container service readiness. Container will be removed
from service endpoints if the probe fails. Cannot be updated. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes Probe describes a health check to be performed against a container to
determine whether it is alive or ready to receive traffic.FIELDS:
exec <Object>
One and only one of the following should be specified. Exec specifies the
action to take. failureThreshold <integer>
Minimum consecutive failures for the probe to be considered failed after
having succeeded. Defaults to 3. Minimum value is 1. httpGet <Object>
HTTPGet specifies the http request to perform. initialDelaySeconds <integer>
Number of seconds after the container has started before liveness probes
are initiated. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes periodSeconds <integer>
How often (in seconds) to perform the probe. Default to 10 seconds. Minimum
value is 1. successThreshold <integer>
Minimum consecutive successes for the probe to be considered successful
after having failed. Defaults to 1. Must be 1 for liveness. Minimum value
is 1. tcpSocket <Object>
TCPSocket specifies an action involving a TCP port. TCP hooks not yet
supported timeoutSeconds <integer>
Number of seconds after which the probe times out. Defaults to 1 second.
Minimum value is 1. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

[root@www home]# kubectl explain pod.spec.containers.lifecycle
这个什么周期是用来定义容器启动前和终止后的钩子参数的
KIND: Pod
VERSION: v1RESOURCE: lifecycle <Object>DESCRIPTION:
Actions that the management system should take in response to container
lifecycle events. Cannot be updated. Lifecycle describes actions that the management system should take in
response to container lifecycle events. For the PostStart and PreStop
lifecycle handlers, management of the container blocks until the action is
complete, unless the container process fails, in which case the handler is
aborted.FIELDS:
postStart <Object>
PostStart is called immediately after a container is created. If the
handler fails, the container is terminated and restarted according to its
restart policy. Other management of the container blocks until the hook
completes. More info:
https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks preStop <Object>
PreStop is called immediately before a container is terminated due to an
API request or management event such as liveness probe failure, preemption,
resource contention, etc. The handler is not called if the container
crashes or exits. The reason for termination is passed to the handler. The
Pod's termination grace period countdown begins before the PreStop hooked
is executed. Regardless of the outcome of the handler, the container will
eventually terminate within the Pod's termination grace period. Other
management of the container blocks until the hook completes or until the
termination grace period is reached. More info:
https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks
exec说明：

[root@www TestYaml]# kubectl explain pod.spec.containers.livenessProbe.exec
KIND: Pod
VERSION: v1RESOURCE: exec <Object>DESCRIPTION:
One and only one of the following should be specified. Exec specifies the
action to take. ExecAction describes a "run in container" action.FIELDS:要想使用exec命令必须是容器里面程序拥有并且能执行的命令才可以
command <[]string>
Command is the command line to execute inside the container, the working
directory for the command is root ('/') in the container's filesystem. The
command is simply exec'd, it is not run inside a shell, so traditional
shell instructions ('|', etc) won't work. To use a shell, you need to
explicitly call out to that shell. Exit status of 0 is treated as
live/healthy and non-zero is unhealthy.

[root@www TestYaml]# cat pod-test.yaml
apiVersion: v1
kind: Pod
metadata:
name: busybox-test
namespace: default
spec:
containers:
- name: busybox-test-pod
image: busybox:latest
command: ["bin/sh","-c","touch /home/busybox; sleep 20; mv /home/busybox /tmp/; sleep 1200"] 我们给定命令让对象启动为容器之后执行的命令
livenessProbe:
exec: 使用exec加上命令对这个容器运行之后创建的文件进行命令的探测
command: ["test","-e","/home/busybox"]
initialDelaySeconds: 3 在容器启动后3秒才开始探测
periodSeconds: 4 每隔4秒探测一次
[root@www TestYaml]# kubectl create -f pod-test.yaml
pod/busybox-test created
[root@www TestYaml]# kubectl get pods -w
NAME READY STATUS RESTARTS AGE
busybox-test 1/1 Running 0 46s 可以看到pods开始是running的
pod-kk 0/1 Pending 0 19m
[root@www TestYaml]# kubectl describe pods busybox-test
Name: busybox-test
Namespace: default
Priority: 0
PriorityClassName: <none>
Node: www.kubernetes.node1.com/192.168.181.140
Start Time: Mon, 01 Jul 2019 21:01:03 +0800
Labels: <none>
Annotations: <none>
Status: Running 容器状态是running和实际的状态相符
IP: 10.244.1.22
Containers:
busybox-test-pod:
Container ID: docker://dce312cf24767a597ee177cf65d83686d1cf0a12a638708eb2810e78a18ab0de
Image: busybox:latest
Image ID: docker-pullable://busybox@sha256:7a4d4ed96e15d6a3fe8bfedb88e95b153b93e230a96906910d57fc4a13210160
Port: <none>
Host Port: <none>
Command:
bin/sh
-c
touch /home/busybox; sleep 20; mv /home/busybox /tmp/; sleep 1200
State: Waiting
Reason: CrashLoopBackOff
Last State: Terminated 但是看到最近一次的状态是结束的
Reason: Error 原因是错误
Exit Code: 137 退出的代码是137
Started: Mon, 01 Jul 2019 21:19:55 +0800 启动的时间
Finished: Mon, 01 Jul 2019 21:20:57 +0800 完成的时间
Ready: False
Restart Count: 9 已经帮忙重启了9次
Liveness: exec [test -e /home/busybox] delay=3s timeout=1s period=4s #success=1 #failure=3 可以看到详细的探测过程
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-npzp7 (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-npzp7:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-npzp7
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 20m default-scheduler Successfully assigned default/busybox-test to www.kubernetes.node1.com
Normal Pulled 17m (x3 over 20m) kubelet, www.kubernetes.node1.com Successfully pulled image "busybox:latest"
Normal Created 17m (x3 over 20m) kubelet, www.kubernetes.node1.com Created container busybox-test-pod
Normal Started 17m (x3 over 20m) kubelet, www.kubernetes.node1.com Started container busybox-test-pod
Warning Unhealthy 17m (x9 over 19m) kubelet, www.kubernetes.node1.com Liveness probe failed:
Normal Killing 17m (x3 over 19m) kubelet, www.kubernetes.node1.com Container busybox-test-pod failed liveness probe, will be restarted
Normal Pulling 9m57s (x8 over 20m) kubelet, www.kubernetes.node1.com Pulling image "busybox:latest"
Warning BackOff 21s (x36 over 12m) kubelet, www.kubernetes.node1.com Back-off restarting failed container
[root@www TestYaml]# kubectl get pods -w
NAME READY STATUS RESTARTS AGE
busybox-test 0/1 ErrImagePull 9 26m
pod-kk 0/1 Pending 0 44m
busybox-test 1/1 Running 10 26m
可以看到RESTARTS的数字在变化，说明一直在帮忙重启，标记的重启次数。
[root@www TestYaml]# kubectl get pods -w
NAME READY STATUS RESTARTS AGE
busybox-test 0/1 ErrImagePull 9 26m
pod-kk 0/1 Pending 0 44m
busybox-test 1/1 Running 10 26m
busybox-test 0/1 ErrImagePull 10 27m
busybox-test 0/1 CrashLoopBackOff 10 27m
重启10次之后直接显示容器挂了

[root@www TestYaml]# kubectl explain pod.spec.containers.livenessProbe.tcpSocket
KIND: Pod
VERSION: v1RESOURCE: tcpSocket <Object>DESCRIPTION:
TCPSocket specifies an action involving a TCP port. TCP hooks not yet
supported TCPSocketAction describes an action based on opening a socketFIELDS:
host <string> 必须要指定主机地址
Optional: Host name to connect to, defaults to the pod IP. port <string> -required- 必须指定从服务的那个端口来进行探测
Number or name of the port to access on the container. Number must be in
the range 1 to 65535. Name must be an IANA_SVC_NAME.

httpGet探测
[root@www TestYaml]# kubectl explain pod.spec.containers.livenessProbe.httpGet 如果对象是一个http服务，你们可以直接使用httpGet来探测
KIND: Pod
VERSION: v1RESOURCE: httpGet <Object>DESCRIPTION:
HTTPGet specifies the http request to perform. HTTPGetAction describes an action based on HTTP Get requests.FIELDS:
host <string>
Host name to connect to, defaults to the pod IP. You probably want to set
"Host" in httpHeaders instead. httpHeaders <[]Object>
Custom headers to set in the request. HTTP allows repeated headers. path <string> 直接像执行地址和端口的url发起请求，如果返回码是200，301,302都是代表正常，其它代表错误
Path to access on the HTTP server. port <string> -required-
Name or number of the port to access on the container. Number must be in
the range 1 to 65535. Name must be an IANA_SVC_NAME.如果定义暴露的端口有指定名称，可以通过命令来访问也行 scheme <string>
Scheme to use for connecting to the host. Defaults to HTTP.

[root@www TestYaml]# cat http-test-pod.yaml
apiVersion: v1
kind: Pod
metadata:
name: http-test
namespace: default
spec:
containers:
- name: http-test-pod
image: ikubernetes/myapp:v1
ports:
- name: myhttp
containerPort: 80
livenessProbe:
httpGet:
port: myhttp
path: /index.html
initialDelaySeconds: 3
periodSeconds: 4
[root@www TestYaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
busybox-test 0/1 CrashLoopBackOff 13 43m
http-test 1/1 Running 0 12s
pod-kk 0/1 Pending 0 61m
[root@www TestYaml]# kubectl describe pods http-test
Name: http-test
Namespace: default
Priority: 0
PriorityClassName: <none>
Node: www.kubernetes.node2.com/192.168.181.146
Start Time: Mon, 01 Jul 2019 21:44:04 +0800
Labels: <none>
Annotations: <none>
Status: Running
IP: 10.244.2.6
Containers:
http-test-pod:
Container ID: docker://67693dafae6c8b5f84bd344df045dbab0d5600fac67f42bfe00d06f1bfbc8b63
Image: ikubernetes/myapp:v1
Image ID: docker-pullable://ikubernetes/myapp@sha256:9c3dc30b5219788b2b8a4b065f548b922a34479577befb54b03330999d30d513
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Mon, 01 Jul 2019 21:44:09 +0800
Ready: True
Restart Count: 0
Liveness: http-get http://:myhttp/index.html delay=3s timeout=1s period=4s #success=1 #failure=3 可以看到整个探测的方式和详细的参数和参数值
是通过httpget的形式不断去的访问index.html这个url
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-npzp7 (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
default-token-npzp7:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-npzp7
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 81s default-scheduler Successfully assigned default/http-test to www.kubernetes.node2.com
Normal Pulled 77s kubelet, www.kubernetes.node2.com Container image "ikubernetes/myapp:v1" already present on machine
Normal Created 77s kubelet, www.kubernetes.node2.com Created container http-test-pod
Normal Started 76s kubelet, www.kubernetes.node2.com Started container http-test-pod
我们手动进入容器把index.html文件改名字然后在查看
[root@www TestYaml]# kubectl exec -it http-test -- /bin/sh
/ # cd /usr/share/nginx/html/
/usr/share/nginx/html # ls
50x.html index.html
/usr/share/nginx/html # mv index.html index.html.bak
/usr/share/nginx/html # ls
50x.html index.html.bak
/usr/share/nginx/html #
[root@www TestYaml]# kubectl describe pods http-test
Name: http-test
Namespace: default
Priority: 0
PriorityClassName: <none>
Node: www.kubernetes.node2.com/192.168.181.146
Start Time: Mon, 01 Jul 2019 21:44:04 +0800
Labels: <none>
Annotations: <none>
Status: Running
IP: 10.244.2.6
Containers:
http-test-pod:
Container ID: docker://850776a64342adae194fa117c6d53ca8baf1a672b33346169de8d687a16fd729
Image: ikubernetes/myapp:v1
Image ID: docker-pullable://ikubernetes/myapp@sha256:9c3dc30b5219788b2b8a4b065f548b922a34479577befb54b03330999d30d513
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Mon, 01 Jul 2019 21:49:41 +0800
Last State: Terminated
Reason: Completed
Exit Code: 0
Started: Mon, 01 Jul 2019 21:44:09 +0800
Finished: Mon, 01 Jul 2019 21:49:40 +0800
Ready: True
Restart Count: 1 可以看到已经在帮忙重启了一次
Liveness: http-get http://:myhttp/index.html delay=3s timeout=1s period=4s #success=1 #failure=3
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-npzp7 (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
default-token-npzp7:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-npzp7
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 6m3s default-scheduler Successfully assigned default/http-test to www.kubernetes.node2.com
Warning Unhealthy 27s (x3 over 35s) kubelet, www.kubernetes.node2.com Liveness probe failed: HTTP probe failed with statuscode: 404
Normal Killing 27s kubelet, www.kubernetes.node2.com Container http-test-pod failed liveness probe, will be restarted
Normal Pulled 26s (x2 over 5m59s) kubelet, www.kubernetes.node2.com Container image "ikubernetes/myapp:v1" already present on machine
Normal Created 26s (x2 over 5m59s) kubelet, www.kubernetes.node2.com Created container http-test-pod
Normal Started 26s (x2 over 5m58s) kubelet, www.kubernetes.node2.com Started container http-test-pod
[root@www TestYaml]# kubectl exec -it http-test -- /bin/sh
/ # cd /usr/share/nginx/html/
/usr/share/nginx/html # ls
50x.html index.html
/usr/share/nginx/html #
因为我们创建的容器在重启整个环境会被重置，重置之后index.html文件又因为环境的重置恢复了
[root@www TestYaml]# kubectl exec -it http-test -- /bin/sh
........
Last State: Terminated
Reason: Completed
Exit Code: 0
Started: Mon, 01 Jul 2019 21:44:09 +0800
Finished: Mon, 01 Jul 2019 21:49:40 +0800
Ready: True
Restart Count: 1
Liveness: http-get http://:myhttp/index.html delay=3s timeout=1s period=4s #success=1 #failure=3
Environment: <none>
[root@www TestYaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
busybox-test 0/1 CrashLoopBackOff 15 53m
http-test 1/1 Running 1 10m 可以看到重启的次数为1次
pod-kk 0/1 Pending 0 71m
[root@www TestYaml]# kubectl logs http-test http-test-pod
10.244.2.1 - - [01/Jul/2019:13:49:44 +0000] "GET /index.html HTTP/1.1" 200 65 "-" "kube-probe/1.14" "-"
10.244.2.1 - - [01/Jul/2019:13:49:48 +0000] "GET /index.html HTTP/1.1" 200 65 "-" "kube-probe/1.14" "-"
10.244.2.1 - - [01/Jul/2019:13:49:52 +0000] "GET /index.html HTTP/1.1" 200 65 "-" "kube-probe/1.14" "-"
......
[root@www TestYaml]# kubectl logs http-test http-test-pod | wc -l
110 已经探测了110次了
[root@www TestYaml]# kubectl logs http-test http-test-pod 我们再删除一次index.html，可以看到日志也提示了index.html文件不存在
2019/07/01 13:58:24 [error] 6#6: *131 open() "/usr/share/nginx/html/index.html" failed (2: No such file or directory), client: 10.244.2.1, server: localhost, request: "GET /index.html HTTP/1.1", host: "10.244.2.6:80"
10.244.2.1 - - [01/Jul/2019:13:58:24 +0000] "GET /index.html HTTP/1.1" 404 169 "-" "kube-probe/1.14" "-"
.....
重启之后又立马恢复正常

[root@www TestYaml]# cat readiness.http-get.yaml
apiVersion: v1
kind: Pod
metadata:
name: readiness-http-test
namespace: default
spec:
containers:
- name: readiness-http-test-pod
image: ikubernetes/myapp:v1
ports:
- name: http
containerPort: 80
readinessProbe:
httpGet:
port: http
path: /index.html
initialDelaySeconds: 3
periodSeconds: 4[root@www TestYaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
readiness-http-test 1/1 Running 0 12s
[root@www TestYaml]# kubectl exec -it readiness-http-test -- /bin/sh
/ # cd /usr/share/nginx/html/
/usr/share/nginx/html # rm -rf index.html 删掉主页文件
/usr/share/nginx/html # ls
50x.html
/usr/share/nginx/html #
[root@www ~]# kubectl get pods -w
NAME READY STATUS RESTARTS AGE
readiness-http-test 1/1 Running 0 119s
readiness-http-test 0/1 Running 0 2m38s 可以看到显示未就绪状态了/usr/share/nginx/html # netstat -anptu | grep 80 而此时我们的nginx还是运行的状态
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 1/nginx: master pro
tcp 0 0 10.244.1.23:80 10.244.1.1:37590 TIME_WAIT -
tcp 0 0 10.244.1.23:80 10.244.1.1:37586 TIME_WAIT -
/usr/share/nginx/html # touch index.html 我们手动touch一个index文件
/usr/share/nginx/html # ls
50x.html index.html
/usr/share/nginx/html #[root@www ~]# kubectl get pods -w
NAME READY STATUS RESTARTS AGE
readiness-http-test 1/1 Running 0 119s
readiness-http-test 0/1 Running 0 2m38s
readiness-http-test 1/1 Running 0 6m2s 可以看到又变成就绪的状态了

[root@www TestYaml]# kubectl explain pods.spec.containers.lifecycle
KIND: Pod
VERSION: v1RESOURCE: lifecycle <Object>DESCRIPTION:
Actions that the management system should take in response to container
lifecycle events. Cannot be updated. Lifecycle describes actions that the management system should take in
response to container lifecycle events. For the PostStart and PreStop
lifecycle handlers, management of the container blocks until the action is
complete, unless the container process fails, in which case the handler is
aborted.FIELDS:
postStart <Object> 支持启动后
PostStart is called immediately after a container is created. If the
handler fails, the container is terminated and restarted according to its
restart policy. Other management of the container blocks until the hook
completes. More info:
https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks preStop <Object>终止前
PreStop is called immediately before a container is terminated due to an
API request or management event such as liveness probe failure, preemption,
resource contention, etc. The handler is not called if the container
crashes or exits. The reason for termination is passed to the handler. The
Pod's termination grace period countdown begins before the PreStop hooked
is executed. Regardless of the outcome of the handler, the container will
eventually terminate within the Pod's termination grace period. Other
management of the container blocks until the hook completes or until the
termination grace period is reached. More info:
https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks
[root@www TestYaml]# kubectl explain pods.spec.containers.lifecycle.postStart
KIND: Pod
VERSION: v1RESOURCE: postStart <Object>DESCRIPTION:
PostStart is called immediately after a container is created. If the
handler fails, the container is terminated and restarted according to its
restart policy. Other management of the container blocks until the hook
completes. More info:
https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks Handler defines a specific action that should be takenFIELDS:
exec <Object>
One and only one of the following should be specified. Exec specifies the
action to take. httpGet <Object>
HTTPGet specifies the http request to perform. tcpSocket <Object>
TCPSocket specifies an action involving a TCP port. TCP hooks not yet
supported[root@www TestYaml]#[root@www TestYaml]# kubectl explain pods.spec.containers.lifecycle.preStop
KIND: Pod
VERSION: v1RESOURCE: preStop <Object> 终止前DESCRIPTION:
PreStop is called immediately before a container is terminated due to an
API request or management event such as liveness probe failure, preemption,
resource contention, etc. The handler is not called if the container
crashes or exits. The reason for termination is passed to the handler. The
Pod's termination grace period countdown begins before the PreStop hooked
is executed. Regardless of the outcome of the handler, the container will
eventually terminate within the Pod's termination grace period. Other
management of the container blocks until the hook completes or until the
termination grace period is reached. More info:
https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks Handler defines a specific action that should be takenFIELDS:
exec <Object> 可以看到三种方式和上面的探针一样，其功能也类似
One and only one of the following should be specified. Exec specifies the
action to take. httpGet <Object>
HTTPGet specifies the http request to perform. tcpSocket <Object>
TCPSocket specifies an action involving a TCP port. TCP hooks not yet
supported