Kubernetes(k8s)一次性任务:Job - 人生的哲理
source link: https://www.cnblogs.com/renshengdezheli/p/17450685.html
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一.系统环境
本文主要基于Kubernetes1.21.9和Linux操作系统CentOS7.4。
服务器版本 | docker软件版本 | Kubernetes(k8s)集群版本 | CPU架构 |
---|---|---|---|
CentOS Linux release 7.4.1708 (Core) | Docker version 20.10.12 | v1.21.9 | x86_64 |
Kubernetes集群架构:k8scloude1作为master节点,k8scloude2,k8scloude3作为worker节点。
服务器 | 操作系统版本 | CPU架构 | 进程 | 功能描述 |
---|---|---|---|---|
k8scloude1/192.168.110.130 | CentOS Linux release 7.4.1708 (Core) | x86_64 | docker,kube-apiserver,etcd,kube-scheduler,kube-controller-manager,kubelet,kube-proxy,coredns,calico | k8s master节点 |
k8scloude2/192.168.110.129 | CentOS Linux release 7.4.1708 (Core) | x86_64 | docker,kubelet,kube-proxy,calico | k8s worker节点 |
k8scloude3/192.168.110.128 | CentOS Linux release 7.4.1708 (Core) | x86_64 | docker,kubelet,kube-proxy,calico | k8s worker节点 |
Kubernetes是一个流行的容器编排平台,它为运行容器化应用程序提供了丰富的功能和工具。其中之一就是Kubernetes Job,它允许您在集群中运行一次性任务。
正常情况下,Kubernetes的工作负载控制器会尝试持续地将容器保持在运行状态,比如deployment,DaemonSet ,ReplicationController,ReplicaSet 。但有时候,您可能需要运行短暂的任务或批处理作业,这些任务只需要运行一次并完成特定的操作。这时,就可以使用Kubernetes Job来管理这些一次性任务。
使用job任务的前提是已经有一套可以正常运行的Kubernetes集群,关于Kubernetes(k8s)集群的安装部署,可以查看博客《Centos7 安装部署Kubernetes(k8s)集群》https://www.cnblogs.com/renshengdezheli/p/16686769.html。
三.Kubernetes Job简介
Kubernetes Job是一个控制器,它可以创建和管理一次性任务。当Job被创建时,它将自动创建一个或多个Pod来运行任务,直到任务成功完成为止。
与其他控制器不同,Job控制器负责确保Pod成功地完成任务后删除它们。这意味着如果任务失败或调度失败(例如,由于资源不足),Kubernetes将自动重新启动失败的Pod,直到任务成功完成为止。
四.创建一次性任务job
4.1 创建一个简单任务的job
创建job的yaml文件存放目录
[root@k8scloude1 ~]# mkdir jobandcronjob
[root@k8scloude1 ~]# cd jobandcronjob/
创建namespace
[root@k8scloude1 jobandcronjob]# kubectl create ns job
namespace/job created
切换namespace为job
[root@k8scloude1 jobandcronjob]# kubens job
Context "kubernetes-admin@kubernetes" modified.
Active namespace is "job".
查看job任务
[root@k8scloude1 jobandcronjob]# kubectl get job
No resources found in job namespace.
[root@k8scloude1 jobandcronjob]# kubectl get pod
No resources found in job namespace.
查看创建job的帮助
[root@k8scloude1 jobandcronjob]# kubectl create job --help
Create a job with the specified name.
Examples:
# Create a job
kubectl create job my-job --image=busybox
# Create a job with command
kubectl create job my-job --image=busybox -- date
# Create a job from a CronJob named "a-cronjob"
kubectl create job test-job --from=cronjob/a-cronjob
......
Usage:
kubectl create job NAME --image=image [--from=cronjob/name] -- [COMMAND] [args...] [options]
Use "kubectl options" for a list of global command-line options (applies to all commands).
生成创建job的yaml文件,注意:重启策略restartPolicy为Never,这表示如果容器退出,则Job将不会自动重启它。
yaml文件意思为:创建名为my-job的任务,它使用busybox镜像来创建一个容器,并将其用于执行任务。不过任务为空。
[root@k8scloude1 jobandcronjob]# kubectl create job my-job --image=busybox --dry-run=client -o yaml >myjob.yaml
[root@k8scloude1 jobandcronjob]# cat myjob.yaml
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
name: my-job
spec:
template:
metadata:
creationTimestamp: null
spec:
containers:
- image: busybox
name: my-job
resources: {}
restartPolicy: Never
status: {}
生成创建job的yaml文件,并执行命令"date -F ; sleep 10",一次性任务job就是date -F ; sleep 10输出当前时间并休眠10秒钟
[root@k8scloude1 jobandcronjob]# kubectl create job my-job --image=busybox --dry-run=client -o yaml -- sh -c "date ; sleep 10" >myjob.yaml
[root@k8scloude1 jobandcronjob]# cat myjob.yaml
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
name: my-job
spec:
template:
metadata:
creationTimestamp: null
spec:
containers:
- command:
- sh
- -c
- date ; sleep 10
image: busybox
name: my-job
resources: {}
#重启策略restartPolicy为Never,这表示如果容器退出,则Job将不会自动重启它。
restartPolicy: Never
status: {}
修改yaml文件并创建。
创建一个名为my-job的Job,并在其中定义一个容器,该容器将输出当前时间并休眠10秒钟。当my-job被创建时,Kubernetes将自动创建Pod来运行容器,并在容器成功完成任务后删除它们。
[root@k8scloude1 jobandcronjob]# vim myjob.yaml
[root@k8scloude1 jobandcronjob]# cat myjob.yaml
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
name: my-job
spec:
template:
metadata:
creationTimestamp: null
spec:
#terminationGracePeriodSeconds属性为0,这意味着当Pod被终止时,Kubernetes将立即杀死容器而不等待容器完成处理。这可以防止容器在超时之前卡住或处于锁定状态。
terminationGracePeriodSeconds: 0
containers:
- command:
- sh
- -c
- date ; sleep 10
image: busybox
#imagePullPolicy属性设置为IfNotPresent,这意味着如果本地没有缓存的镜像,则从远程拉取镜像。如果本地已经有了镜像,则直接使用本地镜像而不去远程拉取。
imagePullPolicy: IfNotPresent
name: my-job
resources: {}
#重启策略restartPolicy为Never,这表示如果容器退出,则Job将不会自动重启它。
restartPolicy: Never
status: {}
#生成job任务
[root@k8scloude1 jobandcronjob]# kubectl apply -f myjob.yaml
job.batch/my-job created
查看job任务,观察pod的状态。
可以发现my-job需要完成一次任务,任务完成之后,pod的状态变为Completed,job的COMPLETIONS变为1/1
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 0/1 6s 6s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-pgnf2 1/1 Running 0 8s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-pgnf2 0/1 Completed 0 11s
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 1/1 12s 2m17s
删除job任务
[root@k8scloude1 jobandcronjob]# kubectl delete job my-job
job.batch "my-job" deleted
4.2 创建需要执行多次的job任务
某些时候,任务需要确保被完成多次,才能确认任务被正常完成,这时候可以使用completions设置job的完成次数。
修改yaml文件。
有几个重要的参数要解释下:
- backoffLimit: 4 如果Job失败,则重试4次。
- completions: 6 Job结束需要成功运行的Pod个数,即状态为Completed的Pod数。在本例中,这意味着当有6个Pod完成任务后,Job将终止。
- parallelism: 2 一次性运行2个Pod,这意味着Kubernetes将同时启动2个Pod来并行执行任务。
如下yaml文件表示:创建一个名为my-job的Job对象,并在其中定义一个容器,该容器将输出当前时间并休眠10秒钟。当my-job被创建时,Kubernetes将自动创建2个Pod来运行容器,并在容器成功完成任务后删除它们。如果其中任何一个Pod失败,则Kubernetes将尝试重试该Pod,最多重试4次。在所有6个Pod成功运行并完成任务后,Job将终止。
[root@k8scloude1 jobandcronjob]# vim myjobparallelism.yaml
[root@k8scloude1 jobandcronjob]# cat myjobparallelism.yaml
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
name: my-job
spec:
#如果job失败,则重试4次
backoffLimit: 4
#job结束需要成功运行的Pod个数,即状态为Completed的pod数
completions: 6
#一次性运行2个pod
parallelism: 2
template:
metadata:
creationTimestamp: null
spec:
terminationGracePeriodSeconds: 0
containers:
- command:
- sh
- -c
- date ; sleep 10
image: busybox
imagePullPolicy: IfNotPresent
name: my-job
resources: {}
#restartPolicy属性为Never,这表示如果容器退出,则Job将不会自动重启它。
restartPolicy: Never
status: {}
创建job
[root@k8scloude1 jobandcronjob]# kubectl apply -f myjobparallelism.yaml
job.batch/my-job created
查看job及其pod状态,可以看到job完成了6次。
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 0/6 5s 5s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-dlrls 1/1 Running 0 7s
my-job-dwf4v 1/1 Running 0 7s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-6mtnm 1/1 Running 0 2s
my-job-dlrls 0/1 Completed 0 14s
my-job-dwf4v 0/1 Completed 0 14s
my-job-tvvz8 0/1 ContainerCreating 0 2s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-6mtnm 1/1 Running 0 9s
my-job-dlrls 0/1 Completed 0 21s
my-job-dwf4v 0/1 Completed 0 21s
my-job-tvvz8 1/1 Running 0 9s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-6mtnm 0/1 Completed 0 47s
my-job-dlrls 0/1 Completed 0 59s
my-job-dwf4v 0/1 Completed 0 59s
my-job-slkxf 0/1 Completed 0 35s
my-job-tvvz8 0/1 Completed 0 47s
my-job-zj5sx 0/1 Completed 0 36s
#此job完成了6次
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 6/6 35s 62s
删除job
[root@k8scloude1 jobandcronjob]# kubectl delete job my-job
job.batch "my-job" deleted
五.测试job失败重试次数
backoffLimit: 4 表示如果Job失败,则重试4次。我们要测试下job失败之后,是不是真的会重试4次。
修改yaml文件,这次故意执行错误的指令,sleep改为sleepx,查看重试次数。
job的重启策略:Nerver ,只要任务没有完成,就创建新pod运行,直到job完成 ,会产生多个pod; 只要job没有完成,就会重启pod,直到job完成。
[root@k8scloude1 jobandcronjob]# vim myjobparallelism.yaml
[root@k8scloude1 jobandcronjob]# cat myjobparallelism.yaml
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
name: my-job
spec:
#如果job失败,则重试4次
backoffLimit: 4
#job结束需要成功运行的Pod个数,即状态为Completed的pod数
completions: 6
#一次性运行2个pod
parallelism: 2
template:
metadata:
creationTimestamp: null
spec:
terminationGracePeriodSeconds: 0
containers:
- command:
- sh
- -c
- date ; sleepx 10
image: busybox
imagePullPolicy: IfNotPresent
name: my-job
resources: {}
restartPolicy: Never
status: {}
创建job
[root@k8scloude1 jobandcronjob]# kubectl apply -f myjobparallelism.yaml
job.batch/my-job created
查看job及其pod状态,可以看到生成了6个失败pod。
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 0/6 7s 7s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-52xln 0/1 Error 0 11s
my-job-kn6d5 0/1 Error 0 10s
my-job-plh2s 0/1 Error 0 11s
my-job-rrvwz 0/1 Error 0 9s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-52xln 0/1 Error 0 27s
my-job-9hqwn 0/1 Error 0 16s
my-job-kn6d5 0/1 Error 0 26s
my-job-n2rhz 0/1 Error 0 16s
my-job-plh2s 0/1 Error 0 27s
my-job-rrvwz 0/1 Error 0 25s
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 0/6 31s 31s
使用kubectl describe job
查看job的描述信息,发现job已经达到重试次数“Warning BackoffLimitExceeded 84s job-controller Job has reached the specified backoff limit”。
注意:backoffLimit重试的次数并不准,backoffLimit重试次数为4次,每次并行为2,所以应该是8次,但是只创建了6个pod就reached the specified backoff limit。
[root@k8scloude1 jobandcronjob]# kubectl describe job my-job
Name: my-job
Namespace: job
Selector: controller-uid=cbd4c4b9-d31d-420a-a3d7-c3e1680de96c
Labels: controller-uid=cbd4c4b9-d31d-420a-a3d7-c3e1680de96c
job-name=my-job
Annotations: <none>
Parallelism: 2
......
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 2m15s job-controller Created pod: my-job-plh2s
Normal SuccessfulCreate 2m15s job-controller Created pod: my-job-52xln
Normal SuccessfulCreate 2m14s job-controller Created pod: my-job-kn6d5
Normal SuccessfulCreate 2m13s job-controller Created pod: my-job-rrvwz
Normal SuccessfulCreate 2m4s job-controller Created pod: my-job-9hqwn
Normal SuccessfulCreate 2m4s job-controller Created pod: my-job-n2rhz
Warning BackoffLimitExceeded 84s job-controller Job has reached the specified backoff limit
删除job
[root@k8scloude1 jobandcronjob]# kubectl delete job my-job
job.batch "my-job" deleted
[root@k8scloude1 jobandcronjob]# kubectl get job
No resources found in job namespace.
六.job任务使用示例:计算圆周率
下面使用job任务计算圆周率。
本次用到perl语言,使用perl计算圆周率2000位。先提前拉取perl镜像。
先在worker节点下载perl镜像。
[root@k8scloude2 ~]# docker pull hub.c.163.com/library/perl:latest
[root@k8scloude3 ~]# docker pull hub.c.163.com/library/perl:latest
创建job任务,任务为perl -Mbignum=bpi -wle 'print bpi(2000)使用perl计算圆周率2000位
。
[root@k8scloude1 jobandcronjob]# cat myjobPI.yaml
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
name: my-job
spec:
template:
metadata:
creationTimestamp: null
spec:
terminationGracePeriodSeconds: 0
#"perl -Mbignum=bpi -wle 'print bpi(2000)'",表示容器将输出2000位精度的圆周率(π)值。
containers:
- command:
- sh
- -c
- perl -Mbignum=bpi -wle 'print bpi(2000)'
image: hub.c.163.com/library/perl
imagePullPolicy: IfNotPresent
name: my-job
resources: {}
restartPolicy: Never
status: {}
创建job
[root@k8scloude1 jobandcronjob]# kubectl apply -f myjobPI.yaml
job.batch/my-job created
查看job及其pod状态
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 0/1 4s 4s
[root@k8scloude1 jobandcronjob]# kubectl get pod
NAME READY STATUS RESTARTS AGE
my-job-m89bb 0/1 Completed 0 8s
[root@k8scloude1 jobandcronjob]# kubectl get job
NAME COMPLETIONS DURATION AGE
my-job 1/1 7s 12s
查看pod日志,可以看到PI的值,显示了PI 2000位的数值。
[root@k8scloude1 jobandcronjob]# kubectl logs my-job-m89bb
3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473035982534904287554687311595628638823537875937519577818577805321712268066130019278766111959092164201989380952572010654858632788659361533818279682303019520353018529689957736225994138912497217752834791315155748572424541506959508295331168617278558890750983817546374649393192550604009277016711390098488240128583616035637076601047101819429555961989467678374494482553797747268471040475346462080466842590694912933136770289891521047521620569660240580381501935112533824300355876402474964732639141992726042699227967823547816360093417216412199245863150302861829745557067498385054945885869269956909272107975093029553211653449872027559602364806654991198818347977535663698074265425278625518184175746728909777727938000816470600161452491921732172147723501414419735685481613611573525521334757418494684385233239073941433345477624168625189835694855620992192221842725502542568876717904946016534668049886272327917860857843838279679766814541009538837863609506800642251252051173929848960841284886269456042419652850222106611863067442786220391949450471237137869609563643719172874677646575739624138908658326459958133904780275898
删除job
[root@k8scloude1 jobandcronjob]# kubectl delete job my-job
job.batch "my-job" deleted
[root@k8scloude1 jobandcronjob]# kubectl get job
No resources found in job namespace.
PS:在某些情况下,我们可能希望将超时限制放在任务上,以避免长时间运行或卡死的情况。为此,Job支持一个activeDeadlineSeconds属性,该属性指定了任务的超时时间。如果任务超时,则Kubernetes将自动终止任务。
在本文中,我们介绍了Kubernetes Job的基本概念,使用方法,应用实例,包括如何创建和管理一次性任务,需要多次执行的job任务,使用job计算圆周率等。
通过使用Kubernetes Job,您可以轻松地管理一次性任务,从而使集群更加灵活、可靠和高效。
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