I am trying to create a cron job in openshift and having trouble doing this with oc so I am looking for alternatives.
I have already tried: "oc run cron --image={imagename} \ --dry-run=false"
This created another resource. There was no parameter to create a cron job
There's already a good answer on how the two platforms overlap. You mentioned there was no parameter to create a cronjob. You can do that with oc through the following (resource):
oc run pi --image=perl --schedule='*/1 * * * *' \
--restart=OnFailure --labels parent="cronjobpi" \
--command -- perl -Mbignum=bpi -wle 'print bpi(2000)'
Or you can do it through a yaml file like the following:
apiVersion: batch/v1beta1
kind: CronJob
metadata:
name: hello
spec:
schedule: "*/1 * * * *"
jobTemplate:
spec:
template:
spec:
containers:
- name: hello
image: busybox
args:
- /bin/sh
- -c
- date; echo Hello from the Kubernetes cluster
restartPolicy: OnFailure
And then run:
oc create -f cronjob.yaml -n default
oc stands for openshift client which is a wrapper created on top of kubectl. It is created to communicate with openshift api server.
It supports all operations that are provided by kubectl and others that are specific to OpenShift like operations on templates, builds, build and development config, image stream etc
Related
I'm new to Openshfit. We are using openshift deployments to deploy our multiple microservice (SpringBoot application). The deployment is done from docker image.
We have a situation that we need to stop one micro service alone from Midnight till morning 5 AM ( due to an external dependency ).
Could someone suggest a way to do this automatically?
I was able to run
oc scale deployment/sampleservice--replicas=0 manually to make number of pods as zero and scale up to 1 manually later.
I'm not sure how to run this command on specific time automatically. The CronJob in Openshift should be able to do this. But not sure how to configure cronjob to execute an OC command.
Any guidance will be of great help
Using a cronjob is a good option.
First, you'll need an image that has the oc command line client available. I'm sure there's a prebuilt one out there somewhere, but since this will be running with privileges in your OpenShift cluster you want something you trust, which probably means building it yourself. I used:
FROM quay.io/centos/centos:8
RUN curl -o /tmp/openshift-client.tar.gz \
https://mirror.openshift.com/pub/openshift-v4/clients/ocp/latest/openshift-client-linux.tar.gz; \
tar -C /bin -xf /tmp/openshift-client.tar.gz oc kubectl; \
rm -f /tmp/openshift-client.tar.gz
ENTRYPOINT ["/bin/oc"]
In order to handle authentication correctly, you'll need to create a ServiceAccount and then assign it appropriate privileges through a Role and a RoleBinding. I created a ServiceAccount named oc-client-sa:
apiVersion: v1
kind: ServiceAccount
metadata:
name: oc-client-sa
namespace: oc-client-example
A Role named oc-client-role that grants privileges to Pod and Deployment objects:
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: oc-client-role
namespace: oc-client-example
rules:
- verbs:
- get
- list
- create
- watch
- patch
apiGroups:
- ''
resources:
- pods
- verbs:
- get
- list
- create
- watch
- patch
apiGroups:
- 'apps'
resources:
- deployments
- deployments/scale
And a RoleBinding that connects the oc-client-sa ServiceAccount
to the oc-client-role Role:
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
name: oc-client-rolebinding
namespace: oc-client-example
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: oc-client-role
subjects:
- kind: ServiceAccount
name: oc-client-sa
With all this in place, we can write a CronJob like this that will
scale down a deployment at a specific time. Note that we're running
the jobs using the oc-client-sa ServiceAccount we created earlier:
apiVersion: batch/v1
kind: CronJob
metadata:
name: scale-web-down
namespace: oc-client-example
spec:
schedule: "00 00 * * *"
concurrencyPolicy: Forbid
jobTemplate:
spec:
template:
spec:
serviceAccountName: oc-client-sa
restartPolicy: Never
containers:
- image: docker.io/larsks/openshift-client
args:
- scale
- deployment/sampleservice
- --replicas=0
name: oc-scale-down
You would write a similar one to scale things back up at 5AM.
The oc client will automatically use the credentials provided to your pod by Kubernetes because of the serviceAccountName setting.
API
You can use the OC rest api client and write the simple python code which will scale down replicas. Pack this python into a docker image and run it as a cronjob inside the OC cluster.
Simple Curl
Run a simple curl inside the cronjob to scale up & down deployment at a certain time.
Here is a simple Curl to scale the deployment: https://docs.openshift.com/container-platform/3.7/rest_api/apis-apps/v1beta1.Deployment.html#Get-apis-apps-v1beta1-namespaces-namespace-deployments-name-scale
API documentation : https://docs.openshift.com/container-platform/3.7/rest_api/apis-apps/v1beta1.Deployment.html
CLI
If you don't want to run code as docker image in cronjob of K8s, you can also run the command, in that case, use the docker image inside cronjob, and fire the command
OC-cli : https://hub.docker.com/r/widerin/openshift-cli
Dont forget authentication is required in both cases either API or running a command inside the cronjob.
I created a CronJob resource in Kubernetes.
I want to check the logs to validate that my crons are run. But not able to find any way to do that. I have gone through the commands but looks like all are for pod resource type.
Also tried following
$ kubectl logs cronjob/<resource_name>
error: cannot get the logs from *v1beta1.CronJob: selector for *v1beta1.CronJob not implemented
Questions:
How to check logs of CronJob Resource type?
If I want this resource to be in specific namespace, how to implement that same?
You need to check the logs of the pods which are created by the cronjob. The pods will be in completed state but you can check logs.
# here you can get the pod_name from the stdout of the cmd `kubectl get pods`
$ kubectl logs -f -n default <pod_name>
For creating a cronjob in a namespace just add namespace in metadata section. The pods will created in that namespace.
apiVersion: batch/v1beta1
kind: CronJob
metadata:
name: hello
namespace: default
spec:
schedule: "*/1 * * * *"
jobTemplate:
spec:
template:
spec:
containers:
- name: hello
image: busybox
args:
- /bin/sh
- -c
- date; echo Hello from the Kubernetes cluster
restartPolicy: OnFailure
Ideally you should be sending the logs to a log aggregator system such as ELK or Splunk.
In case you create job from cronjob it works like this:
kubectl -n "namespace" logs jobs.batch/<resource_name> --tail 4
Is this a valid imperative command for creating job?
kubectl create job my-job --image=busybox
I see this in https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands. But the command is not working. I am getting error as bellow:
Error: unknown flag: --image
What is the correct imperative command for creating job?
Try this one
kubectl create cronjob my-job --schedule="0,15,30,45 * * * *" --image=busy-box
What you have should work, though it not recommended as an approach anymore. I would check what version of kubectl you have, and possibly upgrade it if you aren't using the latest.
That said, the more common approach these days is to write a YAML file containing the Job definition and then run kubectl apply -f myjob.yaml or similar. This file-driven approach allowed for more natural version control, editing, review, etc.
Using correct value for --restart field on "kubectl run" will result run command to create an deployment or job or cronjob
--restart='Always': The restart policy for this Pod. Legal values [Always, OnFailure, Never]. If set to 'Always'
a deployment is created, if set to 'OnFailure' a job is created, if set to 'Never', a regular pod is created. For the
latter two --replicas must be 1. Default 'Always', for CronJobs `Never`.
Use "kubectl run" for creating basic kubernetes job using imperatively command as below
master $ kubectl run nginx --image=nginx --restart=OnFailure --dry-run -o yaml > output.yaml
Above should result an "output.yaml" as below example, you can edit this yaml for advance configurations as needed and create job by "kubectl create -f output.yaml or if you just need basic job then remove --dry-run option from above command and you will get basic job created.
apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
labels:
run: nginx
name: nginx
spec:
template:
metadata:
creationTimestamp: null
labels:
run: nginx
spec:
containers:
- image: nginx
name: nginx
resources: {}
restartPolicy: OnFailure
status: {}
When I set the Cronjob Schedule as */1 * * * *,it would work.
When I set any number which is in 0-59 to the crontab minute,such as 30 * * * *,it would work as well.
However when I set the Cronjob Schedule as 30 11 * * *,it even doesn`t create a job at 11:30.
All the config is followed:
apiVersion: batch/v1beta1
kind: CronJob
metadata:
name: hello
spec:
schedule: "33 11 * * *"
jobTemplate:
spec:
template:
spec:
containers:
- name: hello-cronjob
image: busybox
command: ["bash","-c","date;echo Hello from the Kubernetes cluste"]
restartPolicy: OnFailure
This is probably because your cluster is running in a different timezone then the one used by you.
You can check what timezone will be set in a POD using:
kubectl run -i --tty busybox --image=busybox --restart=Never -- date.
As for your yaml it looks good, there is no need to change anything with the spec.schedule value.
A small hint that might be helpful to you which is checking the logs from Jobs.
When you create CronJob when it's scheduled it will spawn a Job, you can see them using kubectl get jobs.
$ kubectl get jobs
NAME DESIRED SUCCESSFUL AGE
hello-1552390680 1 1 7s
If you use the name of that job hello-1552390680 and set it as a variable you can check the logs from that job.
$ pods=$(kubectl get pods --selector=job-name=hello-1552390680 --output=jsonpath={.items..metadata.name})
You can later check logs:
$ kubectl logs $pods
Tue Mar 12 11:38:04 UTC 2019
Hello from the Kubernetes cluster
Try this once and test result
0 30 11 1/1 * ? *
http://www.cronmaker.com/
Did someone has an experience running scheduled job? Due to the guide, ScheduledJobs available since 1.4 with enabled runtime batch/v2alpha1
So I was ensured with kubectl api-versions command:
autoscaling/v1
batch/v1
batch/v2alpha1
extensions/v1beta1
storage.k8s.io/v1beta1
v1
But when I tried sample template below with command kubectl apply -f job.yaml
apiVersion: batch/v2alpha1
kind: ScheduledJob
metadata:
name: hello
spec:
schedule: 0/1 * * * ?
jobTemplate:
spec:
template:
spec:
containers:
- name: hello
image: busybox
args:
- /bin/sh
- -c
- date; echo Hello from the Kubernetes cluster
restartPolicy: OnFailure
I got error
error validating "job.yaml": error validating data: couldn't find type: v2alpha1.ScheduledJob; if you choose to ignore these errors, turn validation off with --validate=false
It's possible that feature still not implemented? Or I made some error during template creation?
Thank you in advance.
Okay, I think I resolved this issue. ScheduledJobs is currently in alpha state and Google Container Engine supports this feature only for clusters with additionally enabled APIs. I was able to create such cluster with command:
gcloud alpha container clusters create my-cluster --enable-kubernetes-alpha
As a result now I have limited 30 day cluster with full feature support. I can see scheduled jobs with kubectl get scheduledjobs as well as create new ones with templates.
You can find more info about alpha clusters here.