Move away from the webhook for driver/executor pod configurations

[liyinan926]

Given a number of occurrences of issues with the webhook that stops working after some time due to certificate issues, I'm thinking that the right direction in the long term is to move away from it. For anyone who's already on Spark 3.0, the pod template support for driver/executor pods may be the right way to go. The operator should be able to translate driver and executor configs in SparkApplications into driver and executor pod templates and use the templates when submitting applications. Creating this issue to track the work.

[suvashishtha]

@liyinan926 - Do you have an example somewhere how to use podtemplate in sparkapplication. would be really cool. thanks

[dszakallas]

Hi, I started working on this issue, and came up with a minimal working implementation in #1296

My approach is to put a template property in SparkPodSpec, and serialize its contents to a temporary file before the call to spark-submit, passing the file names in their respective spark.kubernetes.driver.podTemplateFile and spark.kubernetes.executor.podTemplateFile conf options. The files can be cleaned up immediately after spark-submit, as it creates the required Kubernetes resources - (1) the driver pod that has the template applied to, and a (2) configmap storing the executor template for later use by the driver, - synchronously.

https://spark.apache.org/docs/latest/running-on-kubernetes.html#pod-template

I didn't include the regenerated CRDs in the PR. Further items to decide before moving forward:

• for the sake of keeping the diff small I modified the sparkoperator.k8s.io/v1beta2 version of the resource. I guess we want to create a new version for it.
• k8s.io is reserved for Kubernetes community maintained APIs. If I am not mistaken, this means we should move away from sparkoperator.k8s.io for our next version of the API.
• remove or deprecate all options that use the mutating web hooks for the next version?
• remove or deprecate options that doid not require mutating web hooks but can be set via pod templates now? e.g coreLimit, coreRequest
• make the main container name configurable with adding options controlling spark.kubernetes.driver.podTemplateContainerName and spark.kubernetes.executor.podTemplateContainerName confs

[dszakallas]

@liyinan926 could you take a look?

[elihschiff]

Do you have an example somewhere how to use podtemplate in sparkapplication. would be really cool. thanks

For anyone else who stumbles upon this issue, here is how I was able to do it:

1. Create a configmap for your pod template
2. Mount that configmap to the operator pod
3. Use the sparkConf setting on your SparkApplication to set the template file. Something like

sparkConf:
    spark.kubernetes.driver.podTemplateFile: "/etc/templates/pod_template.yaml"

[ahuret]

Hello 👋
We also experimented issues with webhook, it stops working sometimes.
What about this enhancement ? Any news ?
Thank you :-)

[gaurav-uptycs]

Hello
Facing this same issue when using webhook.
NodeAffinity is not being parsed in SparkApplication . Also webhook even though is deployed looks like the k8s cluster is not able to access it.
Please let me know if any of you know a way to bypass this.
Thanks .

[bscaleb]

@elihschiff does the spark-operator helm chart have any support for mounting a configmap to the operator pod? I don't see anything in the values or documentation. I definitely don't want to have to be manually editing the deployment in k8s.

[elihschiff]

Sorry this was 2 years ago, I don't remember exactly what I did. But I wouldn't be surprised if I had modified the helm chart to get it working