Working with CR for version 6

[TheCodeAddiction]

Intro

I am trying to make an k8 operator that is going to watch and work with custom resources. I am finding a lot of documentation and guides on how to do this, before version 6. I am currently struggling to find up-to date documentation for version 6.

Prerequisite

1. I have applied my CRD to my k8 cluster.
2. I am running version 6.0.0 of fabric8 kubernetes-client, kubernetes-model and kubernetes-model-common

Question

I have created a KubernetesClient, using the KubernetesClientBuilder().build(); and I am able to watch changes to a specific pod, using the Watch class. Watch watch = client.pods().withName(podName).watch(new Watcher<Pod>(){...}

Now I want to watch a specific CR. As I understand I need to use Generic Resource API? The example code shows how to get a POD in a namespace Pod pod = client.resource(pod1).inNamespace("default").get();. However, I am having a couple of issues

1. It does not show what the argument pod1 is. Is it a string? an object? I can't find any documentation about the client, which I assume is a KubernetesClient, it should be located in the java doc, but it isn't.
2. Since I can't find any specific documentation, I am very unsure about how to, or if I can, use this on a CR.

I have been looking around on the docs here on github, but I am struggling to find any specific information on how to work with CR and I can't find any in-depth documentation about, for example, the KuberentesClient class and it's methods etc.
This might be a "me" problem, but I have googled in and out for a long time and read everywhere I can. Most online "tutorials" use an older version of fabric8. I have read the MIGRATION-v6.md document and tried to convert old fabric8 code to the newer version, but I am struggling to find in-depth documentation. It seems that if I had worked with fabric8, the migration guide would be amazing, but since I haven't I am a bit stuck.

TLDR:

1. How do I watch, GET and Create a CR with fabric8 version 6+
2. Is there any in-depth documentation like java doc that is up-to date? I can't find any information on, for example: KubernetesClient in the java doc

[rohanKanojia]

Have you checked these?

https://github.com/fabric8io/kubernetes-client/blob/master/doc/CHEATSHEET.md#resource-typed-api
https://github.com/fabric8io/kubernetes-client/blob/master/doc/CHEATSHEET.md#resource-typeless-api

[TheCodeAddiction]

I have no clue how I missed that, but this is great for creating CR!

Is there any in-depth documentation, like java doc, for the KuberentesClient class? I see the example code and can easily make it work, but I would love to read some specification without having to dive into the source code. Is that something that I have also missed?

[andreaTP]

@TheCodeAddiction as a reference exists a dedicated project to simplify writing operators in Java:
https://github.com/java-operator-sdk/java-operator-sdk

[TheCodeAddiction]

Yes, I know about Operator-SDK :) But we are testing out fabric8 at the place I work at currently, so Operator-SDK is no go for now.

[TheCodeAddiction]

@rohanKanojia I am trying to create a CR, however the documentation you linked above is:

1. Deprecated
2. A bit confusing

Detail

According to the documentation, to create a CR, you do: cronTabClient.inNamespace("default").create(cronTab1);

The issue is, the create() method is marked as deprecated. So is every other method in the ItemWritableOperation interface, what am I suppose to use instead?

Also, what is the cronTab1 argument? I assume it is an instance of the CronTab class? However, how do I create it correctly? Do I need to create a CronTabSpec and CronTabStatus object and do cronTab1.setSpec and cronTab1.setStatus? Do I need to create a metadata object and use cronTab1.setMetadata()? etc.

[rohanKanojia]

you're supposed to use resource()

cronTabClient.inNamespace("default").resource(cronTab1).create();

Yes, you'd need to create CronTab object manually. you can set metadata using ObjectMetaBuilder, however you'd need to populate spec manually. You can see my demo project for example https://github.com/rohanKanojia/kubernetes-client-demo/blob/master/src/main/java/io/fabric8/TypedCustomResourceDemoBlog.java

You're right about our documentation being outdated. Could you please create an issue about this 🙏 ?

[TheCodeAddiction]

Sure! I can create an issue :) if you need help I could also try to get find some time and help you guys update it :)

[rohanKanojia]

that would be great.