feat(discovery): port kubeApi discovery to v3

[tthvo]

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---

Fixes: #238

Description of the change:

Port KubeDiscoveryAPI from v2 to v3.

Motivation for the change:

See #238

How to manually test:

Build the application and push to quay.io:

IMAGE_NAMESPACE=quay.io/thvo
./mvnw clean package -DskipTests=true && \
podman tag quay.io/cryostat/cryostat:3.0.0-snapshot ${IMAGE_NAMESPACE}/cryostat:3.0.0-snapshot && \
podman push ${IMAGE_NAMESPACE}/cryostat:3.0.0-snapshot

Install the application with Helm Chart (cryostatio/cryostat-helm#128):

helm install cryostat3 ./charts/cryostat/ \
  --set core.discovery.kubernetes.enabled=true \
  --set core.discovery.kubernetes.namespaces="{default,myns,.}" \
  --set core.discovery.kubernetes.portNames="{jmx-jfr,my-port}" \
  --set core.discovery.kubernetes.portNumbers="{9091,9097}" \
  --set core.image.repository=${IMAGE_NAMESPACE}/cryostat

Deploy/Scale/Teardown sample applications:

cd cryostat-operator && make sample_app # or make undeploy_sample_app

[andrewazores]

In 2.4, the NAMESPACES env var was expected to be simply a comma-separated list of namespaces that Cryostat should try to set up an informer for. If the env var was not set then it would default to an empty list - no discovery.

I think in 3.0 we want to preserve that same behaviour, however with one addition: a special character that signifies "your own namespace", as in the namespace that the Cryostat Pod is running within. I suggest . for this special character. This can be included in the namespace list, so it would be possible for the user to set the variable to a,b,.. Cryostat should try to look up what its own namespace is, map . to that value, then deduplicate the namespace list (in case . is equal to a or b). This way configuration is a little bit simpler. I think we can also default the namespace list to the . singleton rather than defaulting to empty.

[tthvo]

In 2.4, the NAMESPACES env var was expected to be simply a comma-separated list of namespaces that Cryostat should try to set up an informer for. If the env var was not set then it would default to an empty list - no discovery.

I think in 3.0 we want to preserve that same behaviour, however with one addition: a special character that signifies "your own namespace", as in the namespace that the Cryostat Pod is running within. I suggest . for this special character. This can be included in the namespace list, so it would be possible for the user to set the variable to a,b,.. Cryostat should try to look up what its own namespace is, map . to that value, then deduplicate the namespace list (in case . is equal to a or b). This way configuration is a little bit simpler. I think we can also default the namespace list to the . singleton rather than defaulting to empty.

Oh thank you! This behaviour with . makes sense to me. I suppose we would want the default namespace list to empty and require it to be explicitly set in a similar way to other configurations (e.g. cryostat.discovery.k8s.port-names)?

[andrewazores]

Sure, I think for the individual Cryostat container level it makes sense to default to empty lists there. We can apply default values in the Helm chart, in Operator CRs, and maybe also in Operator default webhooks.

[tthvo]

/build_test

[github-actions]

Workflow started at 4/24/2024, 2:05:13 PM. View Actions Run.

[github-actions]

No OpenAPI schema changes detected.

[github-actions]

No GraphQL schema changes detected.

[github-actions]

CI build and push: At least one test failed ❌ (JDK17)
https://github.com/cryostatio/cryostat3/actions/runs/8821181398

[tthvo]

/build_test

[github-actions]

Workflow started at 4/24/2024, 2:25:51 PM. View Actions Run.

[github-actions]

No GraphQL schema changes detected.

[github-actions]

No OpenAPI schema changes detected.

[github-actions]

CI build and push: All tests pass ✅ (JDK17)
https://github.com/cryostatio/cryostat3/actions/runs/8821461039

[tthvo]

Phew tests failure and spotbugs errors are fixed now^^ I did manual tests with container, jdp and custom discovery as this PR also affects them. They are all fine.