[workloadmeta] Add support for "labels as tags"

[davidor]

What does this PR do?

Introduces a new option "container_labels_as_tags" that allows the agent to extract container label values and set them as metric tags values. It's equivalent to the existing "docker_labels_as_tags", but it also works with containerd.

This PR also adds support for that new option in the tagger workloadmeta collector.

This PR also fixes a regression. The new containerd collector didn't support advanced options in env as tags like: '{"*":"_%%env%%"}'. That has been fixed.

Describe how to test your changes

This needs to be tested on Kubernetes. Also, this only works in containerd >= 1.5.6 because previous versions didn't propagate labels correctly. At the moment of writing this, kind does not come with that containerd version by default, but you can install it in a custom image like explained here: kubernetes-sigs/kind#1637 (comment)

• Set DD_CONTAINER_LABELS_AS_TAGS to: "{"test_label": "test_label_as_tag"}", for example.
• Deploy the agent on Kubernetes.
• Build a Docker image with labels and deploy it to your Kubernetes cluster. For example:

FROM redis
LABEL test_label=test_val

• Check agent tagger-list and verify that the tag "test_label_as_tag" has the value "test_val" in the workloadmeta-container section of the container that you deployed.
• Check that advanced "as tags" configs (documented here) work. Both with envs and tags. You can try something like: set DD_CONTAINER_ENV_AS_TAGS to {"*":"ENVPREFIX_%%env%%"} and set DD_CONTAINER_LABELS_AS_TAGS to {"*":"LABELPREFIX_%%label%%"}. You should see those prefixes in agent tagger-list.

Checklist

• A release note has been added or the changelog/no-changelog label has been applied.
• The need-change/operator and need-change/helm labels has been applied if applicable.
• The appropriate team/.. label has been applied, if known.
• If known, an appropriate milestone has been selected; otherwise the Triage milestone is set.
• The config template has been updated if applicable.

Note: Adding GitHub labels is only possible for contributors with write access.

[davidor]

Rebased on top of master to get the latest changes in the workloadmeta code.

[ahmed-mez]

Thanks! ✅

Could you just update the PR description / testing section to mention that container_env_as_tags and container_labels_as_tags should support and be tested with advanced configs like '{"*":"<PREFIX>_%%label%%"}' as documented here ? thanks!

[davidor]

@ahmed-mez I updated the PR description and testing instructions.