[CONTINT-1132] Send in-<inode> using the cgroup controller when container-id cannot be retrieved

[AliDatadog]

Implementation of https://github.com/DataDog/datadog-go/pull/291 but in Java

This Pull Request implements the support of Origin Detection when the container-id is unavailable from inside the application container only with cgroupv2.

It first retrieves the cgroup node path by parsing proc/self/cgroup which is formatted differently depending on the cgroup version. See https://man7.org/linux/man-pages/man7/cgroups.7.html.

The format is a list of hierarchy-ID:controller-list:cgroup-path similar to:

0:: 1:name=systemd:... // only in cgroupv1 Once the path is retrieved, we retrieve the inode of /sys/fs/cgroup + + where is the path retrieved previously.

I am not sure how to create a dummy app that uses this library.

Test

• Set up a cgroupv2 environment. A kind cluster should be enough.
• Deploy the agent 7.51.0+ with origin detection and dogstatsd enabled. Using helm:

  dogstatsd:
  port: 8125
  originDetection: true
  useHostPort: true
  useHostPID: true
  tagCardinality: high

• Note that you will also need the env var:

  - name: "DD_DOGSTATSD_ORIGIN_DETECTION_CLIENT"
    value: "true"

• Deploy a dummy app. I already made one with and without this change:

  apiVersion: apps/v1
  kind: Deployment
  metadata:
  name: my-java-dsd-app
  spec:
  replicas: 1
  selector:
  matchLabels:
    app: my-java-dsd-app
  template:
  metadata:
    labels:
      app: my-java-dsd-app
      admission.datadoghq.com/enabled: "false"
  spec:
    containers:
    - name: my-java-dsd-app
      image: docker.io/alidatadog/dummy-java-dsd-app:with-inode@sha256:a62e653e3c8e493611ba5841d3af94921edef0670776d0555fed9eecc2b50341 # use the tag without-inode for comparison
      imagePullPolicy: Always
      env:
      - name: DD_AGENT_HOST
        valueFrom:
          fieldRef:
            fieldPath: status.hostIP

• Verify that dummy.metric is correctly tagged with container-id when it wasn't before. If you are curious about the dummy app, I pushed it here https://github.com/AliDatadog/dummy-dsd-java-app.