init-containers.md

Instrumenting Init Containers

Init containers can be instrumented by including their names in the container-names annotation. When an init container is targeted for instrumentation, the operator automatically inserts the instrumentation init container before the target init container in the pod's init container sequence. This ensures the instrumentation agent files are available when the target init container runs.

Supported instrumentations for init containers:

• Java
• Python
• Node.js
• .NET
• SDK-only injection

Not supported for init containers:

• Go (does not support multicontainer pods)
• Apache HTTPD
• Nginx

Note: Kubernetes guarantees that container names are unique across both the initContainers and containers lists within a pod spec. This allows the operator to unambiguously identify whether a container name refers to an init container or a regular container.

Example with both init container and regular container instrumentation:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment-with-init-container
spec:
  selector:
    matchLabels:
      app: my-app
  replicas: 1
  template:
    metadata:
      labels:
        app: my-app
      annotations:
        instrumentation.opentelemetry.io/inject-python: "true"
        instrumentation.opentelemetry.io/container-names: "my-init-job,myapp"
    spec:
      initContainers:
        - name: my-init-job
          image: my-python-init-image
      containers:
        - name: myapp
          image: my-python-app-image

In this example, both my-init-job (an init container) and myapp (a regular container) will be instrumented with Python auto-instrumentation.