Kubernetes Sidecar Containers in v1.29

After years of workarounds, Kubernetes 1.29 introduces native sidecar container support via restartPolicy: Always in init containers.

The Old Way (Hack)

spec:
  containers:
    - name: app
      image: myapp:latest
    - name: istio-proxy
      image: istio/proxyv2

Problem: No startup/shutdown ordering guarantees.

The New Way (Native)

spec:
  initContainers:
    - name: istio-proxy
      image: istio/proxyv2
      restartPolicy: Always
  containers:
    - name: app
      image: myapp:latest

Why This Matters

1. Proper lifecycle - Sidecars start before and stop after main containers
2. Job support - Finally works correctly with batch workloads
3. Resource accounting - Cleaner resource limits

Migration Notes

Istio 1.20+ supports this natively. Enable with:

istioctl install --set values.pilot.env.ENABLE_NATIVE_SIDECARS=true