CreateContainerConfigError: the key that isn't there

The situation

A new status in your zoo:

NAME                       READY   STATUS                       RESTARTS   AGE
pricing-6b9d8c7f4d-tk3mx   0/1     CreateContainerConfigError   0          4m

Not CrashLoopBackOff (the app never ran — no logs). Not ImagePullBackOff (the image pulled fine). CreateContainerConfigError means the kubelet pulled the image, then tried to assemble the container's configuration — env vars, mounted keys — and couldn't. The pod is stuck before process start, and the answer lives in events:

kubectl -n kubelings describe pod -l app=pricing | tail -6

Error: couldn't find key taxRate in ConfigMap kubelings/pricing-config

The ConfigMap exists. It has tax_rate. The Deployment asks for taxRate. snake_case vs camelCase — a one-key typo, and the kubelet retries forever.

      ┌─────────────┐       
      │image pulled │       
      │             │       
      └─────────────┘       
             │              
         next step          
             │              
             ▼              
  ┌──────────────────────┐  
  │kubelet assembles env │  
  │                      │  
  └──────────────────────┘  
             │              
CreateContainerConfigError  
             │              
             ▼              
  ┌────────────────────────┐
  │missing key, no process │
  │                        │
  └────────────────────────┘

Your task

Get pricing Running with TAX_RATE=0.19 actually inside the container:

kubectl -n kubelings get configmap pricing-config -o yaml
kubectl -n kubelings get deploy pricing -o jsonpath='{.spec.template.spec.containers[0].env}'

Fix the mismatch from whichever side you think is right — but know that other services may read this ConfigMap too (changing the consumer is safer than changing the shared key).

Hint

kubectl -n kubelings patch deploy pricing --type=json -p '[
  {"op":"replace","path":"/spec/template/spec/containers/0/env/1/valueFrom/configMapKeyRef/key","value":"tax_rate"}
]'

Solution

Root cause

configMapKeyRef asked for key taxRate; the ConfigMap holds tax_rate. The kubelet cannot construct the env, so the container never starts. (Same failure shape for Secrets: couldn't find key … in Secret ….)

Fix

kubectl -n kubelings patch deploy pricing --type=json -p '[
  {"op":"replace","path":"/spec/template/spec/containers/0/env/1/valueFrom/configMapKeyRef/key","value":"tax_rate"}
]'
kubectl -n kubelings rollout status deploy/pricing

env vs mount — the difference that bites later

	`env` / `envFrom`	volume mount
read	copied at container start	file read at access time
ConfigMap edited	pod keeps old values until restarted	file updates in place (~1 min sync)
typo'd key	`CreateContainerConfigError`	mounts empty/missing file (silent!)

Both have failure modes: env fails loudly at start, mounts fail quietly at runtime. Pick env for boot-time constants, mounts for config you intend to reload — and remember editing a ConfigMap never restarts consumers; pair config changes with kubectl rollout restart or a checksum annotation.

Prevention

One naming convention per ConfigMap (snake_case or camelCase), enforced in review.
kubectl describe pod first for any Create…Error — the event names the exact missing key and object.

Course progress