Kubernetes Sidecar Injector

This repo contains the complete code for my Kubernetes Sidecar Container Injection Medium article to create a Kubernetes mutating admission controller that injects a busybox-curl sidecar container into pods.

Requirments

• Docker
• kubectl
• Helm
• Access to a Kubernetes v1.19+ cluster

Deploying

1. Install the kubernetes-sidecar-injector chart

helm install kubernetes-sidecar-injector charts/kubernetes-sidecar-injector/ \
--values charts/kubernetes-sidecar-injector/values.yaml \
--namespace default

2. Install the httpbin chart

helm install httpbin charts/httpbin/ \
--values charts/httpbin/values.yaml \
--namespace default

3. Listing all containers in the httpbin Deployment's Pod, you can notice that a new container is running in it named curl.

export POD_NAME=$(kubectl get pods \
--namespace default \
-l "app.kubernetes.io/name=httpbin,app.kubernetes.io/instance=httpbin" \
-o jsonpath="{.items[0].metadata.name}")

kubectl get pods $POD_NAME \
--namespace default \
-o jsonpath='{.spec.containers[*].name}'

4. Accessing the httpbin HTTP server from inside the curl container.

export POD_NAME=$(kubectl get pods \
--namespace default \
-l "app.kubernetes.io/name=httpbin,app.kubernetes.io/instance=httpbin" \
-o jsonpath="{.items[0].metadata.name}")

kubectl exec $POD_NAME \
--namespace default \
-c curl \
-- curl http://localhost/anything