What is Kubernetes Service Link?

Question

Accepted Answer

**Service Links** — auto-inject environment variables for Services.

```yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  enableServiceLinks: false  # Disable service links
  containers:
  - name: app
    image: nginx:latest
---
# Default behavior (enableServiceLinks: true)
apiVersion: v1
kind: Pod
metadata:
  name: pod-with-links
spec:
  enableServiceLinks: true  # Default
  containers:
  - name: app
    image: nginx:latest
```

```bash
# Check service links
kubectl exec pod-with-links -- env | grep SERVICE

# Example environment variables injected:
# MY_SERVICE_SERVICE_HOST=10.96.0.10
# MY_SERVICE_SERVICE_PORT=80
# MY_SERVICE_PORT=tcp://10.96.0.10:80
# MY_SERVICE_PORT_80_TCP=tcp://10.96.0.10:80
# MY_SERVICE_PORT_80_TCP_PROTO=tcp
# MY_SERVICE_PORT_80_TCP_PORT=80
# MY_SERVICE_PORT_80_TCP_ADDR=10.96.0.10

# Check if service links are enabled
kubectl get pod my-pod -o jsonpath='{.spec.enableServiceLinks}'

# Count injected variables
kubectl exec pod-with-links -- env | grep SERVICE | wc -l
```

**Behavior:**
- Injected as environment variables.
- Names: SERVICE_NAME_SERVICE_HOST, SERVICE_NAME_SERVICE_PORT.
- Can cause environment explosion with many Services.

**Best Practices:**
- Disable (enableServiceLinks: false) for most Pods.
- Use DNS instead of environment variables.
- Only enable if needed for legacy applications.

DevOps: What is Kubernetes Service Link?