Sidecar Reference

The Vexil sidecar is an optional component that runs alongside your application pod, exposing feature flags via a local HTTP API with real-time SSE streaming.

Endpoints

Method	Path	Description
GET	/flags	All flags as JSON array
GET	/flags/{name}	Single flag as JSON
GET	/flags/{name}/value	Raw flag value as plain text
GET	/flags/stream	SSE stream of flag changes
GET	/healthz	Health check

Flag Response Format

{
  "name": "dark-mode",
  "type": "boolean",
  "value": "true",
  "disabled": false,
  "description": "Enable dark mode"
}

SSE Streaming

Connect to /flags/stream to receive real-time updates:

curl localhost:8514/flags/stream

Events are sent as:

event: update
data: {"name":"dark-mode","type":"boolean","value":"true","disabled":false}

A new event is sent whenever any flag in the namespace changes.

Configuration

Environment Variable	Default	Description
VEXIL_NAMESPACE	from serviceaccount or default	Namespace to watch for FeatureFlags
VEXIL_SIDECAR_PORT	8514	HTTP listen port

The sidecar binds to 127.0.0.1 only (not externally accessible).

Deployment

The sidecar is typically added as a container in your pod spec:

spec:
  containers:
    - name: app
      image: my-app:latest
      env:
        - name: VEXIL_SIDECAR_ADDR
          value: "http://localhost:8514"
    - name: vexil-sidecar
      image: ghcr.io/vexil-platform/sidecar:latest
      env:
        - name: VEXIL_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
      ports:
        - containerPort: 8514
          name: sidecar
      livenessProbe:
        httpGet:
          path: /healthz
          port: sidecar
        initialDelaySeconds: 5
      resources:
        requests:
          cpu: 10m
          memory: 32Mi
        limits:
          cpu: 50m
          memory: 64Mi