Skills
skills/pjt222/development-guides/configure-api-gateway

configure-api-gateway

SKILL.md

Configure API Gateway

Deploy and configure an API gateway for centralized API traffic management and policy enforcement.

When to Use

  • Multiple backend services need unified API endpoint with consistent policies
  • Require centralized authentication/authorization for API access
  • Need rate limiting and quota management across APIs
  • Want to transform requests/responses without modifying backend services
  • Implementing API versioning and deprecation strategies
  • Need detailed API analytics and monitoring
  • Require service discovery and load balancing for microservices

Inputs

  • Required: Kubernetes cluster or Docker environment
  • Required: Choice of API gateway (Kong or Traefik)
  • Required: Backend service endpoints to proxy
  • Optional: Authentication provider (OAuth2, OIDC, API keys)
  • Optional: Rate limiting requirements (requests per minute/hour)
  • Optional: Custom middleware or plugin configurations
  • Optional: TLS certificates for HTTPS endpoints

Procedure

See Extended Examples for complete configuration files and templates.

Step 1: Install API Gateway

Deploy the API gateway with database (Kong) or file-based config (Traefik).

For Kong with PostgreSQL:

# kong-deployment.yaml (excerpt - see EXAMPLES.md for complete file)
apiVersion: v1
kind: Namespace
metadata:
  name: kong
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: kong
  namespace: kong
spec:
  replicas: 2
  # ... (PostgreSQL, migrations, services - see EXAMPLES.md)

For Traefik:

# traefik-deployment.yaml (excerpt - see EXAMPLES.md for complete file)
apiVersion: v1
kind: Namespace
metadata:
  name: traefik
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: traefik
  namespace: traefik
spec:
  replicas: 2
  # ... (RBAC, ConfigMap, services - see EXAMPLES.md)

See EXAMPLES.md for the complete deployment manifests

Deploy:

kubectl apply -f kong-deployment.yaml  # OR traefik-deployment.yaml
kubectl wait --for=condition=ready pod -l app=kong -n kong --timeout=300s
kubectl get svc -n kong kong-proxy  # Get load balancer IP

Expected: Gateway pods running with 2 replicas. Load balancer service has external IP assigned. Admin API accessible (Kong: port 8001, Traefik: dashboard port 8080). Health checks passing.

On failure:

  • Check pod logs: kubectl logs -n kong -l app=kong
  • Verify database connection (Kong): kubectl logs -n kong kong-migrations-<hash>
  • Check service account permissions (Traefik): kubectl get clusterrolebinding traefik -o yaml
  • Ensure ports not already bound: kubectl get svc --all-namespaces | grep 8000

Step 2: Configure Backend Services and Routes

Define upstream services and create routes to expose APIs.

For Kong (using decK for declarative config):

# Install decK CLI
curl -sL https://github.com/Kong/deck/releases/download/v1.28.0/deck_1.28.0_linux_amd64.tar.gz | tar -xz
sudo mv deck /usr/local/bin/

# Create kong.yaml with services, routes, upstreams
# (see EXAMPLES.md for complete configuration)
deck sync --kong-addr http://localhost:8001 -s kong.yaml
curl -i http://localhost:8001/routes  # Verify routes

For Traefik (using IngressRoute CRD):

# traefik-routes.yaml (excerpt)
apiVersion: traefik.io/v1alpha1
kind: IngressRoute
metadata:
  name: user-api-route
spec:
  entryPoints: [websecure]
  routes:
  - match: Host(`api.example.com`) && PathPrefix(`/api/users`)
    # ... (see EXAMPLES.md for full configuration)

Apply routes:

kubectl apply -f traefik-routes.yaml
curl -H "Host: api.example.com" https://GATEWAY_IP/api/users

See EXAMPLES.md for complete routing configurations

Expected: Routes correctly proxy traffic to backend services. Weighted routing distributes traffic according to configuration. Health checks monitor backend service health.

On failure:

  • Verify backend services running: kubectl get svc -n default
  • Check DNS resolution: kubectl run test --rm -it --image=busybox -- nslookup user-service.default.svc.cluster.local
  • Review gateway logs: kubectl logs -n kong -l app=kong --tail=50
  • Validate configuration: deck validate -s kong.yaml

Step 3: Implement Authentication and Authorization

Configure authentication plugins/middleware for API security.

For Kong (API Key and JWT authentication):

# kong-auth-config.yaml (excerpt)
consumers:
- username: mobile-app
  custom_id: app-001

keyauth_credentials:
- consumer: mobile-app
  key: mobile-secret-key-123

plugins:
- name: key-auth
  service: user-api
  # ... (see EXAMPLES.md for full configuration)

deck sync --kong-addr http://localhost:8001 -s kong-auth-config.yaml
curl -i -H "apikey: mobile-secret-key-123" http://GATEWAY_IP/api/users

For Traefik (BasicAuth and ForwardAuth middleware):

# traefik-auth-middleware.yaml (excerpt)
apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: basic-auth-middleware
spec:
  basicAuth:
    secret: basic-auth
    removeHeader: true
# ... (see EXAMPLES.md for OAuth2, rate limiting)

kubectl apply -f traefik-auth-middleware.yaml
curl -u user1:password https://GATEWAY_IP/api/protected

See EXAMPLES.md for complete authentication configurations

Expected: Unauthenticated requests return 401. Valid credentials allow access. Rate limiting returns 429 after threshold. JWT tokens validate correctly. ACL enforces group permissions.

On failure:

  • Verify consumer creation: curl http://localhost:8001/consumers
  • Check plugin enabled: curl http://localhost:8001/plugins | jq .
  • Test with verbose: curl -v to see response headers
  • Validate JWT: use jwt.io to decode token

Step 4: Configure Request/Response Transformation

Add middleware to transform requests and responses.

For Kong:

# kong-transformations.yaml (excerpt)
plugins:
- name: request-transformer
  service: user-api
  config:
    add:
      headers: [X-Gateway-Version:1.0, X-Request-ID:$(uuid)]
    remove:
      headers: [X-Internal-Token]
- name: correlation-id
  # ... (see EXAMPLES.md for full configuration)

deck sync --kong-addr http://localhost:8001 -s kong-transformations.yaml

For Traefik:

# traefik-transformations.yaml (excerpt)
apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: add-headers
spec:
  headers:
    customRequestHeaders:
      X-Gateway-Version: "1.0"
    # ... (see EXAMPLES.md for circuit breaker, retry, chain)

kubectl apply -f traefik-transformations.yaml
curl -v https://GATEWAY_IP/api/users | grep X-Gateway

See EXAMPLES.md for complete transformation configurations

Expected: Request headers added/removed as configured. Response headers include gateway metadata. Large requests rejected with 413. Circuit breaker trips on repeated failures. Retries occur for transient errors.

On failure:

  • Verify middleware order in chain
  • Check for header conflicts with backend services
  • Test transformations individually before chaining
  • Review logs for transformation errors

Step 5: Enable Monitoring and Analytics

Configure metrics, logging, and dashboards for API visibility.

Kong monitoring setup:

# kong-monitoring.yaml (excerpt)
plugins:
- name: prometheus
  config:
    per_consumer: true
- name: http-log
  service: user-api
  # ... (see EXAMPLES.md for Datadog, file-log configuration)

deck sync --kong-addr http://localhost:8001 -s kong-monitoring.yaml

# Deploy ServiceMonitor (see EXAMPLES.md)
kubectl apply -f kong-servicemonitor.yaml
curl http://localhost:8100/metrics

Traefik monitoring (built-in):

# ServiceMonitor (excerpt - see EXAMPLES.md for Grafana dashboard)
apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: traefik-metrics
spec:
  endpoints:
  - port: metrics
    path: /metrics
    interval: 30s

kubectl port-forward -n traefik svc/traefik-dashboard 8080:8080
# Open http://localhost:8080/dashboard/

See EXAMPLES.md for complete monitoring configurations

Expected: Prometheus scraping gateway metrics successfully. Dashboards show request rates, latency percentiles, error rates. Logs forwarding to aggregation system. Metrics segmented by service, route, and consumer.

On failure:

  • Verify ServiceMonitor: kubectl get servicemonitor -A
  • Check Prometheus targets in UI
  • Ensure metrics port accessible: kubectl port-forward -n kong svc/kong-metrics 8100:8100
  • Validate log endpoint reachability

Step 6: Implement API Versioning and Deprecation

Configure version management and graceful API deprecation.

Kong versioning strategy:

# kong-versioning.yaml (excerpt)
services:
- name: user-api-v1
  url: http://user-service-v1.default.svc.cluster.local:8080
  routes:
  - name: user-v1-route
    paths: [/api/v1/users]
  plugins:
  - name: response-transformer
    config:
      add:
        headers:
        - X-Deprecation-Notice:"API v1 deprecated on 2024-12-31"
        - Sunset:"Wed, 31 Dec 2024 23:59:59 GMT"
# ... (see EXAMPLES.md for v2, default routing, rate limits)

Traefik versioning:

# traefik-versioning.yaml (excerpt)
apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: v1-deprecation-headers
spec:
  headers:
    customResponseHeaders:
      X-Deprecation-Notice: "API v1 deprecated on 2024-12-31"
# ... (see EXAMPLES.md for complete IngressRoutes)

Test versioning:

curl -i https://api.example.com/api/v1/users  # Deprecated
curl -i https://api.example.com/api/v2/users  # Current
curl -i https://api.example.com/api/users     # Routes to v2

See EXAMPLES.md for complete versioning configurations

Expected: Different versions route to appropriate backend services. Deprecation headers present on v1 responses. Rate limits stricter for deprecated versions. Default path routes to latest version. Metrics segmented by API version.

On failure:

  • Verify path precedence/priority configuration (higher priority = evaluated first)
  • Check for overlapping path patterns
  • Test each version route independently
  • Review routing logs for path matching
  • Ensure backend services for each version are running

Validation

  • API gateway pods running with multiple replicas for HA
  • Load balancer service has external IP assigned
  • Routes correctly proxy traffic to backend services
  • Authentication/authorization enforcing access control (401/403 responses)
  • Rate limiting returns 429 after exceeding quotas
  • Request/response transformation adding/removing headers correctly
  • Circuit breaker trips on repeated backend failures
  • Metrics exposed and scraped by Prometheus
  • Dashboards showing request rates, latency, errors
  • API versioning routing requests to correct backend versions
  • Deprecation headers present on older API versions
  • Health checks monitoring backend service availability

Common Pitfalls

  • Database Dependency (Kong): Kong with database requires PostgreSQL/Cassandra. DB-less mode available but limits some features (runtime config changes). Use DB mode for production with multiple gateway instances.

  • Path Matching Order: Routes/IngressRoutes evaluated in specific order. More specific paths should have higher priority. Overlapping paths cause unpredictable routing. Test with curl -v to verify actual route hit.

  • Authentication Bypass: Ensure authentication plugins applied to all routes. Easy to add route without auth. Use default plugins at service level, then override per-route as needed.

  • Rate Limit Scope: Rate limiting policy: local counts per gateway pod. For consistent limits across replicas, use centralized policy (Redis) or sticky sessions.

  • CORS Configuration: API gateway should handle CORS, not individual services. Add CORS plugin/middleware early to avoid browser preflight failures.

  • SSL/TLS Termination: Gateway typically terminates SSL. Ensure certificates valid and auto-renewal configured. Use cert-manager for Kubernetes certificate management.

  • Upstream Health Checks: Configure active health checks to detect backend failures quickly. Passive checks rely on real traffic and may be slower to detect issues.

  • Plugin/Middleware Execution Order: Order matters. Authentication before rate limiting (avoid wasted rate limit slots for invalid requests). Transformation before logging (log transformed values).

  • Resource Limits: Gateway pods can consume significant CPU under load. Set appropriate resource requests/limits. Monitor CPU throttling in production.

  • Migration Strategy: Don't enable all plugins at once. Roll out incrementally: routing → authentication → rate limiting → transformations → advanced features.

Related Skills

  • configure-ingress-networking - Ingress controller setup complements API gateway
  • setup-service-mesh - Service mesh provides complementary east-west traffic management
  • manage-kubernetes-secrets - Certificate and credential management for gateway
  • setup-prometheus-monitoring - Monitoring integration for gateway metrics
  • enforce-policy-as-code - Policy enforcement that complements gateway authorization
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