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WebMethods Gateway + STOA Sidecar Integration

This guide explains how to deploy Software AG webMethods API Gateway with STOA sidecar for policy enforcement, rate limiting, and usage metering.

ADR Reference

This integration uses ADR-036: Gateway Auto-Registration and ADR-035: Gateway Adapter Pattern.

Architecture Overview​

┌─────────────────────────────────────────────────────────────────┐
│                        Kubernetes Pod                           │
│  ┌──────────────────────┐    ┌───────────────────────────────┐  │
│  │   webMethods API     │    │      STOA Sidecar             │  │
│  │      Gateway         │    │    (sidecar mode)             │  │
│  │                      │    │                               │  │
│  │  ┌────────────────┐  │    │  ┌─────────────────────────┐  │  │
│  │  │   ext_authz    │──┼────┼──│  /authz endpoint       │  │  │
│  │  │   filter       │  │    │  │  - OPA policies        │  │  │
│  │  └────────────────┘  │    │  │  - Rate limiting       │  │  │
│  │                      │    │  │  - Token validation    │  │  │
│  │  Port: 9072          │    │  └─────────────────────────┘  │  │
│  │  (API traffic)       │    │                               │  │
│  └──────────────────────┘    │  Port: 8081                   │  │
│                              │  (internal only)              │  │
│                              │                               │  │
│                              │  ┌─────────────────────────┐  │  │
│                              │  │  Auto-registration      │  │  │
│                              │  │  → Control Plane        │  │  │
│                              │  └─────────────────────────┘  │  │
│                              └───────────────────────────────┘  │
└─────────────────────────────────────────────────────────────────┘

Prerequisites​

  1. STOA Control Plane deployed and accessible
  2. Keycloak realm stoa configured
  3. Gateway API keys configured in Control Plane (see Gateway Auto-Registration Guide)

Deployment​

1. Create Secrets​

kubectl create secret generic stoa-sidecar-secrets \
  --namespace stoa-system \
  --from-literal=control-plane-api-key="gw_your_api_key_here" \
  --from-literal=keycloak-client-secret="your_keycloak_secret"

2. Configure Helm Values​

Create a values-webmethods.yaml file:

stoaSidecar:
  enabled: true
  targetGateway: webmethods

  # STOA Sidecar configuration
  image:
    repository: 848853684735.dkr.ecr.eu-west-1.amazonaws.com/apim/stoa-gateway
    tag: latest

  environment: prod
  controlPlaneUrl: "https://api.<YOUR_DOMAIN>"
  keycloakUrl: "https://auth.<YOUR_DOMAIN>"
  keycloakRealm: stoa
  keycloakClientId: stoa-sidecar
  secretName: stoa-sidecar-secrets

  # webMethods Gateway configuration
  mainGateway:
    enabled: true
    image:
      repository: softwareag/webmethods-api-gateway
      tag: "10.15"
    port: 9072
    env:
      - name: JAVA_OPTS
        value: "-Xms1g -Xmx2g"
      - name: SAG_IS_LICENSE_KEY
        valueFrom:
          secretKeyRef:
            name: webmethods-license
            key: license-key
      # Enable ext_authz to point to STOA sidecar
      - name: apigw_ext_authz_enabled
        value: "true"
      - name: apigw_ext_authz_url
        value: "http://127.0.0.1:8081/authz"
    resources:
      requests:
        cpu: 1000m
        memory: 2Gi
      limits:
        cpu: 4000m
        memory: 8Gi

3. Deploy​

helm upgrade --install stoa-webmethods ./charts/stoa-platform \
  --namespace stoa-system \
  --values values-webmethods.yaml

How It Works​

1. Auto-Registration​

When the pod starts, the STOA sidecar automatically registers with the Control Plane:

POST /v1/internal/gateways/register
{
  "hostname": "webmethods-with-stoa-sidecar-xyz",
  "mode": "sidecar",
  "version": "0.1.0",
  "environment": "prod",
  "capabilities": ["ext_authz", "rate_limiting", "metering", "oidc"],
  "admin_url": "http://10.0.1.50:8081"
}

2. Request Flow​

  1. Client → webMethods Gateway (port 9072)
  2. webMethods → ext_authz → STOA sidecar (port 8081)
  3. STOA sidecar evaluates:
    • OPA policies (loaded from Control Plane)
    • Rate limits (per tenant/API/user)
    • JWT token validation (via Keycloak)
  4. Decision returned to webMethods (allow/deny)
  5. If allowed, webMethods → Backend API
  6. STOA sidecar → Kafka (usage metrics)

3. Heartbeat​

The sidecar sends heartbeats every 30 seconds:

POST /v1/internal/gateways/{gateway_id}/heartbeat
{
  "uptime_seconds": 3600,
  "routes_count": 0,
  "policies_count": 5,
  "requests_total": 10000,
  "error_rate": 0.01
}

Monitoring​

Console View​

The webMethods + STOA sidecar appears in the STOA Console at /gateways:

NameTypeStatusEnvironment
webmethods-prod-abc123stoa_sidecarONLINEprod

Prometheus Metrics​

The sidecar exposes Prometheus metrics at http://localhost:8081/metrics:

stoa_sidecar_requests_total{tenant="acme",api="billing",status="allowed"} 9500
stoa_sidecar_requests_total{tenant="acme",api="billing",status="denied"} 500
stoa_sidecar_policy_evaluation_duration_seconds_bucket{le="0.01"} 9800
stoa_sidecar_rate_limit_hits_total{tenant="acme"} 150

Policies​

Creating a Rate Limit Policy​

curl -X POST ${STOA_API_URL}/v1/admin/policies \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "rate-limit-100rpm",
    "policy_type": "rate_limit",
    "scope": "api",
    "config": {
      "requests_per_minute": 100,
      "burst_size": 10
    },
    "priority": 100
  }'

Binding Policy to Gateway​

curl -X POST ${STOA_API_URL}/v1/admin/policies/bindings \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "policy_id": "UUID_FROM_ABOVE",
    "gateway_instance_id": "UUID_OF_WEBMETHODS_SIDECAR"
  }'

Troubleshooting​

Sidecar Not Registering​

Check logs:

kubectl logs -n stoa-system deployment/webmethods-with-stoa-sidecar -c stoa-sidecar

Verify Control Plane URL is reachable:

kubectl exec -n stoa-system deployment/webmethods-with-stoa-sidecar -c stoa-sidecar -- \
  curl -s http://control-plane-api.stoa-system.svc.cluster.local:8000/health

ext_authz Errors​

Check webMethods logs for ext_authz connection issues:

kubectl logs -n stoa-system deployment/webmethods-with-stoa-sidecar -c webmethods

Test ext_authz endpoint directly:

kubectl exec -n stoa-system deployment/webmethods-with-stoa-sidecar -c webmethods -- \
  curl -s http://127.0.0.1:8081/authz -X POST -H "Content-Type: application/json" -d '{}'

Gateway Shows OFFLINE​

If the gateway shows OFFLINE in Console but is running:

  1. Check heartbeat is being sent:

    kubectl logs -n stoa-system deployment/webmethods-with-stoa-sidecar -c stoa-sidecar | grep heartbeat

  2. Verify Control Plane API key:

    kubectl get secret stoa-sidecar-secrets -n stoa-system -o jsonpath='{.data.control-plane-api-key}' | base64 -d

  3. Ensure the API key is in the GATEWAY_API_KEYS list in Control Plane config.