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simple-rl-for-app-developers.md

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Simple Rate Limiting for Application Developers

This user guide walks you through an example of how to configure rate limiting for an endpoint of an application using Kuadrant.


In this guide, we will rate limit a sample REST API called Toy Store. In reality, this API is just an echo service that echoes back to the user whatever attributes it gets in the request. The API listens to requests at the hostname api.toystore.com, where it exposes the endpoints GET /toys* and POST /toys, respectively, to mimic operations of reading and writing toy records.

We will rate limit the POST /toys endpoint to a maximum of 5rp10s ("5 requests every 10 seconds").


Run the steps ① → ③

① Setup

This step uses tooling from the Kuadrant Operator component to create a containerized Kubernetes server locally using Kind, where it installs Istio, Kubernetes Gateway API and Kuadrant itself.

Note: In production environment, these steps are usually performed by a cluster operator with administrator privileges over the Kubernetes cluster.

Clone the project:

git clone https://github.com/Kuadrant/kuadrant-operator && cd kuadrant-operator

Setup the environment:

make local-setup

Request an instance of Kuadrant:

kubectl -n kuadrant-system apply -f - <<EOF
apiVersion: kuadrant.io/v1beta1
kind: Kuadrant
metadata:
  name: kuadrant
spec: {}
EOF

② Deploy the Toy Store API

Create the deployment:

kubectl apply -f examples/toystore/toystore.yaml

Create a HTTPRoute to route traffic to the service via Istio Ingress Gateway:

kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: toystore
spec:
  parentRefs:
  - name: kuadrant-ingressgateway
    namespace: gateway-system
  hostnames:
  - api.toystore.com
  rules:
  - matches:
    - method: GET
      path:
        type: PathPrefix
        value: "/toys"
    backendRefs:
    - name: toystore
      port: 80
  - matches: # it has to be a separate HTTPRouteRule so we do not rate limit other endpoints
    - method: POST
      path:
        type: Exact
        value: "/toys"
    backendRefs:
    - name: toystore
      port: 80
EOF

Export the gateway hostname and port:

export INGRESS_HOST=$(kubectl get gtw kuadrant-ingressgateway -n gateway-system -o jsonpath='{.status.addresses[0].value}')
export INGRESS_PORT=$(kubectl get gtw kuadrant-ingressgateway -n gateway-system -o jsonpath='{.spec.listeners[?(@.name=="http")].port}')
export GATEWAY_URL=$INGRESS_HOST:$INGRESS_PORT

Verify the route works:

curl -H 'Host: api.toystore.com' http://$GATEWAY_URL/toys -i
# HTTP/1.1 200 OK

Note: If the command above fails to hit the Toy Store API on your environment, try forwarding requests to the service and accessing over localhost:

kubectl port-forward -n gateway-system service/kuadrant-ingressgateway-istio 9080:80 >/dev/null 2>&1 &
export GATEWAY_URL=localhost:9080
curl -H 'Host: api.toystore.com' http://$GATEWAY_URL/toys -i
# HTTP/1.1 200 OK

③ Enforce rate limiting on requests to the Toy Store API

Create a Kuadrant RateLimitPolicy to configure rate limiting:

kubectl apply -f - <<EOF
apiVersion: kuadrant.io/v1
kind: RateLimitPolicy
metadata:
  name: toystore
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: toystore
  limits:
    "create-toy":
      rates:
      - limit: 5
        window: 10s
      when:
      - predicate: "request.method == 'POST'"
EOF

Note: It may take a couple of minutes for the RateLimitPolicy to be applied depending on your cluster.


Verify the rate limiting works by sending requests in a loop.

Up to 5 successful (200 OK) requests every 10 seconds to POST /toys, then 429 Too Many Requests:

while :; do curl --write-out '%{http_code}\n' --silent --output /dev/null -H 'Host: api.toystore.com' http://$GATEWAY_URL/toys -X POST | grep -E --color "\b(429)\b|$"; sleep 1; done

Unlimited successful (200 OK) to GET /toys:

while :; do curl --write-out '%{http_code}\n' --silent --output /dev/null -H 'Host: api.toystore.com' http://$GATEWAY_URL/toys | grep -E --color "\b(429)\b|$"; sleep 1; done

Cleanup

make local-cleanup