Local Rate Limit

5 minute read

Rate limit is a feature that allows the user to limit the number of incoming requests to a predefined value based on attributes within the traffic flow.

Here are some reasons why you may want to implement Rate limits

To prevent malicious activity such as DDoS attacks.
To prevent applications and its resources (such as a database) from getting overloaded.
To create API limits based on user entitlements.

Envoy Gateway supports two types of rate limiting: Global rate limiting and Local rate limiting.

Local rate limiting applies rate limits to the traffic flowing through a single instance of Envoy proxy. This means that if the data plane has 2 replicas of Envoy running, and the rate limit is 10 requests/second, each replica will allow 10 requests/second. This is in contrast to Global Rate Limiting which applies rate limits to the traffic flowing through all instances of Envoy proxy.

Envoy Gateway introduces a new CRD called BackendTrafficPolicy that allows the user to describe their rate limit intent. This instantiated resource can be linked to a Gateway, HTTPRoute or GRPCRoute resource.

Note: Limit is applied per route. Even if a BackendTrafficPolicy targets a gateway, each route in that gateway still has a separate rate limit bucket. For example, if a gateway has 2 routes, and the limit is 100r/s, then each route has its own 100r/s rate limit bucket.

Prerequisites

Install Envoy Gateway

Follow the steps from the Quickstart to install Envoy Gateway and the HTTPRoute example manifest. Before proceeding, you should be able to query the example backend using HTTP.

Rate Limit Specific User

Here is an example of a rate limit implemented by the application developer to limit a specific user by matching on a custom x-user-id header with a value set to one.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: BackendTrafficPolicy 
metadata:
  name: policy-httproute
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: http-ratelimit
    namespace: default
  rateLimit:
    type: Local
    local:
      rules:
      - clientSelectors:
        - headers:
          - name: x-user-id
            value: one
        limit:
          requests: 3
          unit: Hour
EOF

HTTPRoute

cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: http-ratelimit
spec:
  parentRefs:
  - name: eg
  hostnames:
  - ratelimit.example 
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /
    backendRefs:
    - group: ""
      kind: Service
      name: backend
      port: 3000
EOF

The HTTPRoute status should indicate that it has been accepted and is bound to the example Gateway.

kubectl get httproute/http-ratelimit -o yaml

Get the Gateway’s address:

export GATEWAY_HOST=$(kubectl get gateway/eg -o jsonpath='{.status.addresses[0].value}')

Let’s query ratelimit.example/get 4 times. We should receive a 200 response from the example Gateway for the first 3 requests and then receive a 429 status code for the 4th request since the limit is set at 3 requests/Hour for the request which contains the header x-user-id and value one.

for i in {1..4}; do curl -I --header "Host: ratelimit.example" --header "x-user-id: one" http://${GATEWAY_HOST}/get ; sleep 1; done

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:33:31 GMT
content-length: 460
x-envoy-upstream-service-time: 4
server: envoy

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:33:32 GMT
content-length: 460
x-envoy-upstream-service-time: 2
server: envoy

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:33:33 GMT
content-length: 460
x-envoy-upstream-service-time: 0
server: envoy

HTTP/1.1 429 Too Many Requests
x-envoy-ratelimited: true
date: Wed, 08 Feb 2023 02:33:34 GMT
server: envoy
transfer-encoding: chunked

You should be able to send requests with the x-user-id header and a different value and receive successful responses from the server.

for i in {1..4}; do curl -I --header "Host: ratelimit.example" --header "x-user-id: two" http://${GATEWAY_HOST}/get ; sleep 1; done

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:34:36 GMT
content-length: 460
x-envoy-upstream-service-time: 0
server: envoy

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:34:37 GMT
content-length: 460
x-envoy-upstream-service-time: 0
server: envoy

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:34:38 GMT
content-length: 460
x-envoy-upstream-service-time: 0
server: envoy

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:34:39 GMT
content-length: 460
x-envoy-upstream-service-time: 0
server: envoy

Rate Limit All Requests

This example shows you how to rate limit all requests matching the HTTPRoute rule at 3 requests/Hour by leaving the clientSelectors field unset.

cat <<EOF | kubectl apply -f -
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: BackendTrafficPolicy 
metadata:
  name: policy-httproute
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: http-ratelimit
    namespace: default
  rateLimit:
    type: Local
    local:
      rules:
      - limit:
          requests: 3
          unit: Hour
EOF

HTTPRoute

cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: http-ratelimit
spec:
  parentRefs:
  - name: eg
  hostnames:
  - ratelimit.example 
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /
    backendRefs:
    - group: ""
      kind: Service
      name: backend
      port: 3000
EOF

for i in {1..4}; do curl -I --header "Host: ratelimit.example" http://${GATEWAY_HOST}/get ; sleep 1; done

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:33:31 GMT
content-length: 460
x-envoy-upstream-service-time: 4
server: envoy

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:33:32 GMT
content-length: 460
x-envoy-upstream-service-time: 2
server: envoy

HTTP/1.1 200 OK
content-type: application/json
x-content-type-options: nosniff
date: Wed, 08 Feb 2023 02:33:33 GMT
content-length: 460
x-envoy-upstream-service-time: 0
server: envoy

HTTP/1.1 429 Too Many Requests
x-envoy-ratelimited: true
date: Wed, 08 Feb 2023 02:33:34 GMT
server: envoy
transfer-encoding: chunked

Note: Local rate limiting does not support distinct matching. If you want to rate limit based on distinct values, you should use Global Rate Limiting.

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Last modified November 21, 2024: docs: fix wrong description on ALSEnvoyProxyAccessLog (#4751) (2def6a4)