Rate limiting with Kong Ingress Controller

To add rate limiting to the echo Service, create a new Rate Limiting KongPlugin:

echo "
apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: rate-limit-5-min
  namespace: kong
  annotations:
    kubernetes.io/ingress.class: kong
plugin: rate-limiting
config:
  minute: 5
  policy: local
" | kubectl apply -f -

Next, apply the KongPlugin resource by annotating the service resource:

kubectl annotate -n kong service echo konghq.com/plugins=rate-limit-5-min

Send repeated requests to decrement the remaining limit headers, and block requests after the fifth request:

for _ in {1..6}; do
  curl  -i $PROXY_IP/echo  
  echo
done

for _ in {1..6}; do
  curl  -i $PROXY_IP/echo  
  echo
done

The policy: local setting in the plugin configuration tracks request counters in each Pod’s local memory separately. Counters are not synchronized across Pods, so clients can send requests past the limit without being throttled if they route through different Pods.

To test this, scale your Deployment to three replicas:

kubectl scale --replicas 3 -n kong deployment kong-gateway

It may take up to 30 seconds for the new replicas to come online. Run kubectl get pods -n kong and check the Ready column to validate that the replicas are online

Sending requests to this Service does not reliably decrement the remaining counter:

for _ in {1..10}; do
  curl  -sv $PROXY_IP/echo  2>&1 | grep -E "(< RateLimit-Remaining)"
  echo
done

< RateLimit-Remaining: 4

< RateLimit-Remaining: 4

< RateLimit-Remaining: 3

< RateLimit-Remaining: 4

< RateLimit-Remaining: 3

< RateLimit-Remaining: 2

< RateLimit-Remaining: 3

< RateLimit-Remaining: 2

< RateLimit-Remaining: 1

< RateLimit-Remaining: 1

for _ in {1..10}; do
  curl  -sv $PROXY_IP/echo  2>&1 | grep -E "(< RateLimit-Remaining)"
  echo
done

< RateLimit-Remaining: 4

< RateLimit-Remaining: 4

< RateLimit-Remaining: 3

< RateLimit-Remaining: 4

< RateLimit-Remaining: 3

< RateLimit-Remaining: 2

< RateLimit-Remaining: 3

< RateLimit-Remaining: 2

< RateLimit-Remaining: 1

< RateLimit-Remaining: 1

Using a load balancer that distributes client requests to the same Pod can alleviate this somewhat, but changes to the number of replicas can still disrupt accurate accounting. To consistently enforce the limit, the plugin needs to use a shared set of counters across all Pods. The redis policy can do this when a Redis instance is available.

Redis provides an external database for Kong Gateway components to store shared data, such as rate limiting counters. There are several options to install it.

Bitnami provides a Helm chart for Redis with turnkey options for authentication.

1. Create a password Secret and replace PASSWORD with a password of your choice.

   kubectl create -n kong secret generic redis-password-secret --from-literal=redis-password=PASSWORD
   

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2. Install Redis

    helm install -n kong redis oci://registry-1.docker.io/bitnamicharts/redis \
      --set auth.existingSecret=redis-password-secret \
      --set architecture=standalone
   

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   Helm displays the instructions that describes the new installation.

   If Redis is not accessible, Kong Gateway will allow incoming requests. Run kubectl get pods -n kong redis-master-0 and check the Ready column to ensure that Redis is ready before continuing.

3. Update your plugin configuration with the redis policy, Service, and credentials. Replace PASSWORD with the password that you set for Redis.

    kubectl patch -n kong kongplugin rate-limit-5-min --type json --patch '[
      {
        "op":"replace",
        "path":"/config/policy",
        "value":"redis"
      },
      {
        "op":"add",
        "path":"/config/redis_host",
        "value":"redis-master"
      },
      {
        "op":"add",
        "path":"/config/redis_password",
        "value":"PASSWORD"
      }
    ]'
   

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   If the redis_username is not set, it uses the default redis user.

Send the following request to test the rate limiting functionality in the multi-Pod deployment:

for _ in {1..6}; do
  curl  -sv $PROXY_IP/echo  2>&1 | grep -E "(< RateLimit-Remaining|< HTTP)"
  echo
done

< HTTP/1.1 200 OK
< RateLimit-Remaining: 4

< HTTP/1.1 200 OK
< RateLimit-Remaining: 3

< HTTP/1.1 200 OK
< RateLimit-Remaining: 2

< HTTP/1.1 200 OK
< RateLimit-Remaining: 1

< HTTP/1.1 200 OK
< RateLimit-Remaining: 0

< HTTP/1.1 429 Too Many Requests
< RateLimit-Remaining: 0

for _ in {1..6}; do
  curl  -sv $PROXY_IP/echo  2>&1 | grep -E "(< RateLimit-Remaining|< HTTP)"
  echo
done

< HTTP/1.1 200 OK
< RateLimit-Remaining: 4

< HTTP/1.1 200 OK
< RateLimit-Remaining: 3

< HTTP/1.1 200 OK
< RateLimit-Remaining: 2

< HTTP/1.1 200 OK
< RateLimit-Remaining: 1

< HTTP/1.1 200 OK
< RateLimit-Remaining: 0

< HTTP/1.1 429 Too Many Requests
< RateLimit-Remaining: 0