Global rate limit is not accurate: 10 limit tps, but can reach 30 tps

[datavisorhenryzhao]

When I using ingress-nginx controller on k8s, and enable global rate limit. But find that the limit tps does not work well.

ingress-nginx controller cm

global-rate-limit-memcached-connect-timeout:50ms
global-rate-limit-memcached-host:memcached.ingress-nginx.svc.cluster.local
global-rate-limit-memcached-max-idle-timeout:50ms
global-rate-limit-memcached-pool-size: "10000"
global-rate-limit-memcached-port:"11211"

app ingress

apiVersion: v1
items:
- apiVersion: networking.k8s.io/v1
  kind: Ingress
  metadata:
    annotations:
      nginx.ingress.kubernetes.io/global-rate-limit: "10"
      nginx.ingress.kubernetes.io/global-rate-limit-key: $request_uri
      nginx.ingress.kubernetes.io/global-rate-limit-window: 1s
    creationTimestamp: "2024-01-18T02:29:56Z"
    generation: 1
    name: demo-localhost
    namespace: henry-test
    resourceVersion: "28783032"
    uid: fd40379e-f635-4533-90bc-0f4b56ce7430
  spec:
    ingressClassName: nginx
    rules:
    - host: demo.localdev.me
      http:
        paths:
        - backend:
            service:
              name: demo
              port:
                number: 80
          path: /
          pathType: Prefix
  status:
    loadBalancer:
      ingress:
      - ip: 3.239.19.65
kind: List
metadata:
  resourceVersion: ""

Using wrk test

After modifying code, it looks better