Enabling Rate Limits using Envoy

This task shows you how to use Envoy’s native rate limiting to dynamically limit the traffic to an Istio service. In this task, you will apply a global rate-limit for the productpage service through ingress gateway that allows 1 requests per minute across all instances of the service. Additionally, you will apply a local rate-limit for each individual productpage instance that will allow 10 requests per minute. In this way, you will ensure that the productpage service handles a maximum of 1 requests per minute through instance gateway, but each productpage instance can handle up to 10 requests per minute, allowing for any in-mesh traffic.

Before you begin

  1. Setup Istio in a Kubernetes cluster by following the instructions in the Installation Guide.

  2. Deploy the Bookinfo sample application.

Rate limits

Envoy supports two kinds of rate limiting: global and local. Global rate limiting uses a global gRPC rate limiting service to provide rate limiting for the entire mesh. Local rate limiting is used to limit the rate of requests per service instance. Local rate limiting can be used in conjunction with global rate limiting to reduce load on the global rate limiting service.

In this task you will configure Envoy to rate limit traffic to a specific path of a service using both global and local rate limits.

Global rate limit

Envoy can be used to set up global rate limits for your mesh. Global rate limiting in Envoy uses a gRPC API for requesting quota from a rate limiting service. A reference implementation of the API, written in Go with a Redis backend, is used below.

  1. Use the following configmap to configure the reference implementation to rate limit requests to the path /productpage at 1 req/min and all other requests at 100 req/min.

    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: ratelimit-config
    data:
      config.yaml: |
        domain: productpage-ratelimit
        descriptors:
          - key: PATH
            value: "/productpage"
            rate_limit:
              unit: minute
              requests_per_unit: 1
          - key: PATH
            rate_limit:
              unit: minute
              requests_per_unit: 100
    
  2. Create a global rate limit service which implements Envoy’s rate limit service protocol. As a reference, a demo configuration can be found here, which is based on a reference implementation provided by Envoy.

  3. Apply an EnvoyFilter to the ingressgateway to enable global rate limiting using Envoy’s global rate limit filter.

    The first patch inserts the envoy.filters.http.ratelimit global envoy filter filter into the HTTP_FILTER chain. The rate_limit_service field specifies the external rate limit service, rate_limit_cluster in this case.

    The second patch defines the rate_limit_cluster, which provides the endpoint location of the external rate limit service.

    $ kubectl apply -f - <<EOF
    apiVersion: networking.istio.io/v1alpha3
    kind: EnvoyFilter
    metadata:
      name: filter-ratelimit
      namespace: istio-system
    spec:
      workloadSelector:
        # select by label in the same namespace
        labels:
          istio: ingressgateway
      configPatches:
        # The Envoy config you want to modify
        - applyTo: HTTP_FILTER
          match:
            context: GATEWAY
            listener:
              filterChain:
                filter:
                  name: "envoy.http_connection_manager"
                  subFilter:
                    name: "envoy.router"
          patch:
            operation: INSERT_BEFORE
            # Adds the Envoy Rate Limit Filter in HTTP filter chain.
            value:
              name: envoy.filters.http.ratelimit
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.http.ratelimit.v3.RateLimit
                # domain can be anything! Match it to the ratelimter service config
                domain: productpage-ratelimit
                failure_mode_deny: true
                rate_limit_service:
                  grpc_service:
                    envoy_grpc:
                      cluster_name: rate_limit_cluster
                    timeout: 10s
                  transport_api_version: V3
        - applyTo: CLUSTER
          match:
            cluster:
              service: ratelimit.default.svc.cluster.local
          patch:
            operation: ADD
            # Adds the rate limit service cluster for rate limit service defined in step 1.
            value:
              name: rate_limit_cluster
              type: STRICT_DNS
              connect_timeout: 10s
              lb_policy: ROUND_ROBIN
              http2_protocol_options: {}
              load_assignment:
                cluster_name: rate_limit_cluster
                endpoints:
                - lb_endpoints:
                  - endpoint:
                      address:
                         socket_address:
                          address: ratelimit.default.svc.cluster.local
                          port_value: 8081
    EOF
    
  4. Apply another EnvoyFilter to the ingressgateway that defines the route configuration on which to rate limit. This adds rate limit actions for any route from a virtual host named *.80.

    $ kubectl apply -f - <<EOF
    apiVersion: networking.istio.io/v1alpha3
    kind: EnvoyFilter
    metadata:
      name: filter-ratelimit-svc
      namespace: istio-system
    spec:
      workloadSelector:
        labels:
          istio: ingressgateway
      configPatches:
        - applyTo: VIRTUAL_HOST
          match:
            context: GATEWAY
            routeConfiguration:
              vhost:
                name: "*:80"
                route:
                  action: ANY
          patch:
            operation: MERGE
            # Applies the rate limit rules.
            value:
              rate_limits:
                - actions: # any actions in here
                  - request_headers:
                      header_name: ":path"
                      descriptor_key: "PATH"
    EOF
    

Local rate limit

Envoy supports local rate limiting of L4 connections and HTTP requests. This allows you to apply rate limits at the instance level, in the proxy itself, without calling any other service.

The following EnvoyFilter enables local rate limiting for any traffic through the productpage service. The HTTP_FILTER patch inserts the envoy.filters.http.local_ratelimit local envoy filter into the HTTP connection manager filter chain. The local rate limit filter’s token bucket is configured to allow 10 requests/min. The filter is also configured to add an x-local-rate-limit response header to requests that are blocked.

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: filter-local-ratelimit-svc
  namespace: istio-system
spec:
  workloadSelector:
    labels:
      app: productpage
  configPatches:
    - applyTo: HTTP_FILTER
      listener:
        filterChain:
          filter:
            name: "envoy.http_connection_manager"
      patch:
        operation: INSERT_BEFORE
        value:
          name: envoy.filters.http.local_ratelimit
          typed_config:
            "@type": type.googleapis.com/udpa.type.v1.TypedStruct
            type_url: type.googleapis.com/envoy.extensions.filters.http.local_ratelimit.v3.LocalRateLimit
            value:
              stat_prefix: http_local_rate_limiter
              token_bucket:
                max_tokens: 10
                tokens_per_fill: 10
                fill_interval: 60s
              filter_enabled:
                runtime_key: local_rate_limit_enabled
                default_value:
                  numerator: 100
                  denominator: HUNDRED
              filter_enforced:
                runtime_key: local_rate_limit_enforced
                default_value:
                  numerator: 100
                  denominator: HUNDRED
              response_headers_to_add:
                - append: false
                  header:
                    key: x-local-rate-limit
                    value: 'true'
EOF

The above configuration applies local rate limiting to all vhosts/routes. Alternatively, you can restrict it to a specific route.

The following EnvoyFilter enables local rate limiting for any traffic to port 80 of the productpage service. Unlike the previous configuration, there is no token_bucket included in the HTTP_FILTER patch. The token_bucket is instead defined in the second (HTTP_ROUTE) patch which includes a typed_per_filter_config for the envoy.filters.http.local_ratelimit local envoy filter, for routes to virtual host inbound|http|9080.

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: filter-local-ratelimit-svc
  namespace: istio-system
spec:
  workloadSelector:
    labels:
      app: productpage
  configPatches:
    - applyTo: HTTP_FILTER
      listener:
        filterChain:
          filter:
            name: "envoy.http_connection_manager"
      patch:
        operation: INSERT_BEFORE
        value:
          name: envoy.filters.http.local_ratelimit
          typed_config:
            "@type": type.googleapis.com/udpa.type.v1.TypedStruct
            type_url: type.googleapis.com/envoy.extensions.filters.http.local_ratelimit.v3.LocalRateLimit
            value:
              stat_prefix: http_local_rate_limiter
    - applyTo: HTTP_ROUTE
      match:
        context: SIDECAR_OUTBOUND
        routeConfiguration:
          vhost:
            name: "inbound|http|9080"
            route:
              action: ANY
      patch:
        operation: MERGE
        value:
          typed_per_filter_config:
            envoy.filters.http.local_ratelimit:
              "@type": type.googleapis.com/udpa.type.v1.TypedStruct
              type_url: type.googleapis.com/envoy.extensions.filters.http.local_ratelimit.v3.LocalRateLimit
              value:
                stat_prefix: http_local_rate_limiter
                token_bucket:
                  max_tokens: 10
                  tokens_per_fill: 10
                  fill_interval: 60s
                filter_enabled:
                  runtime_key: local_rate_limit_enabled
                  default_value:
                    numerator: 100
                    denominator: HUNDRED
                filter_enforced:
                  runtime_key: local_rate_limit_enforced
                  default_value:
                    numerator: 100
                    denominator: HUNDRED
                response_headers_to_add:
                  - append: false
                    header:
                      key: x-local-rate-limit
                      value: 'true'
EOF

Verify the results

Verify global rate limit

Send traffic to the Bookinfo sample. Visit http://$GATEWAY_URL/productpage in your web browser or issue the following command:

$ curl "http://$GATEWAY_URL/productpage"

You will see the first request go through but every following request within a minute will get a 429 response.

Verify local rate limit

Although the global rate limit at the ingress gateway limits requests to the productpage service at 1 req/min, the local rate limit for productpage instances allows 10 req/min. To confirm this, send internal productpage requests, from the ratings pod, using the following curl command:

$ kubectl exec "$(kubectl get pod -l app=ratings -o jsonpath='{.items[0].metadata.name}')" -c ratings -- curl -sS productpage:9080/productpage | grep -o "<title>.*</title>"
<title>Simple Bookstore App</title>

You should see no more than 10 req/min go through per productpage instance.