Local rate limit

Local rate limit

Local rate limiting architecture overview
v3 API reference
This filter should be configured with the name envoy.filters.http.local_ratelimit.

The HTTP local rate limit filter applies a token bucket rate limit when the request’s route or virtual host has a per filter local rate limit configuration.

If the local rate limit token bucket is checked, and there are no token availables, a 429 response is returned (the response is configurable). The local rate limit filter also sets the x-envoy-ratelimited header. Additional response headers may be configured.

Example configuration

Example filter configuration for a globally set rate limiter (e.g.: all vhosts/routes share the same token bucket):

name: envoy.filters.http.local_ratelimit
typed_config:
  "@type": type.googleapis.com/envoy.extensions.filters.http.local_ratelimit.v3.LocalRateLimit
  stat_prefix: http_local_rate_limiter
  token_bucket:
    max_tokens: 10000
    tokens_per_fill: 1000
    fill_interval: 1s
  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'

Example filter configuration for a globally disabled rate limiter but enabled for a specific route:

name: envoy.filters.http.local_ratelimit
typed_config:
  "@type": type.googleapis.com/envoy.extensions.filters.http.local_ratelimit.v3.LocalRateLimit
  stat_prefix: http_local_rate_limiter

The route specific configuration:

route_config:
  name: local_route
  virtual_hosts:
  - name: local_service
    domains: ["*"]
    routes:
    - match: { prefix: "/path/with/rate/limit" }
      route: { cluster: service_protected_by_rate_limit }
      typed_per_filter_config:
        envoy.filters.http.local_ratelimit:
          "@type": type.googleapis.com/envoy.extensions.filters.http.local_ratelimit.v3.LocalRateLimit
          token_bucket:
            max_tokens: 10000
            tokens_per_fill: 1000
            fill_interval: 1s
          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'
    - match: { prefix: "/" }
      route: { cluster: default_service }

Note that if this filter is configured as globally disabled and there are no virtual host or route level token buckets, no rate limiting will be applied.

Statistics

The local rate limit filter outputs statistics in the <stat_prefix>.http_local_rate_limit. namespace. 429 responses – or the configured status code – are emitted to the normal cluster dynamic HTTP statistics.

Name	Type	Description
enabled	Counter	Total number of requests for which the rate limiter was consulted
ok	Counter	Total under limit responses from the token bucket
rate_limited	Counter	Total responses without an available token (but not necessarily enforced)
enforced	Counter	Total number of requests for which rate limiting was applied (e.g.: 429 returned)

Runtime

The HTTP rate limit filter supports the following runtime fractional settings:

http_filter_enabled

% of requests that will check the local rate limit decision, but not enforce, for a given route_key specified in the local rate limit configuration. Defaults to 0.

http_filter_enforcing

% of requests that will enforce the local rate limit decision for a given route_key specified in the local rate limit configuration. Defaults to 0. This can be used to test what would happen before fully enforcing the outcome.