Local rate limit¶
Local rate limiting architecture overview
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 tokens available, a 429 response is returned (the response is configurable). The local rate limit filter then sets the x-envoy-ratelimited response header. Additional response headers can be configured to be returned.
Request headers can be configured to be added to forwarded requests to the upstream when the local rate limit filter is enabled but not enforced.
Depending on the value of the config local_rate_limit_per_downstream_connection, the token bucket is either shared across all workers or on a per connection basis. This results in the local rate limits being applied either per Envoy process or per downstream connection. By default the rate limits are applied per Envoy process.
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'
local_rate_limit_per_downstream_connection: false
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.
Using rate limit descriptors for local rate limiting¶
Rate limit descriptors can be used to override local per-route rate limiting. A route’s rate limit action is used to match up a local descriptor in the filter config descriptor list. The local descriptor’s token bucket settings are then used to decide if the request should be rate limited or not depending on whether the local descriptor’s entries match the route’s rate limit actions descriptor entries. If there is no matching descriptor entries, the default token bucket is used.
Example filter configuration using descriptors:
route_config:
name: local_route
virtual_hosts:
- name: local_service
domains: ["*"]
routes:
- match: { prefix: "/foo" }
route:
cluster: service_protected_by_rate_limit
rate_limits:
- actions: # any actions in here
- request_headers:
header_name: x-envoy-downstream-service-cluster
descriptor_key: client_cluster
- request_headers:
header_name: ":path"
descriptor_key: path
typed_per_filter_config:
envoy.filters.http.local_ratelimit:
"@type": type.googleapis.com/envoy.extensions.filters.http.local_ratelimit.v3.LocalRateLimit
stat_prefix: test
token_bucket:
max_tokens: 1000
tokens_per_fill: 1000
fill_interval: 60s
filter_enabled:
runtime_key: test_enabled
default_value:
numerator: 100
denominator: HUNDRED
filter_enforced:
runtime_key: test_enforced
default_value:
numerator: 100
denominator: HUNDRED
response_headers_to_add:
- append: false
header:
key: x-test-rate-limit
value: 'true'
descriptors:
- entries:
- key: client_cluster
value: foo
- key: path
value: /foo/bar
token_bucket:
max_tokens: 10
tokens_per_fill: 10
fill_interval: 60s
- entries:
- key: client_cluster
value: foo
- key: path
value: /foo/bar2
token_bucket:
max_tokens: 100
tokens_per_fill: 100
fill_interval: 60s
- match: { prefix: "/" }
route: { cluster: default_service }
In this example, requests are rate-limited for routes prefixed with “/foo” as follow. If requests come from a downstream service cluster “foo” for “/foo/bar” path, then 10 req/min are allowed. But if they come from a downstream service cluster “foo” for “/foo/bar2” path, then 100 req/min are allowed. Otherwise, 1000 req/min are allowed.
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.