.. _config_http_filters_rate_limit: Rate limit ========== * Global rate limiting :ref:`architecture overview ` * :ref:`v3 API reference ` * This filter should be configured with the name *envoy.filters.http.ratelimit*. The HTTP rate limit filter will call the rate limit service when the request's route or virtual host has one or more :ref:`rate limit configurations` that match the filter stage setting. The :ref:`route` can optionally include the virtual host rate limit configurations. More than one configuration can apply to a request. Each configuration results in a descriptor being sent to the rate limit service. If the rate limit service is called, and the response for any of the descriptors is over limit, a 429 response is returned. The rate limit filter also sets the :ref:`x-envoy-ratelimited` header, unless :ref:`disable_x_envoy_ratelimited_header ` is set to true. If there is an error in calling rate limit service or rate limit service returns an error and :ref:`failure_mode_deny ` is set to true, a 500 response is returned. .. _config_http_filters_rate_limit_composing_actions: Composing Actions ----------------- Each :ref:`rate limit action ` on the route or virtual host populates a descriptor entry. A vector of descriptor entries compose a descriptor. To create more complex rate limit descriptors, actions can be composed in any order. The descriptor will be populated in the order the actions are specified in the configuration. Example 1 ^^^^^^^^^ For example, to generate the following descriptor: .. code-block:: cpp ("generic_key", "some_value") ("source_cluster", "from_cluster") The configuration would be: .. code-block:: yaml actions: - {source_cluster: {}} - {generic_key: {descriptor_value: some_value}} Example 2 ^^^^^^^^^ If an action doesn't append a descriptor entry, no descriptor is generated for the configuration. For the following configuration: .. code-block:: yaml actions: - {source_cluster: {}} - {remote_address: {}} - {generic_key: {descriptor_value: some_value}} If a request did not set :ref:`x-forwarded-for`, no descriptor is generated. If a request sets :ref:`x-forwarded-for`, the the following descriptor is generated: .. code-block:: cpp ("generic_key", "some_value") ("remote_address", "") ("source_cluster", "from_cluster") .. _config_http_filters_rate_limit_rate_limit_override: Rate Limit Override ------------------- A :ref:`rate limit action ` can optionally contain a :ref:`limit override `. The limit value will be appended to the descriptor produced by the action and sent to the ratelimit service, overriding the static service configuration. The override can be configured to be taken from the :ref:`Dynamic Metadata ` under a specified :ref: `key `. If the value is misconfigured or key does not exist, the override configuration is ignored. Example 3 ^^^^^^^^^ The following configuration .. code-block:: yaml actions: - {generic_key: {descriptor_value: some_value}} limit: metadata_key: key: test.filter.key path: - key: test .. _config_http_filters_rate_limit_override_dynamic_metadata: Will lookup the value of the dynamic metadata. The value must be a structure with integer field "requests_per_unit" and a string field "unit" which is parseable to :ref:`RateLimitUnit enum `. For example, with the following dynamic metadata the rate limit override of 42 requests per hour will be appended to the rate limit descriptor. .. code-block:: yaml test.filter.key: test: requests_per_unit: 42 unit: HOUR Descriptor extensions --------------------- Rate limit descriptors are extensible with custom descriptors. For example, :ref:`computed descriptors ` extension allows using any of the :ref:`request attributes ` as a descriptor value: .. code-block:: yaml actions: - extension: name: custom typed_config: "@type": type.googleapis.com/envoy.extensions.rate_limit_descriptors.expr.v3.Descriptor descriptor_key: my_descriptor_name text: request.method Statistics ---------- The rate limit filter outputs statistics in the *cluster..ratelimit.* namespace. 429 responses are emitted to the normal cluster :ref:`dynamic HTTP statistics `. .. csv-table:: :header: Name, Type, Description :widths: 1, 1, 2 ok, Counter, Total under limit responses from the rate limit service error, Counter, Total errors contacting the rate limit service over_limit, Counter, total over limit responses from the rate limit service failure_mode_allowed, Counter, "Total requests that were error(s) but were allowed through because of :ref:`failure_mode_deny ` set to false." Dynamic Metadata ---------------- .. _config_http_filters_ratelimit_dynamic_metadata: The ratelimit filter emits dynamic metadata as an opaque ``google.protobuf.Struct`` *only* when the gRPC ratelimit service returns a :ref:`RateLimitResponse ` with a filled :ref:`dynamic_metadata ` field. Runtime ------- The HTTP rate limit filter supports the following runtime settings: ratelimit.http_filter_enabled % of requests that will call the rate limit service. Defaults to 100. ratelimit.http_filter_enforcing % of requests that that will have the rate limit service decision enforced. Defaults to 100. This can be used to test what would happen before fully enforcing the outcome. ratelimit..http_filter_enabled % of requests that will call the rate limit service for a given *route_key* specified in the :ref:`rate limit configuration `. Defaults to 100.