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Signed-off-by: Takeshi Yoneda <[email protected]>

api/envoy/extensions/filters/http/ratelimit/v3/rate_limit.proto

@@ -139,6 +139,11 @@ message RateLimit {
   // This is useful when the rate limit budget needs to reflect the response context that is not available
   // on the request path.
   //
+  // On the stream completion, the filter will reuse the exact same descriptors matched during the request path.
+  // In other words, the descriptors are not recalculated on the stream completion, but the rate limit requests
+  // are sent with the same descriptors as the original request sent during the request path.
+  // For example, request header matching descriptors are available on the stream completion.
+  //
   // For example, let's say the upstream service calculates the usage statistics, returns them in the response body
   // and we want to utilize these numbers to apply the rate limit action for the subsequent requests.
   // Combined with another filter that can set ``envoy.ratelimit.hits_addend`` based on the response (e.g. Lua filter),

source/extensions/filters/http/ratelimit/ratelimit.cc

@@ -88,7 +88,6 @@ void Filter::initiateCall(const Http::RequestHeaderMap& headers) {
 
 void Filter::makeRateLimitRequest() {
   if (!descriptors_.empty()) {
-    // TODO: Make addend configirable via substituion command.
     const StreamInfo::UInt32Accessor* hits_addend_filter_state =
         callbacks_->streamInfo().filterState()->getDataReadOnly<StreamInfo::UInt32Accessor>(
             HitsAddendFilterStateKey);