http: introduce addEncodedMetadata()

include/envoy/http/filter.h

@@ -609,6 +609,13 @@ class StreamEncoderFilterCallbacks : public virtual StreamFilterCallbacks {
    */
   virtual HeaderMap& addEncodedTrailers() PURE;
 
+  /**
+   * Adds new metadata to be encoded.
+   *
+   * @param metadata_map supplies the unique_ptr of the metadata to be encoded.
+   */
+  virtual void addEncodedMetadata(MetadataMapPtr&& metadata_map) PURE;
+
   /**
    * Called when an encoder filter goes over its high watermark.
    */

source/common/http/conn_manager_impl.cc

@@ -1309,6 +1309,7 @@ void ConnectionManagerImpl::ActiveStream::encodeHeaders(ActiveStreamEncoderFilte
     ENVOY_STREAM_LOG(trace, "encode headers called: filter={} status={}", *this,
                      static_cast<const void*>((*entry).get()), static_cast<uint64_t>(status));
 
+    (*entry)->encode_headers_called_ = true;
     const auto continue_iteration =
         (*entry)->commonHandleAfterHeadersCallback(status, encoding_headers_only_);
 
@@ -1438,10 +1439,19 @@ void ConnectionManagerImpl::ActiveStream::encodeMetadata(ActiveStreamEncoderFilt
                                                          MetadataMapPtr&& metadata_map_ptr) {
   resetIdleTimer();
 
-  // Metadata currently go through all filters.
-  ASSERT(filter == nullptr);
-  std::list<ActiveStreamEncoderFilterPtr>::iterator entry = encoder_filters_.begin();
+  std::list<ActiveStreamEncoderFilterPtr>::iterator entry =
+      commonEncodePrefix(filter, false, FilterIterationStartState::CanStartFromCurrent);
+
   for (; entry != encoder_filters_.end(); entry++) {
+    // If the filter pointed by entry has stopped for all frame type, stores metadata and returns.
+    // If the filter pointed by entry hasn't returned from encodeHeaders, stores newly added
+    // metadata in case encodeHeaders returns StopAllIteration. The latter can happen when headers
+    // callbacks generate new metadata.
+    if (!(*entry)->encode_headers_called_ || (*entry)->stoppedAll()) {
+      (*entry)->getSavedResponseMetadata()->emplace_back(std::move(metadata_map_ptr));
+      return;
+    }
+
     FilterMetadataStatus status = (*entry)->handle_->encodeMetadata(*metadata_map_ptr);
     ENVOY_STREAM_LOG(trace, "encode metadata called: filter={} status={}", *this,
                      static_cast<const void*>((*entry).get()), static_cast<uint64_t>(status));
@@ -2086,6 +2096,19 @@ Buffer::WatermarkBufferPtr ConnectionManagerImpl::ActiveStreamEncoderFilter::cre
   return Buffer::WatermarkBufferPtr{buffer};
 }
 
+void ConnectionManagerImpl::ActiveStreamEncoderFilter::handleMetadataAfterHeadersCallback() {
+  // If we drain accumulated metadata, the iteration must start with the current filter.
+  const bool saved_state = iterate_from_current_filter_;
+  iterate_from_current_filter_ = true;
+  // If encodeHeaders() returns StopAllIteration, we should skip draining metadata, and wait
+  // for doMetadata() to drain the metadata after iteration continues.
+  if (!stoppedAll() && saved_response_metadata_ != nullptr &&
+      !getSavedResponseMetadata()->empty()) {
+    drainSavedResponseMetadata();
+  }
+  // Restores the original value of iterate_from_current_filter_.
+  iterate_from_current_filter_ = saved_state;
+}
 void ConnectionManagerImpl::ActiveStreamEncoderFilter::addEncodedData(Buffer::Instance& data,
                                                                       bool streaming) {
   return parent_.addEncodedData(*this, data, streaming);
@@ -2101,6 +2124,11 @@ HeaderMap& ConnectionManagerImpl::ActiveStreamEncoderFilter::addEncodedTrailers(
   return parent_.addEncodedTrailers();
 }
 
+void ConnectionManagerImpl::ActiveStreamEncoderFilter::addEncodedMetadata(
+    MetadataMapPtr&& metadata_map_ptr) {
+  return parent_.encodeMetadata(this, std::move(metadata_map_ptr));
+}
+
 void ConnectionManagerImpl::ActiveStreamEncoderFilter::
     onEncoderFilterAboveWriteBufferHighWatermark() {
   ENVOY_STREAM_LOG(debug, "Disabling upstream stream due to filter callbacks.", parent_);

source/common/http/conn_manager_impl.h

@@ -101,7 +101,7 @@ class ConnectionManagerImpl : Logger::Loggable<Logger::Id::http>,
         : parent_(parent), iteration_state_(IterationState::Continue),
           iterate_from_current_filter_(false), headers_continued_(false),
           continue_headers_continued_(false), end_stream_(false), dual_filter_(dual_filter),
-          decode_headers_called_(false) {}
+          decode_headers_called_(false), encode_headers_called_(false) {}
 
     // Functions in the following block are called after the filter finishes processing
     // corresponding data. Those functions handle state updates and data storage (if needed)
@@ -131,7 +131,7 @@ class ConnectionManagerImpl : Logger::Loggable<Logger::Id::http>,
     virtual const HeaderMapPtr& trailers() PURE;
     virtual void doMetadata() PURE;
     // TODO(soya3129): make this pure when adding impl to encodefilter.
-    virtual void handleMetadataAfterHeadersCallback() {}
+    virtual void handleMetadataAfterHeadersCallback() PURE;
 
     // Http::StreamFilterCallbacks
     const Network::Connection* connection() override;
@@ -173,8 +173,8 @@ class ConnectionManagerImpl : Logger::Loggable<Logger::Id::http>,
     // either because [de|en]codeHeaders() of the current filter returns StopAllIteration or because
     // [de|en]codeHeaders() adds new metadata to [de|en]code, but we don't know
     // [de|en]codeHeaders()'s return value yet. The storage is created on demand.
-    std::unique_ptr<MetadataMapVector> saved_request_metadata_;
-    std::unique_ptr<MetadataMapVector> saved_response_metadata_;
+    std::unique_ptr<MetadataMapVector> saved_request_metadata_{nullptr};
+    std::unique_ptr<MetadataMapVector> saved_response_metadata_{nullptr};
     // The state of iteration.
     enum class IterationState {
       Continue,            // Iteration has not stopped for any frame type.
@@ -197,6 +197,7 @@ class ConnectionManagerImpl : Logger::Loggable<Logger::Id::http>,
     bool end_stream_ : 1;
     const bool dual_filter_ : 1;
     bool decode_headers_called_ : 1;
+    bool encode_headers_called_ : 1;
   };
 
   /**
@@ -346,6 +347,7 @@ class ConnectionManagerImpl : Logger::Loggable<Logger::Id::http>,
       }
       getSavedResponseMetadata()->clear();
     }
+    void handleMetadataAfterHeadersCallback() override;
 
     void doMetadata() override {
       if (saved_response_metadata_ != nullptr) {
@@ -359,6 +361,7 @@ class ConnectionManagerImpl : Logger::Loggable<Logger::Id::http>,
     void addEncodedData(Buffer::Instance& data, bool streaming) override;
     void injectEncodedDataToFilterChain(Buffer::Instance& data, bool end_stream) override;
     HeaderMap& addEncodedTrailers() override;
+    void addEncodedMetadata(MetadataMapPtr&& metadata_map) override;
     void onEncoderFilterAboveWriteBufferHighWatermark() override;
     void onEncoderFilterBelowWriteBufferLowWatermark() override;
     void setEncoderBufferLimit(uint32_t limit) override { parent_.setBufferLimit(limit); }

source/docs/h2_metadata.md

@@ -85,19 +85,16 @@ StreamDecoderFilter::decodeMetadata(MetadataMap metadata\_map). New metadata can
 be added directly to metadata\_map.
 
 If users need to add new metadata for a response to downstream, a
-StreamFilter should be created. Users pass the metadata to be added to
-StreamDecoderFilterCallbacks::encodeMetadata(MetadataMapPtr&&
+StreamEncoderFilter should be created. Users pass the metadata to be added to
+StreamEncoderFilterCallbacks::addEncodedMetadata(MetadataMapPtr&&
 metadata\_map\_ptr). This function can be called in
-StreamFilter::encode100ContinueHeaders(HeaderMap& headers), StreamFilter::encodeHeaders(HeaderMap& headers, bool end\_stream),
-StreamFilter::encodeData(Buffer::Instance& data, bool end\_stream), StreamFilter::encodeTrailers(HeaderMap& trailers).
-Consequently, the new metadata will be passed through all the encoding filters. Note that, the added
-metadata should not share the same key as the metadata to be consumed. Otherwise, the added metadata
-will be consumed.
+StreamEncoderFilter::encode100ContinueHeaders(HeaderMap& headers), StreamEncoderFilter::encodeHeaders(HeaderMap& headers, bool end\_stream),
+StreamEncoderFilter::encodeData(Buffer::Instance& data, bool end\_stream), StreamEncoderFilter::encodeTrailers(HeaderMap& trailers).
+Consequently, the new metadata will be passed through all the encoding filters that follow the filter
+where the new metadata are added.
 
 If users receive metadata from upstream, new metadata can be added directly to
-the input argument metadata\_map in StreamFilter::encodeMetadata(MetadataMap& metadata\_map). Note that,
-users should never call StreamDecoderFilterCallbacks::encodeMetadata(MetadataMapPtr&&
-metadata\_map\_ptr) to add new metadata in StreamFilter::encodeMetadata(MetadataMap& metadata\_map).
+the input argument metadata\_map in StreamFilter::encodeMetadata(MetadataMap& metadata\_map).
 
 ### Metadata implementation
 

test/common/http/http1/BUILD

@@ -27,6 +27,7 @@ envoy_cc_test(
         "//test/mocks/protobuf:protobuf_mocks",
         "//test/mocks/thread_local:thread_local_mocks",
         "//test/mocks/upstream:upstream_mocks",
+        "//test/test_common:logging_lib",
     ],
 )
 

test/common/http/http1/codec_impl_test.cc

@@ -18,6 +18,7 @@
 #include "test/mocks/protobuf/mocks.h"
 #include "test/mocks/runtime/mocks.h"
 #include "test/mocks/thread_local/mocks.h"
+#include "test/test_common/logging.h"
 #include "test/test_common/printers.h"
 #include "test/test_common/utility.h"
 

test/integration/filters/encode_headers_return_stop_all_filter.cc

@@ -35,6 +35,10 @@ class EncodeHeadersReturnStopAllFilter : public Http::PassThroughFilter {
 
     createTimerForContinue();
 
+    Http::MetadataMap metadata_map = {{"headers", "headers"}};
+    Http::MetadataMapPtr metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
+
     Http::HeaderEntry* entry_buffer = header_map.get(Envoy::Http::LowerCaseString("buffer_limit"));
     if (entry_buffer == nullptr) {
       return Http::FilterHeadersStatus::StopAllIterationAndBuffer;
@@ -56,13 +60,21 @@ class EncodeHeadersReturnStopAllFilter : public Http::PassThroughFilter {
       // encodeData will only be called once after iteration resumes.
       EXPECT_EQ(data.length(), content_size_);
     }
+    Http::MetadataMap metadata_map = {{"data", "data"}};
+    Http::MetadataMapPtr metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
+
     Buffer::OwnedImpl added_data(std::string(added_size_, 'a'));
     encoder_callbacks_->addEncodedData(added_data, false);
     return Http::FilterDataStatus::Continue;
   }
 
   Http::FilterTrailersStatus encodeTrailers(Http::HeaderMap&) override {
     ASSERT(timer_triggered_);
+    Http::MetadataMap metadata_map = {{"trailers", "trailers"}};
+    Http::MetadataMapPtr metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
+
     Buffer::OwnedImpl data(std::string(added_size_, 'a'));
     encoder_callbacks_->addEncodedData(data, false);
     return Http::FilterTrailersStatus::Continue;

test/integration/filters/response_metadata_filter.cc

@@ -16,42 +16,39 @@ class ResponseMetadataStreamFilter : public Http::PassThroughFilter {
 public:
   // Inserts one new metadata_map.
   Http::FilterHeadersStatus encodeHeaders(Http::HeaderMap&, bool) override {
-    Http::MetadataMap metadata_map = {
-        {"headers", "headers"}, {"duplicate", "duplicate"}, {"remove", "remove"}};
+    Http::MetadataMap metadata_map = {{"headers", "headers"}, {"duplicate", "duplicate"}};
     Http::MetadataMapPtr metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
-    decoder_callbacks_->encodeMetadata(std::move(metadata_map_ptr));
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
     return Http::FilterHeadersStatus::Continue;
   }
 
   // Inserts one new metadata_map.
   Http::FilterDataStatus encodeData(Buffer::Instance&, bool) override {
-    Http::MetadataMap metadata_map = {
-        {"data", "data"}, {"duplicate", "duplicate"}, {"remove", "remove"}};
+    Http::MetadataMap metadata_map = {{"data", "data"}, {"duplicate", "duplicate"}};
     Http::MetadataMapPtr metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
-    decoder_callbacks_->encodeMetadata(std::move(metadata_map_ptr));
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
     return Http::FilterDataStatus::Continue;
   }
 
   // Inserts two metadata_maps by calling decoder_callbacks_->encodeMetadata() twice.
   Http::FilterTrailersStatus encodeTrailers(Http::HeaderMap&) override {
-    Http::MetadataMap metadata_map = {{"trailers", "trailers"}, {"remove", "remove"}};
+    Http::MetadataMap metadata_map = {{"trailers", "trailers"}};
     Http::MetadataMapPtr metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
-    decoder_callbacks_->encodeMetadata(std::move(metadata_map_ptr));
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
     metadata_map = {{"duplicate", "duplicate"}};
     metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
-    decoder_callbacks_->encodeMetadata(std::move(metadata_map_ptr));
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
     return Http::FilterTrailersStatus::Continue;
   }
 
   // Inserts two metadata_maps by calling decoder_callbacks_->encodeMetadata() twice.
   Http::FilterHeadersStatus encode100ContinueHeaders(Http::HeaderMap&) override {
-    Http::MetadataMap metadata_map = {
-        {"100-continue", "100-continue"}, {"duplicate", "duplicate"}, {"remove", "remove"}};
+    Http::MetadataMap metadata_map = {{"100-continue", "100-continue"}, {"duplicate", "duplicate"}};
     Http::MetadataMapPtr metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
-    decoder_callbacks_->encodeMetadata(std::move(metadata_map_ptr));
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
     metadata_map = {{"duplicate", "duplicate"}};
     metadata_map_ptr = std::make_unique<Http::MetadataMap>(metadata_map);
-    decoder_callbacks_->encodeMetadata(std::move(metadata_map_ptr));
+    encoder_callbacks_->addEncodedMetadata(std::move(metadata_map_ptr));
     return Http::FilterHeadersStatus::Continue;
   }
 
@@ -66,10 +63,6 @@ class ResponseMetadataStreamFilter : public Http::PassThroughFilter {
       metadata_map.erase("consume");
       metadata_map.emplace("replace", "replace");
     }
-    it = metadata_map.find("remove");
-    if (it != metadata_map.end()) {
-      metadata_map.erase("remove");
-    }
     it = metadata_map.find("metadata");
     if (it != metadata_map.end()) {
       metadata_map.erase("metadata");