Unable to access filter state from with Golang filter

[asialea]

Title: Unable to access filter state from with Golang filter

Description:
Hi team, facing a strange issue attempting to access filter state from within the golang http filter. We have a listener filter which sets keys in both both dynamic metadata and filter state which is successfully accessed by other c++ filters in the chain. When attempting to access these same keys from within the http golang filter, dynamic metadata is empty and the keys do not exist in the filter state.

Any pointers would be appreciated.

[optional Relevant Links:]

envoy/contrib/golang/filters/http/source/go/pkg/http/filter.go

Line 306 in 416cd42

func (f *filterState) GetString(key string) string {

[doujiang24]

Hello @asialea

which is successfully accessed by other c++ filters in the chain

could you please show some related key C++ code? i.e. how they get the values.

And could you please try the Lua http filter to get the dynamicmetadata?

I think there might be some difference to get values which is setted by a listener filter

[asialea]

Sure so here is a code snippet on how these values are set inside our custom listener filter

Network::FilterStatus Filter::onAccept(Network::ListenerFilterCallbacks& cb) {
  StreamInfo::FilterState& filter_state = cb.filterState();
  FilterStateUtils::setFilterState(filter_state, key, value, StateType::ReadOnly, LifeSpan::Connection);
  cb.setDynamicMetadata(filter_name, metadata);
}

Here is the setFilterState method used above

static void setFilterState(StreamInfo::FilterState& filter_state, std::string key, std::string value, StateType state_type, LifeSpan life_span) {
            if (state_type == StateType::Mutable || !filter_state.hasDataWithName(key)) {
                filter_state.setData(key,
                                    std::make_shared<Router::StringAccessorImpl>(value),
                                    state_type,
                                    life_span);
            } else {
                ENVOY_LOG(warn, "FilterStateUtils: Not allowed to call setData() twice on same data name '{}' with ReadOnly state", key);
            }
        }

Here is the code on how the state is retrieved in a custom http filter later on in the chain. These same values from filter state is also able to be accessed by the access logger using FormatStrings

Http::FilterHeadersStatus CustomFilter::decodeHeaders(Http::RequestHeaderMap& headers, bool) {
  const StreamInfo::FilterStateSharedPtr& filter_state = decoder_callbacks_->streamInfo().filterState();
  auto id= FilterStateUtils::getFilterStateStringData(filter_state, key);
}

Here is the getFilterStateStringData method used above

        static std::string getFilterStateStringData(const StreamInfo::FilterState& filter_state, absl::string_view key) {
            auto filter_state_object = filter_state.getDataReadOnly<Router::StringAccessor>(key);
            if (filter_state_object == nullptr) {
                return EMPTY_STRING;
            }

            return std::string(filter_state_object->asString());
        }

[doujiang24]

https://github.com/envoyproxy/envoy/blob/main/contrib%2Fgolang%2Ffilters%2Fhttp%2Fsource%2Fgolang_filter.cc#L1242-L1244
this is how golang plugin get the filter state, I'll take a deeper look tomorrow.

[doujiang24]

okay, I see. we should use Router::StringAccessorImpl & Router::StringAccessor instead of GoStringFilterState, it could be better compatibility.
@StarryVae Are you interested to improve it?