Sodman
commented
3 years ago Hi @thinhtranquoc. While the calls will always technically be async (as we don't want to block Envoy, we're on the critical request path!), there is a way to do what I believe you're probably trying to do, which is essentially:
- Receive a request in Envoy
- Send a request to some external service
- Wait for the response
- If the response fits some criteria, allow continue, otherwise reject request.
You can do this by making an async request, pausing via a StopIteration, and then in the callback if everything looks good you can resume iteration with a call to proxy_continue_stream.
Here is an example of this exact flow working using our AssemblyScript proxy runtime - https://github.com/solo-io/proxy-runtime/blob/master/examples/auth/assembly/index.ts#L37-L60
thinhtranquoc
I see an example for httpcall https://github.com/envoyproxy/envoy-wasm/blob/dfb104874b3babc7e676aaa0199f2926410c0671/test/extensions/filters/http/wasm/test_data/async_call_cpp.cc#L15
I have a question. How to not using async in this case? Because I want to return the result of the external API.
auto callback = [context_id](uint32_t headerCount, size_t body_size, uint32_t trailerCount) { WasmDataPtr wdpGhmv = getHeaderMapValue(WasmHeaderMapType::HttpCallResponseHeaders, ":status"); uint32_t status = std::stoi(wdpGhmv->toString()); WasmDataPtr wdpBody = getBufferBytes(WasmBufferType::HttpCallResponseBody, 0, body_size); std::string reponse = wdpBody->toString(); getContext(context_id)->setEffectiveContext(); if (status == 200){ sendLocalResponse(428, "Precondition Required", reponse, {}); return FilterHeadersStatus::StopIteration; } };