How to use the response from DispatchHttpCall as the final result

[TC-wang]

Describe the bug / error

I am trying to use DispatchHttpCall to call a remote service and get the response, then return the response as the final result. But it didn't work.

1. Looks like the types.ActionPause in OnHttpRequestBody didn't work.

The original request was still being sent to upstream, the response received by the client was also the result returned by upstream.

The code is as follows：

func (ctx *testContext) OnHttpRequestHeaders(numHeaders int, endOfStream bool) types.Action {
	proxywasm.LogInfof("OnHttpRequestHeaders...")
	return types.ActionContinue
}

func (ctx *testContext) OnHttpRequestBody(bodySize int, endOfStream bool) types.Action {
	var requestBodySize int
	requestBodySize += bodySize
	if !endOfStream {
		return types.ActionPause
	}
	body, err := proxywasm.GetHttpRequestBody(0, requestBodySize)
	if err != nil {
		proxywasm.LogErrorf("get request body failed: %v", err)
		return types.ActionContinue
	}
	proxywasm.LogErrorf("get request body success: %v", string(body))

	headers := [][2]string{
		{":method", "GET"}, {":authority", "some_authority"}, {"accept", "*/*"}, {":path", "/GET/hello"},
	}
	if _, err := proxywasm.DispatchHttpCall("cluster1", headers, nil, nil,
		5000, httpCallResponseCallback); err != nil {
		proxywasm.LogCriticalf("dispatch httpcall failed: %v", err)
		return types.ActionContinue
	}

	return types.ActionPause
}

func (ctx *testContext) OnHttpResponseHeaders(bodySize int, endOfStream bool) types.Action {
	proxywasm.LogInfof("onHttpResponseHeaders...")
	return types.ActionContinue
}

func (ctx *testContext) OnHttpResponseBody(bodySize int, endOfStream bool) types.Action {
	var responseBodySize int
	responseBodySize += bodySize
	if !endOfStream {
		return types.ActionPause
	}
	body, err := proxywasm.GetHttpResponseBody(0, responseBodySize)
	if err != nil {
		proxywasm.LogErrorf("get response body failed: %v", err)
		return types.ActionContinue
	}

	proxywasm.LogInfof("onHttpResponseBody...: %s", string(body))
	return types.ActionContinue
}

func httpCallResponseCallback(numHeaders, bodySize, numTrailers int) {
	if err := proxywasm.SendHttpResponse(200, [][2]string{
		{"powered-by", "proxy-wasm-go-sdk!!"},
	}, []byte("success"), -1); err != nil {
		proxywasm.LogErrorf("failed to send local response: %v", err)
		proxywasm.ResumeHttpRequest()
	}
	return
}

What is your Envoy/Istio version?

1.22

What is the SDK version?

proxy-wasm-go-sdk@v0.19.1-0.20220822060051-f9d179a57f8c

What is your TinyGo version?

tinygo version 0.25.0 linux/amd64 (using go version go1.19.9 and LLVM version 14.0.0)

[mathetake]

This has been asked really really frequently, and it's impossible to do due to the limitation of Proxy-Wasm. See #364 (comment)