Client can not connect to Proxy

[dirsigler]

Describe the bug

We are currently evaluating the use of the ConfigCat Proxy in our environment to reduce the network traffic and config download stress issued against the ConfigCat platform.

During the evaluation I faced some issues with basic connectivity with a sample Golang application.
As demonstrated in the Proxy documentation I started a local Proxy Container instance containing a demo SDK Key with identifier.
Then to verify the Client connection I wrote simple Golang application, initialising the ConfigCat client with the Proxy as BaseURL and my Key identifier.

During client registration I see following error message:

go run .
INFO[0000] [0] fetching from http://127.0.0.1:8050
ERRO[0000] [1103] config fetch failed: unexpected error occurred while trying to fetch config JSON: Get "http://127.0.0.1:8050/configuration-files/my_demo/config_v5.json": context canceled

To reproduce

Create a ConfigCat config with a FeatureFlag. In my case a TextFlag with "Hello World!" as string.

1. First spin up the proxy locally

docker run -d --name configcat-proxy \
-p 8050:8050 -p 8051:8051 -p 50051:50051 \
-e CONFIGCAT_SDKS='{"my_demo":"YOUR_ORG/SOME_SECRET_KEY"}' \
-e CONFIGCAT_LOG_LEVEL="debug" \
configcat/proxy

2. Start a Golang Client.
   In this example I made it a little HTTP server because it was further used in Docker Compose to verify the stack, but running as go run . should do fine.

package main

import (
	"fmt"
	"log"
	"net/http"

	configcat "github.com/configcat/go-sdk/v8"
)

type application struct {
	client *configcat.Client
}

func (app *application) featureFlagHandler(w http.ResponseWriter, r *http.Request) {
	log.Println("received call")

	allVals := app.client.GetAllValues(nil)

	for k, v := range allVals {
		fmt.Fprintf(w, "Got Key: %s\n Got Value: %v", k, v)
	}

	app.client.Close()
}

func main() {
	mux := http.NewServeMux()

	client := configcat.NewCustomClient(
		configcat.Config{
			BaseURL: "http://127.0.0.1:8050",
			SDKKey:  "my_demo",
			Logger:  configcat.DefaultLogger(configcat.LogLevelDebug),
		},
	)

	app := application{
		client: client,
	}

	mux.HandleFunc("/flag", app.featureFlagHandler)

	err := http.ListenAndServe(":8080", mux)
	if err != nil {
		log.Fatalf("failed to start HTTP server")
	}
}

Expected behavior

The Golang application should connect to the proxy and access the FeatureFlag.

Currently solutions via curl and python work as expected locally:

curl http://127.0.0.1:8050/configuration-files/my_demo/config_v5.json -X GET
{"f":{}}%

curl -I http://127.0.0.1:8050/configuration-files/my_demo/config_v5.json -X GET
HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
Access-Control-Expose-Headers: Content-Length,ETag,Date,Content-Encoding
Cache-Control: max-age=0, must-revalidate
Content-Type: application/json
Etag: W/"7cd89cdf0f515b44"
Date: Tue, 28 Nov 2023 12:05:35 GMT
Content-Length: 132

#!/usr/bin/env python3

import configcatclient

client = configcatclient.get('my_demo',
    configcatclient.ConfigCatOptions(
        polling_mode=configcatclient.PollingMode.auto_poll(),
        base_url='http://127.0.0.1:8050'
    )
)

value = client.get_value(
    'MY_FEATURE_FLAG',
    False,
)

print(value)

python main.py
Hello World!

Screenshots

[z4kn4fein]

Hi @dirsigler, thank you for reporting this issue! I'm going to investigate what's going wrong and let you know here about the results.

[z4kn4fein]

Hi @dirsigler, I've released a new version from the Proxy (v0.2.4). I've identified an issue related to the GZip compression of HTTP responses which is utilized by Go's http client by default. Other platforms you mentioned possibly not requested the response compressed so they got it correctly.

Could you please check the latest Proxy version that it works on your end as expected? Thanks!

[dirsigler]

Impressive work!

At least for my local test stack this solution works without any problems. Therefore I would assume this issue closed.
Thank you very much for your help.