FileUploadHandler cannot process concurrent upload request

[eblosug]

How to reproduce this issue:

Run a small test server

import io.netty.handler.codec.http.HttpMethod;
import org.restexpress.Request;
import org.restexpress.Response;
import org.restexpress.RestExpress;
import java.nio.file.Files;

public class TestUploadServer {
    public static void main(String[] args) throws Throwable {
        RestExpress server = new RestExpress().setSupportFileUpload(true);
        server.uri("/upload", new MyController()).action("upload", HttpMethod.POST);
        server.bind(8901);
        server.awaitShutdown();
    }

    static class MyController {
        public String upload(Request request, Response response) throws Exception{
            byte[] data = Files.readAllBytes(request.getUploadedFileAttachment().toPath());
            return "YOU SENT:\n" + new String(data);
        }
    }
}

Create two files to upload:

python3 -c 'print("a"*8000)' > a.txt
python3 -c 'print("b"*8000)' > b.txt

Start the first upload:

curl -v -F upload=@a.txt --limit-rate 1k http://127.0.0.1:8901/upload

After 3 seconds, start the second upload in another terminal:

curl -v -F upload=@b.txt --limit-rate 1k http://127.0.0.1:8901/upload

The first request will not get a response because the controller throws a NoSuchFileException.

The second request will get a response that has a mix of a and bs in the body.

[eblosug]

The issue is that the FileUploadHandler is annotated with @Sharable but it has only one HttpPostRequestDecoder which has internal state.