Quarkus REST Client - 411 Length Required when uploading file to Fortinet appliance

I'm using Quarkus to POST a file to an external Fortinet appliance. However, the service enforces strict HTTP protocol constraints and returns:

411 Length Required

The Quarkus REST client interface:

@RegisterRestClient(configKey = "external-api")
@Path("upload")
public interface ExternalApi {
    @POST
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    @Produces(MediaType.APPLICATION_JSON)
    Response submitFile(ClientMultipartForm form);
}


@ApplicationScoped
public class SubmitFileHelper {

    @RestClient
    fortiNetApi fortiNetApi;

    public SubmitFileResponse submitFile(byte[] fileBytes, String originalFilename) {
        ClientMultipartForm form = createMultipartForm(fileBytes, originalFilename);
        return fortiNetApi.submitFile(form);
    }

    private ClientMultipartForm createMultipartForm(byte[] fileBytes, String originalFilename) {
        Buffer buffer = Buffer.buffer(fileBytes);

        return ClientMultipartForm.create()
                .binaryFileUpload("file", originalFilename, buffer, "application/octet-stream");
    }
}

When invoking submitFile(form), I consistently get a 411 Length Required from the Fortinet service. I do see that the Content-Length is being set in the debug logs..

I suspect the issue may be related to chunked transfer encoding, which Fortinet may be blocking due to its strict HTTP protocol constraints. I found something similar for Restlet where the solution was to disable chunking by buffering the request entity. Is there a Quarkus equivalent of this workaround?

Environment:

Quarkus 3.19.4 quarkus-rest-client-reactive Java 21

Any input from Quarkus/REST experts would be highly appreciated.

Solution given by geoand Change the max chunk size property to a value where you are confident it will be larger than the payload.

If the problem is that the server doesn't like chunks, then you need to make sure the REST Client doesn't chunk the input. This can be done by setting:

quarkus.rest-client.max-chunk-size

to a value larger than the expected payload.

Note that this will change the max chunk size for all REST Clients, so you can also used:

quarkus.rest-client."my-client".max-chunk-size to limit the scope of the change to specific clients.