potentially (huge) Async File download

[Froidoh]

Hello everyone!

Edit: So, the root cause for the following problem is:

io.quarkus quarkus-smallrye-opentracing

When I disable this dependency, everything works like a charm.

The problem is, I need to use opentracing sighs, so I currently face a situation of mutual exclusive feature-requests

Original post below

First of, let me say: Thanks for all the effort going into this project!

I am using Quarkus 2.10.3.Final

Overall goal:

Allow downloading potentially huge files as a stream, to mitigate need to allocate a lot of memory

Solution that worked:

@Path("/files")
@NonBlocking // All methods should be non-blocking!
public class FileController {

    @GET
    @Path("{fileId}")
    @Produces(MediaType.APPLICATION_OCTET_STREAM)
    public Multi<Buffer> downloadFile(@PathParam("fileId") BigInteger id) {
        try {
            return downloadService.download(id);
        } catch (Exception e) {
            LOG.error("Failed to download file. Exception: ", e);
            throw new FileInformationNotFoundException(id);
        }
    }
}

/* 
 * Relevant imports
 * import io.smallrye.mutiny.Uni;
 * import io.vertx.core.file.OpenOptions;
 * import io.vertx.mutiny.core.Vertx;
*/

@Singleton
@NonBlocking
public class FileDownloadService {

    @Inject
    FileRepository repo;

    private final Vertx vertx;

    @Inject
    public FileDownloadService(Vertx vertx) {
        this.vertx = vertx;
    }

	public Multi<Buffer> download(BigInteger fileId) {
	    return repo.findById(fileId)
	            .onItem()
	            .ifNull()
	            .failWith(new FileInformationNotFoundException(fileId))
	            .flatMap(info -> {
	                return vertx.fileSystem().open(info.path, new OpenOptions()
	                    .setRead(true)
	                    .setWrite(false)
	                    .setCreate(false));
	            }).onItem()
	            .transformToMulti(AsyncFile::toMulti);
	}
}

New requirement:

Add custom header to response and also set "Content-Type"-Header.

I found https://stackoverflow.com/a/72524030

So I tried it like this:

// Inside FileController

@GET
@Path("download/{fileId}")
@Produces(MediaType.APPLICATION_OCTET_STREAM)
public Uni<Response> downloadFile(@PathParam("fileId") BigInteger id) {
    try {
        return downloadService.download(id);
    } catch (Exception e) {
        LOG.error("Failed to download file. Exception: ", e);
        throw new FileInformationNotFoundException(id);
    }
}

// Inside public class FileDownloadService

public Uni<Response> download(BigInteger archiveId) {
	// Simplified version
    String testPath = "path/to/file";
    final OpenOptions openOptions = new OpenOptions().setCreate(false).setWrite(false).setCreate(false);
    return vertx.fileSystem().open(testPath, openOptions)
            .onItem()
            .transform(asyncFile -> Response.ok(asyncFile, "image/png")
                    .header("X-Content-Type", "image/png") // Just another test for a 
                    .header("Content-Disposition", "attachment;filename=\"JustATest.txt\"")
                    .build());

   // This should be the actual code
   /* return repo.findById(archiveId)
            .onItem()
            .ifNull()
            .failWith(new FileInformationNotFoundException(archiveId))
            .flatMap(info -> {
                final OpenOptions openOptions = new OpenOptions().setCreate(false).setWrite(false).setCreate(false);
                return vertx.fileSystem().open(info.path, openOptions);
            })
            .onItem()
            .transform(asyncFile -> Response.ok(asyncFile, "image/png")
                    .header("X-Content-Type", "image/png") // Here the actual media type stored in the db should go
                    .header("Content-Disposition", "attachment;filename=\"JustATest.txt\"")
                    .build()
            );*/
}

Sadly I always get a response of:

Returning an AsyncFile is not supported with WriterInterceptors","stack":"java.lang.UnsupportedOperationException: Returning an AsyncFile is not supported with WriterInterceptors

I found the error message in the quarkus source code, but I am not sure what I am doing wrong or how I can mitigate it.

Also I can't seem to overwrite the content-type header at all... it's always: "content-type: application/json; charset=utf-8"... this can be mitigated on the client side, but with a lot of effort :/