Streaming multipart hangs for binary files above a certain threshold unless rechunking the body stream

[jgranstrom]

Describe the bug
Note: using 3.0.0-RC1+9-429c3938-SNAPSHOT which includes #2116

Sending a multipart binary file that is above a certain size, close to the StreamingForm buffer of 8192, I assume minus some header size, will cause the stream to hang indefinitely.

To Reproduce
Test server:

Server.serve(
    Http.collectZIO {
      case req @ Method.POST -> !! => (for {
        form <- req.body.asMultipartFormStream
        _ <- form.collectAll
      } yield Response.text("done")
        ).catchAll(e => ZIO.succeed(Response.text(e.toString)))
    }
  )

Sending an image with size 8155 is fine:
http --multipart localhost:8000 "file@./8155.png"
Sending an image with size 8156, or any size above that hangs indefinitely:
http --multipart localhost:8000 "file@./8156.png"

Creating the form manually with a custom buffer size, such as:
form <- StreamingForm(req.body.asStream, boundary, 8193)
Will now happily process one more byte, so 8156 will work, but anything above that will hang

Creating the form manually by first rechunking the body stream, such as:
form <- StreamingForm(req.body.asStream.rechunk(1024), boundary)
Seems to handle arbitrary sizes without hanging, although difficult to test exhaustively.

Expected behaviour
Any file size to be handled by streaming form without hanging. If rechunking the body stream is required for the form processing to work properly, it should probably be done by asMultipartFormStream

[jdegoes]

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[jgranstrom]

Since it doesn't reliably reproduce without a server, I used this test suite in ServerSpec which reproduces it consistently:

      suite("streaming form") {
        val boundary = Boundary("X-INSOMNIA-BOUNDARY")
        val app = Http.collectZIO[Request] { case req =>
          req.body.asMultipartFormStream
            .flatMap(f => f.collectAll)
            .map(form => Response.text(form.map("file").asInstanceOf[FormField.Binary].data.size.toString))
        }

        test("this succeeds"){
          val bytes = Chunk.fill[Byte](8000)(0)
          val form = Form(Chunk(FormField.Binary("file", bytes, MediaType.image.png)))
          val res = app.deploy.body.mapZIO(_.asString).run(
            headers = Headers(Header.ContentType(MediaType.multipart.`form-data`, Some(boundary))),
            body = Body.fromMultipartForm(form, boundary)
          )
          assertZIO(res)(equalTo("8000"))
        } +
          test("this times out") {
          val bytes = Chunk.fill[Byte](8200)(0)
          val form = Form(Chunk(FormField.Binary("file", bytes, MediaType.image.png)))
          val res = app.deploy.body.mapZIO(_.asString).run(
            headers = Headers(Header.ContentType(MediaType.multipart.`form-data`, Some(boundary))),
            body = Body.fromMultipartForm(form, boundary)
          )
          assertZIO(res)(equalTo("8200"))
        }
      },

[andrzejressel]

Weird, it does repro for me in MultipartFormDataStreaming when I remove Server.Config.default.enableRequestStreaming.

EDIT: This is so weird, I'm starting to think Queues are to blame for this ...

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