streams as a replacement for progress events... what about upload progress?

[caitp]

It's clear that you could consume a streaming response body at chunk intervals, as a replacement for progress events.

But this doesn't exactly help if you wanted to track the progress of an upload. Just wondering if anyone has had any ideas about that.

[domenic]

The plan is to have uploads be represented by a writable stream that you write to. Then you know the progress: it's the number of bytes you've written divided by the total number of bytes you plan to write.

[yutakahirano]

Imagine a user has a Blob blob. If the user wants to make a fetch with uploading blob, is it desirable to create a ReadableStream from blob just for receiving progress events?

Chrome is able to send a Blob efficiently but creating a ReadableStream from the Blob and sending the ReadableStream manually will disable the optimization. Hence I would like to have a means to receive progress events while sending a Blob directly.

[jakearchibald]

F2F:

• We could make it easy to turn blobs into "bounded streams", that know their total size, and provide a progress callback - but this doesn't work for .json.
• An argument to bodyinit, fetch(url, {progressCallback})
• blob.toStream(), formData.toStream() etc etc
• Observables maybe, but that needs to go through tc39

[wanderview]

Not sure if this is settled or not, but wanted to throw my perspective in.

As an implementer I'd really like progress to be a separate API from the body stream. In order to implement streaming without a perf penalty we need to do some amount of internal buffering. In contrast, progress events currently attempt to provide status based on bytes that are read/write at the OS-level syscalls. Obviously this does not play well with any internal buffering.

So in my mind we must pick one of these:

1. Separate progress API from streams
2. Stream-based progress understanding its measuring progress of internal buffering
3. Stream-based progress measuring OS-level syscalls, but with slow performance

[rajendrarathore]

Yes much needed feature for trace the upload progress.

I hope to see that feature in future release.

[MartinMuzatko]

Has there been any updates in a year? Working examples?

[yutakahirano]

I haven't worked on this issue. Is whatwg/fetch#65 related?

[annevk]

I think we're still waiting for experimentation on top of streams before figuring out exactly what to expose.