Server Sent Events

[tomchristie]

It'd be really neat to offer built-in support for server sent events, which are a way for servers to stream events to an HTTP client.

(Similar to WebSockets, but uni-directional)

with httpx.stream("GET", "https://www.example.org/sse") as response:
    for sse in response.iter_sse():
        print(sse.data, sse.event, sse.id, sse.retry)

We'd probably also want to include an sse.json() helper method.

Useful resources...

• https://www.html5rocks.com/en/tutorials/eventsource/basics/
• https://sysid.github.io/sse/
• https://pgjones.gitlab.io/quart/tutorials/broadcast_tutorial.html

Not sure if this has come up before or not, but it'd be a really neat feature for us to offer, for relatively little effort.

[simonw]

I really like this. SSE are a under-used feature of the web in my opinion - I could absolutely see myself hooking up a really simple message bus between two machines using SSE served by Starlette and received by HTTPX.

[florimondmanca]

FWIW, I had played with SSE myself in Bocadillo at the time, so just linking to the user docs and the server-side encoding implementation in case they could be useful here, as some extra reference material.

[havardthom]

+1 on this feature. Using FastAPI with sse-starlette + async integration tests with HTTPX testclient. Having a hard time testing my SSE endpoints due to lack of async testclients for SSE

[t94j0]

+1 This is the recommended option with FastAPI and sse-starlette. Would be really nice to have this feature

[dusty-phillips]

A couple more references:

• https://github.com/aio-libs/aiohttp-sse
• https://github.com/ebraminio/aiosseclient
• https://github.com/sysid/sse-starlette

[harshitsinghai77]

Is this issue open? I would like to contribute if this is open. Thanks.

[florimondmanca]

@harshitsinghai77 Sure, looks like this is open and contributions and drafts are welcome. :)

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[tomchristie]

Still valid thx, @stale bot.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[johtso]

Guessing this is still valid..

[tomchristie]

We should probably bump up the durations on this stale bot. (Wasn't expecting that it'd repeatedly attempt closes after the first attempt) 😐

[abersheeran]

Surprised that this issue has been open for over a year. I just recently added functionality to rpc.py and wrote a code for parsing SSE. If anyone is interested in this, I'll be making a PR to httpx this week. https://github.com/abersheeran/rpc.py/blob/master/rpcpy/client.py#L211-L243

[tomchristie]

Ok. Probably a good plan would be to sketch out the API you'd propose, before submitting a pull request.

[tomchristie]

We should also strongly consider if we really want to have this as functionality in the core package or not. Feasible that we should drop this ticket, but allow for a third party implementation.

For example, this'd make for a perfectly reasonable API, without us having to add additional functionality to httpx itself...

import httpx
from httpx_sse import iter_sse

with httpx.stream("GET", "https://www.example.org/sse") as response:
    for sse in iter_sse(response):
        print(sse.data, sse.event, sse.id, sse.retry)

[florimondmanca]

I worked on an httpx-sse package that I justed pushed here: https://github.com/florimondmanca/httpx-sse

The API is a bit different from what @tomchristie suggested. This is because the spec requires us to prepare or check some things on the request or the response.

I've thought about making connect_sse()/ aconnect_sse() handle reconnections, but that would be a lot more work and may not necessarily fit all use cases, as implementation needs may vary. So I've let that to a "how-to" guide in the project README.

import httpx
from httpx_sse import connect_sse

with httpx.Client() as client:
    with connect_sse(client, "http://localhost:8000/sse") as event_source:
        for sse in event_source.iter_sse():
            print(sse.event, sse.data, sse.id, sse.retry)

This has not been released to PyPI yet. I'd be happy for folks to try that out first. :-)

Edit: released, https://pypi.org/project/httpx-sse/0.1.0

[MrSalman333]

very interested in this