feat: sse ping_interval events

[RenameMe1]

Description

I would like to propose a solution for issue #4082.

• Created new classes ASGIStreamingSSEResponse which supported sending ping messages

Closes

#4082

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 4 lines in your changes missing coverage. Please review.

Project coverage is 98.36%. Comparing base (a98d958) to head (165dd59).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
litestar/response/sse.py	92.30%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4098      +/-   ##
==========================================
- Coverage   98.37%   98.36%   -0.01%     
==========================================
  Files         348      348              
  Lines       15890    15944      +54     
  Branches     1755     1762       +7     
==========================================
+ Hits        15631    15683      +52     
- Misses        122      123       +1     
- Partials      137      138       +1     

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[RenameMe1]

@sobolevn can you help me please with litestar/response/streaming.py:154: error: in mypy.

I don't follow why this an error occur.

• AsyncIteratorWrapper has __anext__
  

  litestar/litestar/utils/sync.py

  Line 48 in 027ce12

  class AsyncIteratorWrapper(Generic[T]):

• all content wraps by _ServerSentEventIterator(AsyncIteratorWrapper[bytes]) in ServerSentEvent
  https://github.com/litestar-org/litestar/blob/027ce12a64711f90c9d13b79d753be81779e6db0/litestar/response/sse.py#L130C7-L130C22

• ...
  

  litestar/litestar/response/streaming.py

  Line 90 in 027ce12

  self.iterator: AsyncIterable[str | bytes] | AsyncGenerator[str | bytes, None] = (

[provinzkraut]

This should not be named timeout as it is not a timeout.

[provinzkraut]

I would suggest a different design. Take a look at how the stream handles client disconnects. Ideally, the two background tasks can share the same task group. Otherwise, there's unnecessary overhead involved, and cancellations become quite complex

[euri10]

I added some minor comments.
We'd need tests for the missing coverage and to test the functionnality too but this looks good overall!

[RenameMe1]

I added some minor comments. We'd need tests for the missing coverage and to test the functionnality too but this looks good overall!

I have read all the SSE tests and don't understand how I can test it. Can you help me, please?

I thought I would create an example with ping_interval and test it.

• https://github.com/litestar-org/litestar/blob/main/docs/examples/responses/sse_responses.py

• https://github.com/litestar-org/litestar/blob/main/tests/examples/test_responses/test_sse_responses.py

[RenameMe1]

@provinzkraut, friendly ping. Can you review, please?

I'm moved out work on ping messages to another class ASGIStreamingSSERespnse. Additionaly added state to event generator

[euri10]

I didnt check in details thechanges but one thing I'd like to see if you dont mind is a little addition in the docs for that feature: https://docs.litestar.dev/latest/usage/responses.html#server-sent-event-responses

something like that below this would do the job:

In your iterator function you can yield integers, strings or bytes, the message sent in that case will have message as the event_type if the ServerSentEvent has no event_type set, otherwise it will use the event_type specified, and the data will be the yielded value.

If ping_interval is set to a positive value, blablabla. It is useful for instance on Telegram blablabla, (see the issue)

[provinzkraut]

Hi @RenameMe1, unfortunately this still doesn't look just right.

The main issue is the separation of concerns here.
We do have a ASGIStreamingResponse. It should not care about SSE specifics. To implement SSE specific functionality, you'll have to implement it on a separate response class (which you did with ASGIStreamingSSEResponse), and then use that when returning an SSE stream.

[github-actions]

Documentation preview will be available shortly at https://litestar-org.github.io/litestar-docs-preview/4098

[RenameMe1]

Hello @provinzkraut, I'm moved out SSE implementation into litestar/response/see.py. Can you see, please?

Thanks for you help, and so sorry for mistakes ><

[RenameMe1]

@provinzkraut, friendly ping. Can you review, please?

I hope, my work is right

[RenameMe1]

@provinzkraut, friendly ping. Can you review, please?

Maybe it would be better to close this PR and let other people do it?