Metadata-Version: 2.1
Name: sse-starlette
Version: 1.6.1
Summary: "SSE plugin for Starlette"
Home-page: https://github.com/sysid/sse-starlette
Author: sysid
Author-email: sysid@gmx.de
Classifier: Development Status :: 5 - Production/Stable
Classifier: Environment :: Web Environment
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: BSD License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.9
Requires-Python: >=3.8
Description-Content-Type: text/markdown
License-File: LICENSE
License-File: AUTHORS
Requires-Dist: starlette

# Server Sent Events for [Starlette](https://github.com/encode/starlette) and [FastAPI](https://fastapi.tiangolo.com/)

[![PyPI Version][pypi-image]][pypi-url]
[![Build Status][build-image]][build-url]
[![Code Coverage][coverage-image]][coverage-url]

Background: https://sysid.github.io/server-sent-events/

Installation:

```shell
pip install sse-starlette
```

Usage:

```python
import asyncio
import uvicorn
from starlette.applications import Starlette
from starlette.routing import Route
from sse_starlette.sse import EventSourceResponse

async def numbers(minimum, maximum):
    for i in range(minimum, maximum + 1):
        await asyncio.sleep(0.9)
        yield dict(data=i)

async def sse(request):
    generator = numbers(1, 5)
    return EventSourceResponse(generator)

routes = [
    Route("/", endpoint=sse)
]

app = Starlette(debug=True, routes=routes)

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000, log_level='info')
```

Output:
![output](output.png)

**Caveat:** SSE streaming does not work in combination with [GZipMiddleware](https://github.com/encode/starlette/issues/20#issuecomment-704106436).

Be aware that for proper server shutdown your application must stop all
running tasks (generators). Otherwise you might experience the following warnings
at shutdown: `Waiting for background tasks to complete. (CTRL+C to force quit)`.

Client disconnects need to be handled in your Request handler (see example.py):
```python
async def endless(req: Request):
    async def event_publisher():
        i = 0
        try:
          while True:
              i += 1
              yield dict(data=i)
              await asyncio.sleep(0.2)
        except asyncio.CancelledError as e:
          _log.info(f"Disconnected from client (via refresh/close) {req.client}")
          # Do any other cleanup, if any
          raise e
    return EventSourceResponse(event_publisher())
```

## Special use cases
### Customize Ping
By default, the server sends a ping every 15 seconds. You can customize this by:
1. setting the `ping` parameter
2. by changing the `ping` event to a comment event so that it is not visible to the client
```python
@router.get("")
async def handle():
    generator = numbers(1, 100)
    return EventSourceResponse(
        generator,
        headers={"Server": "nini"},
        ping=5,
        ping_message_factory=lambda: ServerSentEvent(**{"comment": "You can't see\r\nthis ping"}),
    )
```

### Fan out Proxies
Fan out proxies usually rely on response being cacheable. To support that, you can set the value of `Cache-Control`.
For example:
```python
return EventSourceResponse(
        generator(), headers={"Cache-Control": "public, max-age=29"}
    )
```
### Error Handling
See example: `examples/error_handling.py`


### Sending Responses without Async Generators
Async generators can expose tricky error and cleanup behavior especially when they are interrupted.

[Background: Cleanup in async generators](https://vorpus.org/blog/some-thoughts-on-asynchronous-api-design-in-a-post-asyncawait-world/#cleanup-in-generators-and-async-generators).

Example [`no_async_generators.py`](https://github.com/sysid/sse-starlette/pull/56#issue-1704495339) shows an alternative implementation
that does not rely on async generators but instead uses memory channels (`examples/no_async_generators.py`).


## Development, Contributing
1. install pipenv: `pip install pipenv`
2. install dependencies using pipenv: `pipenv install --dev -e .`
3. To run tests, either:
   - `pipenv run pytest`
 
### Makefile
- make sure your virtualenv is active: `pipenv shell`
- check `Makefile` for available commands and development support, e.g. run the unit tests:
```python
make test
```

For integration testing you can use the provided examples in `tests` and `examples`.

If you are using Postman, please see: https://github.com/sysid/sse-starlette/issues/47#issuecomment-1445953826


<!-- Badges -->

[pypi-image]: https://badge.fury.io/py/sse-starlette.svg
[pypi-url]: https://pypi.org/project/sse-starlette/
[build-image]: https://github.com/sysid/sse-starlette/actions/workflows/build.yml/badge.svg
[build-url]: https://github.com/sysid/sse-starlette/actions/workflows/build.yml
[coverage-image]: https://codecov.io/gh/sysid/sse-starlette/branch/master/graph/badge.svg
[coverage-url]: https://codecov.io/gh/sysid/sse-starlette

Copyright © 2020, [sysid](https://sysid.github.io/).
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
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* Neither the name of the copyright holder nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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