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Metadata-Version: 2.1 Name: sse-starlette Version: 2.2.1 Summary: SSE plugin for Starlette Author-email: sysid <sysid@gmx.de> License: BSD-3-Clause Project-URL: Source, https://github.com/sysid/sse-starlette 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 Classifier: Programming Language :: Python :: 3.10 Classifier: Programming Language :: Python :: 3.11 Classifier: Programming Language :: Python :: 3.12 Classifier: Topic :: Internet :: WWW/HTTP Requires-Python: >=3.9 Description-Content-Type: text/markdown License-File: LICENSE License-File: AUTHORS Requires-Dist: anyio>=4.7.0 Requires-Dist: starlette>=0.41.3 Provides-Extra: examples Requires-Dist: fastapi; extra == "examples" Provides-Extra: uvicorn Requires-Dist: uvicorn>=0.34.0; extra == "uvicorn" # Server Sent Events for [Starlette](https://github.com/encode/starlette) and [FastAPI](https://fastapi.tiangolo.com/) [](https://pepy.tech/project/sse-starlette) [![PyPI Version][pypi-image]][pypi-url] [![Build Status][build-image]][build-url] [![Code Coverage][coverage-image]][coverage-url] > Implements the [Server-Sent Events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events) specification. 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:  **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()) ``` # Thread Safety with SQLAlchemy Sessions and Similar Objects The streaming portion of this package is accomplished via anyio TaskGroups. Care needs to be taken to avoid passing objects that are not thread-safe to generators you use to yield streaming data. For example, if you are using SQLAlchemy, you should not use/pass an `AsyncSession` object to your generator: ```python # ❌ This can result in "The garbage collector is trying to clean up non-checked-in connection..." errors async def bad_route(): async with AsyncSession() as session: async def generator(): async for row in session.execute(select(User)): yield dict(data=row) return EventSourceResponse(generator) ``` Instead, ensure you create sessions within the generator itself ```python # ✅ This is safe async def good_route(): async def generator(): async with AsyncSession() as session: async for row in session.execute(select(User)): yield dict(data=row) return EventSourceResponse(generator) ``` ## 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"}), ) ``` ### SSE Send Timeout To avoid 'hanging' connections in case HTTP connection from a certain client was kept open, but the client stopped reading from the connection you can specifiy a send timeout (see [#89](https://github.com/sysid/sse-starlette/issues/89)). ```python EventSourceResponse(..., send_timeout=5) # terminate hanging send call after 5s ``` ### 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`). ### Using pytest to test SSE Endpoints When testing more than a single SSE endpoint via pytest, one may encounter the following error: `RuntimeError: <asyncio.locks.Event object at 0xxxx [unset]> is bound to a different event loop`. A workaround to fix this error is to use the following fixture on all tests that use SSE: ```python @pytest.fixture def reset_sse_starlette_appstatus_event(): """ Fixture that resets the appstatus event in the sse_starlette app. Should be used on any test that uses sse_starlette to stream events. """ # See https://github.com/sysid/sse-starlette/issues/59 from sse_starlette.sse import AppStatus AppStatus.should_exit_event = None ``` For details, see [Issue#59](https://github.com/sysid/sse-starlette/issues/59#issuecomment-1961678665). ## Development, Contributing 1. install pdm: `pip install pdm` 2. install dependencies using pipenv: `pdm install -d`. 3. To run tests: ### Makefile - make sure your virtualenv is active - check `Makefile` for available commands and development support, e.g. run the unit tests: ```shell make test make tox ``` 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