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https://github.com/florimondmanca/httpx-sse
Consume Server-Sent Event (SSE) messages with HTTPX
https://github.com/florimondmanca/httpx-sse
Last synced: 10 days ago
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Consume Server-Sent Event (SSE) messages with HTTPX
- Host: GitHub
- URL: https://github.com/florimondmanca/httpx-sse
- Owner: florimondmanca
- License: mit
- Created: 2022-11-06T12:46:11.000Z (about 2 years ago)
- Default Branch: master
- Last Pushed: 2024-04-18T07:46:17.000Z (7 months ago)
- Last Synced: 2024-10-18T22:13:55.933Z (24 days ago)
- Language: Python
- Size: 40 KB
- Stars: 129
- Watchers: 4
- Forks: 8
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
# httpx-sse
[](https://dev.azure.com/florimondmanca/public/_build?definitionId=19)
[](https://codecov.io/gh/florimondmanca/httpx-sse)
[](https://pypi.org/project/httpx-sse)
Consume [Server-Sent Event (SSE)](https://html.spec.whatwg.org/multipage/server-sent-events.html#server-sent-events) messages with [HTTPX](https://www.python-httpx.org).
**Table of contents**
- [Installation](#installation)
- [Quickstart](#quickstart)
- [How-To](#how-to)
- [API Reference](#api-reference)
## Installation
**NOTE**: This is beta software. Please be sure to pin your dependencies.
```bash
pip install httpx-sse=="0.4.*"
```
## Quickstart
`httpx-sse` provides the [`connect_sse`](#connect_sse) and [`aconnect_sse`](#aconnect_sse) helpers for connecting to an SSE endpoint. The resulting [`EventSource`](#eventsource) object exposes the [`.iter_sse()`](#iter_sse) and [`.aiter_sse()`](#aiter_sse) methods to iterate over the server-sent events.
Example usage:
```python
import httpx
from httpx_sse import connect_sse
with httpx.Client() as client:
with connect_sse(client, "GET", "http://localhost:8000/sse") as event_source:
for sse in event_source.iter_sse():
print(sse.event, sse.data, sse.id, sse.retry)
```
You can try this against this example Starlette server ([credit](https://sysid.github.io/sse/)):
```python
# Requirements: pip install uvicorn starlette sse-starlette
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 {"data": i}
async def sse(request):
generator = numbers(1, 5)
return EventSourceResponse(generator)
routes = [
Route("/sse", endpoint=sse)
]
app = Starlette(routes=routes)
if __name__ == "__main__":
uvicorn.run(app)
```
## How-To
### Calling into Python web apps
You can [call into Python web apps](https://www.python-httpx.org/async/#calling-into-python-web-apps) with HTTPX and `httpx-sse` to test SSE endpoints directly.
Here's an example of calling into a Starlette ASGI app...
```python
import asyncio
import httpx
from httpx_sse import aconnect_sse
from sse_starlette.sse import EventSourceResponse
from starlette.applications import Starlette
from starlette.routing import Route
async def auth_events(request):
async def events():
yield {
"event": "login",
"data": '{"user_id": "4135"}',
}
return EventSourceResponse(events())
app = Starlette(routes=[Route("/sse/auth/", endpoint=auth_events)])
async def main():
async with httpx.AsyncClient(app=app) as client:
async with aconnect_sse(
client, "GET", "http://localhost:8000/sse/auth/"
) as event_source:
events = [sse async for sse in event_source.aiter_sse()]
(sse,) = events
assert sse.event == "login"
assert sse.json() == {"user_id": "4135"}
asyncio.run(main())
```
### Handling reconnections
_(Advanced)_
`SSETransport` and `AsyncSSETransport` don't have reconnection built-in. This is because how to perform retries is generally dependent on your use case. As a result, if the connection breaks while attempting to read from the server, you will get an `httpx.ReadError` from `iter_sse()` (or `aiter_sse()`).
However, `httpx-sse` does allow implementing reconnection by using the `Last-Event-ID` and reconnection time (in milliseconds), exposed as `sse.id` and `sse.retry` respectively.
Here's how you might achieve this using [`stamina`](https://github.com/hynek/stamina)...
```python
import time
from typing import Iterator
import httpx
from httpx_sse import connect_sse, ServerSentEvent
from stamina import retry
def iter_sse_retrying(client, method, url):
last_event_id = ""
reconnection_delay = 0.0
# `stamina` will apply jitter and exponential backoff on top of
# the `retry` reconnection delay sent by the server.
@retry(on=httpx.ReadError)
def _iter_sse():
nonlocal last_event_id, reconnection_delay
time.sleep(reconnection_delay)
headers = {"Accept": "text/event-stream"}
if last_event_id:
headers["Last-Event-ID"] = last_event_id
with connect_sse(client, method, url, headers=headers) as event_source:
for sse in event_source.iter_sse():
last_event_id = sse.id
if sse.retry is not None:
reconnection_delay = sse.retry / 1000
yield sse
return _iter_sse()
```
Usage:
```python
with httpx.Client() as client:
for sse in iter_sse_retrying(client, "GET", "http://localhost:8000/sse"):
print(sse.event, sse.data)
```
## API Reference
### `connect_sse`
```python
def connect_sse(
client: httpx.Client,
method: str,
url: Union[str, httpx.URL],
**kwargs,
) -> ContextManager[EventSource]
```
Connect to an SSE endpoint and return an [`EventSource`](#eventsource) context manager.
This sets `Cache-Control: no-store` on the request, as per the SSE spec, as well as `Accept: text/event-stream`.
If the response `Content-Type` is not `text/event-stream`, this will raise an [`SSEError`](#sseerror).
### `aconnect_sse`
```python
async def aconnect_sse(
client: httpx.AsyncClient,
method: str,
url: Union[str, httpx.URL],
**kwargs,
) -> AsyncContextManager[EventSource]
```
An async equivalent to [`connect_sse`](#connect_sse).
### `EventSource`
```python
def __init__(response: httpx.Response)
```
Helper for working with an SSE response.
#### `response`
The underlying [`httpx.Response`](https://www.python-httpx.org/api/#response).
You may use this to perform more operations and checks on the response, such as checking for HTTP status errors:
```python
with connect_sse(...) as event_source:
event_source.response.raise_for_status()
for sse in event_source.iter_sse():
...
```
#### `iter_sse`
```python
def iter_sse() -> Iterator[ServerSentEvent]
```
Decode the response content and yield corresponding [`ServerSentEvent`](#serversentevent).
Example usage:
```python
for sse in event_source.iter_sse():
...
```
#### `aiter_sse`
```python
async def iter_sse() -> AsyncIterator[ServerSentEvent]
```
An async equivalent to `iter_sse`.
### `ServerSentEvent`
Represents a server-sent event.
* `event: str` - Defaults to `"message"`.
* `data: str` - Defaults to `""`.
* `id: str` - Defaults to `""`.
* `retry: str | None` - Defaults to `None`.
Methods:
* `json() -> Any` - Returns `sse.data` decoded as JSON.
### `SSEError`
An error that occurred while making a request to an SSE endpoint.
Parents:
* `httpx.TransportError`
## License
MIT