Server Sent Events transport

[tonyrewin]

I want to implement the subject for graphql subscriptions. What is the best way to do that? I tried to rewrite GraphQLTransportWS class and then pass this object to websocket_handler parameter of ariadne's GraphQL(..) init. Am I going well? What would you recommend?

[rafalp]

Hey. Websocket handler is called for websocket protocol. So its different thing than Server Sent Event. I don't have knowledge of SSE to say more about this, but quick google shows that The Guild provides dedicated handler for SSE connections, so perhaps we should provide sse_handler on the GraphQL app to use in this case?

[tonyrewin]

That would be awesome and I've tried to write it by myself, but found WSHandler and HTTPHandler only is there. Not sure if they are useful as base for SSEHandler code

[rafalp]

HTTP handler is closer to what you are trying to accomplish because its HTTP bases. From my understanding SSE handler should use Ariadne's subscribe instead of graphql to run query, and return a HTTP2 response on every event that resolves to not null?

[tonyrewin]

Yes, sure, SSE is HTTP itself, but it is not so obvious how to use it for GraphQL subscription in ariadne. If it is not necessary to implement the separate sse_handler= parameter in API can you please provide an example at least.

[tonyrewin]

Is there any method to reuse HTTPHandler code for graphql subscriptions or recommendations how to deal with EventSource better way?

[cancan101]

FYI, SSE does not require HTTP/2.

I think the rough approach here would be to pull code like this:

ariadne/ariadne/asgi/handlers/graphql_ws.py

Lines 201 to 217 in 9b55730

	operation_type = get_operation_type(query_document, data.get("operationName"))
	if operation_type == OperationType.SUBSCRIPTION:
	await self.start_websocket_operation(
	websocket,
	data,
	context_value,
	query_document,
	operation_id,
	operations,
	)
	else:
	if self.http_handler is None:
	raise TypeError(
	"http_handler is not set, call configure method to initialize it"
	)
	_, result = await self.http_handler.execute_graphql_query(websocket, data)

into here on the http handler:

ariadne/ariadne/asgi/handlers/http.py

Lines 146 to 167 in 9b55730

	async def graphql_http_server(self, request: Request) -> Response:
	"""Handles the HTTP request with GraphQL query.
	Extracts GraphQL query data from requests and then executes it using
	the `execute_graphql_query` method.
	Returns the JSON response from Sta
	If request's data was invalid or missing, plaintext response with
	error message and 400 status code is returned instead.
	# Required arguments:
	`request`: the `Request` instance from Starlette or FastAPI.
	"""
	try:
	data = await self.extract_data_from_request(request)
	except HttpError as error:
	return PlainTextResponse(error.message or error.status, status_code=400)
	success, result = await self.execute_graphql_query(request, data)
	return await self.create_json_response(request, result, success)

[cancan101]

Here is the RFC for this protocol: https://github.com/graphql/graphql-over-http/blob/main/rfcs/GraphQLOverSSE.md