FastAPI graphql subscriptions

Question

I try to implement simple graphql subscription on FastAPI.

According to documentations but it is not working

import asyncio

import graphene
from fastapi import FastAPI
from starlette.graphql import GraphQLApp
from graphql.execution.executors.asyncio import AsyncioExecutor
from starlette.websockets import WebSocket


class Query(graphene.ObjectType):
    hello = graphene.String(name=graphene.String(default_value="stranger"))

    async def resolve_hello(self,info,name):
        return "Hello " + name

class Subscription(graphene.ObjectType):
    count = graphene.Int(upto=graphene.Int())

    async def subscribe_count(root, info, upto=3):
        for i in range(upto):
            yield i
            await asyncio.sleep(1)

app = FastAPI()


schema = graphene.Schema(query=Query, subscription=Subscription)
app.add_route("/", GraphQLApp(schema=schema, executor_class=AsyncioExecutor))

I googled and found that i might need to implement subscription-server like for Sanic or Aiohttp

I try but it doesn't work yet

from graphql_ws.websockets_lib import WsLibSubscriptionServer

subscription_server = WsLibSubscriptionServer(schema)

@app.websocket("/subscriptions")
async def subscriptions(websocket: WebSocket):
    await subscription_server.handle(websocket)
    return websocket

Error recieve:

 return self.ws.open is False
AttributeError: 'WebSocket' object has no attribute 'open'

What i'm doing wrong and how it could be solved? Thank you.

score 1 · Answer 1 · answered Aug 04 '21 at 19:47

I figured it out

below is workable solution

import asyncio

import graphene
import pydantic
from fastapi import FastAPI
from starlette_graphene3 import GraphQLApp, make_playground_handler
from graphene_pydantic import PydanticObjectType


class Subscription(graphene.ObjectType):
    count = graphene.String()

    async def subscribe_count(root, info):
        for i in range(300):
            yield f"{i}"
            await asyncio.sleep(1)

schema = graphene.Schema(query=Query, subscription=Subscription)


app.mount("/", GraphQLApp(schema, on_get=make_playground_handler()))

FastAPI graphql subscriptions

1 Answers1