ASGI

Strawberry comes with a basic ASGI integration. It provides an app that you can use to serve your GraphQL schema. Before using Strawberry’s ASGI support make sure you install all the required dependencies by running:

Terminal window
pip install 'strawberry-graphql[asgi]'

Once that’s done you can use Strawberry with ASGI like so:

server.py
from strawberry.asgi import GraphQL


from api.schema import schema


app = GraphQL(schema)

Every ASGI server will accept this app instance to start the server. For example if you’re using uvicorn you run the app with uvicorn server:app

Options

The GraphQL app accepts the following options at the moment:

Extending the view

The base GraphQL class can be extended by overriding any of the following methods:

get_context

get_context allows to provide a custom context object that can be used in your resolver. You can return anything here, by default we return a dictionary with the request and the response. 

import strawberry
from typing import Union
from strawberry.asgi import GraphQL
from starlette.requests import Request
from starlette.responses import Response




class MyGraphQL(GraphQL):
    async def get_context(
        self, request: Union[Request, WebSocket], response: Optional[Response] = None
    ):
        return {"example": 1}




@strawberry.type
class Query:
    @strawberry.field
    def example(self, info: strawberry.Info) -> str:
        return str(info.context["example"])

Here we are returning a custom context dictionary that contains only one item called “example”.

Then we use the context in a resolver, the resolver will return “1” in this case.

Setting response headers

It is possible to use get_context to set response headers. A common use case might be cookie-based user authentication, where your login mutation resolver needs to set a cookie on the response.

This is possible by updating the response object contained inside the context of the Info object. 

import strawberry




@strawberry.type
class Mutation:
    @strawberry.mutation
    def login(self, info: strawberry.Info) -> bool:
        token = do_login()
        info.context["response"].set_cookie(key="token", value=token)
        return True

Setting background tasks

Similarly, background tasks can be set on the response via the context: 

import strawberry
from starlette.background import BackgroundTask




async def notify_new_flavour(name: str): ...




@strawberry.type
class Mutation:
    @strawberry.mutation
    def create_flavour(self, name: str, info: strawberry.Info) -> bool:
        info.context["response"].background = BackgroundTask(notify_new_flavour, name)

get_root_value

get_root_value allows to provide a custom root value for your schema, this is probably not used a lot but it might be useful in certain situations.

Here’s an example: 

import strawberry
from typing import Union
from strawberry.asgi import GraphQL
from starlette.requests import Request
from starlette.websockets import WebSocket




class MyGraphQL(GraphQL):
    async def get_root_value(self, request: Union[Request, WebSocket]):
        return Query(name="Patrick")




@strawberry.type
class Query:
    name: str

Here we are returning a Query where the name is “Patrick”, so we when requesting the field name we’ll return “Patrick” in this case.

process_result

process_result allows to customize and/or process results before they are sent to the clients. This can be useful logging errors or hiding them (for example to hide internal exceptions).

It needs to return an object of GraphQLHTTPResponse and accepts the request and the execution results. 

from strawberry.asgi import GraphQL
from strawberry.http import GraphQLHTTPResponse
from strawberry.types import ExecutionResult
from starlette.requests import Request




class MyGraphQL(GraphQL):
    async def process_result(
        self, request: Request, result: ExecutionResult
    ) -> GraphQLHTTPResponse:
        data: GraphQLHTTPResponse = {"data": result.data}


        if result.errors:
            data["errors"] = [err.formatted for err in result.errors]


        return data

In this case we are doing the default processing of the result, but it can be tweaked based on your needs.

decode_json

decode_json allows to customize the decoding of HTTP JSON requests. By default we use json.loads but you can override this method to use a different decoder. 

from strawberry.asgi import GraphQL
from typing import Union
import orjson




class MyGraphQLView(GraphQL):
    def decode_json(self, data: Union[str, bytes]) -> object:
        return orjson.loads(data)

Make sure your code raises json.JSONDecodeError or a subclass of it if the JSON cannot be decoded. The library shown in the example above, orjson , does this by default.

encode_json

encode_json allows to customize the encoding of HTTP and WebSocket JSON responses. By default we use json.dumps but you can override this method to use a different encoder. 

import json
from strawberry.asgi import GraphQL




class MyGraphQLView(GraphQL):
    def encode_json(self, data: object) -> str:
        return json.dumps(data, indent=2)

render_graphql_ide

In case you need more control over the rendering of the GraphQL IDE than the graphql_ide option provides, you can override the render_graphql_ide method. 

from strawberry.asgi import GraphQL
from starlette.responses import HTMLResponse, Response




class MyGraphQL(GraphQL):
    async def render_graphql_ide(self, request: Request) -> Response:
        custom_html = """<html><body><h1>Custom GraphQL IDE</h1></body></html>"""


        return HTMLResponse(custom_html)

on_ws_connect

By overriding on_ws_connect you can customize the behavior when a graphql-ws or graphql-transport-ws connection is established. This is particularly useful for authentication and authorization. By default, all connections are accepted.

To manually accept a connection, return strawberry.UNSET or a connection acknowledgment payload. The acknowledgment payload will be sent to the client.

Note that the legacy protocol does not support None /null acknowledgment payloads, while the new protocol does. Our implementation will treat None /null payloads the same as strawberry.UNSET in the context of the legacy protocol.

To reject a connection, raise a ConnectionRejectionError . You can optionally provide a custom error payload that will be sent to the client when the legacy GraphQL over WebSocket protocol is used. 

from typing import Dict
from strawberry.exceptions import ConnectionRejectionError
from strawberry.asgi import GraphQL




class MyGraphQL(GraphQL):
    async def on_ws_connect(self, context: Dict[str, object]):
        connection_params = context["connection_params"]


        if not isinstance(connection_params, dict):
            # Reject without a custom graphql-ws error payload
            raise ConnectionRejectionError()


        if connection_params.get("password") != "secret":
            # Reject with a custom graphql-ws error payload
            raise ConnectionRejectionError({"reason": "Invalid password"})


        if username := connection_params.get("username"):
            # Accept with a custom acknowledgment payload
            return {"message": f"Hello, {username}!"}


        # Accept without a acknowledgment payload
        return await super().on_ws_connect(context)