Extension system

Ariadne implements simple extension system that allows developers to inject custom python logic into the query execution process.

At the moment adding extensions to subscriptions is not supported.

Enabling extensions

To enable extensions, initialize GraphQL app with extensions parameter. This parameter accepts list of extensions:

from ariadne.asgi import GraphQL

from .schema import schema
from .extensions import MyExtension


app = GraphQL(
    schema,
    extensions=[MyExtension]
)

Alternatively, if your extension depends on request or should be enabled conditionally, you can provide callable that will return extensions that should be used:

from ariadne.asgi import GraphQL

from .schema import schema
from .extensions import MyExtension


def get_extensions(request, context):
    if request.headers.get("x-enable-my-extension"):
        return [MyExtension]
    return None


app = GraphQL(
    schema,
    extensions=get_extensions
)

Custom extension example

Let's create simple extension that measures query execution time, and appends this time to query's result.

All extensions should extend special base class named Extension, importable from ariadne.types:

from ariadne.types import Extension


class QueryExecutionTimeExtension(Extension):
    ...

Our extension will measure the query execution time. This means we need to measure the time of two events, request start and creation of JSON response:

import time

from ariadne.types import Extension


class QueryExecutionTimeExtension(Extension):
    def __init__(self):
        self.start_timestamp = None
        self.end_timestamp = None

    def request_started(self, context):
        self.start_timestamp = time.perf_counter_ns()

    def format(self, context):
        if self.start_timestamp and self.end_timestamp:
            return {
                "execution": time.perf_counter_ns() - self.start_timestamp
            }

See Extension reference for the list of available events.

WSGI extension implementation

If your GraphQL server is deployed using WSGI, you can't use Extension as base class for your extensions. Use ExtensionSync which implements a synchronous resolve instead:

from ariadne.types import ExtensionSync as Extension


class QueryExecutionTimeExtension(Extension):
    ...