Tartiflette Request SQLAlchemy Session

Middleware for the tartiflette GraphQL server implementation to have a SQLAlchemy Session generated on each server request which is then injected into the resolver context.

1. A provided session is unique to the request.
2. A provided session is shared across queries on a request.
3. Must work for queries, mutations, and subscriptions.

Installation

pip install tartiflette-request-sqlalchemy-session[psycopg2]

Currently only supports PostgreSQL through psycopg. Pull requests for other adaptors are welcome.

Configuration

Note: If you have a working project you won't need to change the Alembic configuration. This is mainly useful for a new project.

Alembic configuration

In env.py add:

from tartiflette_request_sa_session import Database

db_config = Database(
    db='db_name',
    engine='db_engine', # e.g. postgres+psycopg2
    host='db_host',
    password='db_password',
    port='db_port',
    user='db_username',
)
database = Database(**db_config)

Update env.py to use:

config = context.config
config.set_main_option('sqlalchemy.url', database.connection_string)

App.py configuration

This configuration will not usually provide an out of the box working example of a tartiflette aiohttp setup. This should be used as guidance to fit into your configuration.

from tartiflette_middleware import Middleware, server
from tartiflette_request_sa_session import Database, SQLAlchemySessionMiddleware


def run():
   # As with Alembic add:
   db_manager = Database(
      db='db_name',
      engine='db_engine',  # e.g. postgres+psycopg2
      host='db_host',
      password='db_password',
      port='db_port',
      user='db_username',
   )

   # database request-based middleware setup
   sa_middleware = Middleware(
      context_manager=SQLAlchemySessionMiddleware(db_manager=db_manager),
      server_middleware=server.aiohttp,
   )
   # configure app - tweak to fit own configuration
   app = web.Application(middlewares=[
      sa_middleware.middleware,
   ])
   engine = create_engine(
      sdl=os.path.dirname(os.path.abspath(__file__)) + '/sdl',
      modules=[
         # configure as necessary
      ],
   )

   ctx = {
      'db_session_service': sa_middleware.service,
   }
   web.run_app(
      register_graphql_handlers(
         # ... your other settings ...
         executor_context=ctx,
      )
   )

Use

In your resolver you can now access a new session for each request.

Resolver example: query_resolvers.py

async def resolve_new_request(parent, args, ctx, info):
    session = await ctx['db_session_service']()
    u = session.query(YourModel).filter_by(uuid=args['uuid']).first()
    return u

Notes

1. Currently works using "Tartiflette Middleware" which only supports aiohttp. Other servers supporting tartiflette could be supported via pull requests on that project.