Tornado and Motor async connection

tornado_motor

#!/usr/bin/env python

from tornado import ioloop, web, gen, options
import motor
import json


DEFAULT_TENANT = 'default'  # If Host not found, which default service to Use


class Tenant(object):

    def __init__(self, host, db, **settings):
        self.host = host
        self.db = db
        self.settings = settings


class BaseHandler(web.RequestHandler):

    # store database connections, based on host name, since this is mutable,
    # it'll be shared with all instances and classes
    tenants = {}

    @property
    def central(self):
        return self.settings['db'].central

    @gen.coroutine
    def prepare(self):
        self.tenant = yield self.get_tenant()
        self.db = self.tenant.db

    @gen.coroutine
    def get_tenant(self):
        "Get the db connection based on Host"

        host = self.request.headers['Host']

        tenant = self.tenants.get(host)

        if tenant is not None:
            raise gen.Return(tenant)

        # try to get the host
        data = yield motor.Op(self.central.tenants.find_one, {'name': host})

        # if not found, fallback to default tenant
        if data is None:
            data = yield motor.Op(
                self.central.tenants.find_one, {'name': DEFAULT_TENANT})

        db_host = data['db'].get('host', 'localhost')
        db_port = data['db'].get('host', 27017)

        # TODO Replica set connections

        cx = motor.MotorClient(db_host, db_port)
        conn = yield motor.Op(cx.open)

        tenant_db = conn[data['db']['name']]

        tenant = Tenant(host, tenant_db)
        self.tenants[host] = tenant

        raise gen.Return(tenant)


class MainHandler(BaseHandler):

    @gen.coroutine
    def get(self):
        cursor = self.db.items.find()

        found = []
        while (yield cursor.fetch_next):
            doc = cursor.next_object()
            doc['_id'] = str(doc['_id'])
            found.append(doc)

        self.set_header("Content-Type", "application/json; charset=UTF-8")
        self.finish(json.dumps(found))


db = motor.MotorClient().open_sync()

app = web.Application([
    (r'/', MainHandler),
], db=db, debug=True)

if __name__ == "__main__":
    options.parse_command_line()
    app.listen(8888)
    ioloop.IOLoop.instance().start()