lymph-sqlalchemy

This is a library is a basic wrapper around sqlalchemy that provides an easy way to write an interface, integrate logging and helps in testing.

Store

The lymph.sqlalchemy.store.Store class is a basic wrapper around sqlalchemy, it configures the engine and gives an interface to sessions.

from lymph.sqlalchemy.store import Store
store = Store('postgresql://postgres/lymph-test-sqlalchemy')
# Access the engine
engine = store.engine
engine.execute('SELECT 1')

# The sessions are context managers
with store.get_session() as session:
    session.add(user)

You can pass all of the engine args to the Store, they would be passed on when creating the engine.

Defining Models

The recommended way of defining your models is by first creating an sqlalchemy declarative base class and then define your models like any normal sqlalchemy models:

from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class User(Base):
     __tablename__ = 'users'

     id = Column(Integer, primary_key=True)
     name = Column(String)

IMPORTANT: Please put the Base class in the same python module as the models, else you may have some import problems.

Interface

The lymph.sqlalchemy.interface.StoreInterface class uses the the lymph config to configure a store instance.

An example config for a StoreInterface looks like this, it has a dependency on store.

import lymph
from lymph.sqlalchemy.interface import StoreInterface

class UserInterface(StoreInterface):

    @lymph.rpc()
    def create_user(self, data):
        user = User(**data)
        with self.store.get_session() as session:
            session.add(user)

dependencies:
    store:
        class: lymph.sqlalchemy.store:Store
        uri: postgresql://postgres/users
        pool_size: 5
        max_overflow: 10
        pool_timeout: 30
        base: dhh.users.models:Base

interfaces:
    restaurants:
        class: UserInterface
        store: dep:store

Testing

The library provides a lymph.sqlalchemy.testing.StorageInterfaceTest to help you write your unittests. You would extend this class by providing it your own database config and your service interface.

The class would create the database on setupClass and it would create the tables and the models that you provided as fixtures in setUp method of the test case.

In the teardown this class would drop all the tables.

from lymph.sqlalchemy.testing import StorageInterfaceTest


class UserInterfaceTest(StorageInterfaceTest):

    def get_fixtures(self):
        self.user = User(name='Test')
        self.user_2 = User(name='Test 2')
        return [self.user, self.user_2]

    def test_get_user(self):
        user = self.client.get(pk=self.user.id)
        user_2 = self.client.get(pk=self.user_2.id)
        self.assertEqual(user.id, self.user.id)
        self.assertEqual(user_2.id, self.user_2.id)

Command Line Interfaces

This library provides a couple of cli to make the workflow easiers.

init-db command would create all the tables for all models that are defined using the library's Base

$lymph init-db -c <config>.yml

dependencies:
    store:
          class: lymph.sqlalchemy.store:Store
          base: dhh.users.models:Base

sql-shell command would give you a shell with a store instance already configured.

$LYMPH_NODE_CONFIG=`pwd`/.lymph.yml lymph sql-shell -c <config>.yml