def init_database():
# TODO: create a migration script for creating db and its collections
orders = get_client().get_database().orders
inventory = get_client().get_database().inventory
orders.delete_many({})
inventory.delete_many({})
# suppose inventory has 200 items of abc123
inventory.insert_one({"sku": "abc123", "qty": 200})
# suppose orders for abc123 is 0 yet
orders.insert_one({"sku": "abc123", "qty": 0})
def sample_transaction():
init_database()
# https://pymongo.readthedocs.io/en/stable/api/pymongo/client_session.html
# 1. Increments orders by 100
# 2. Decrements inventory by 100
# 3. If either 1 or 2 fails, then the transaction should be aborted
with get_client().start_session() as session:
session.with_transaction(increment_orders_decrement_inventory_callback)
print("Successful transaction!")
def increment_orders_decrement_inventory_callback(session):
orders = session.client.get_database().orders
inventory = session.client.get_database().inventory
# increments 100 items to orders
orders.update_one({"sku": "abc123"}, {"$inc": {"qty": 100}}, session=session)
# decrements 100 items from inventory
inventory.update_one(
{"sku": "abc123", "qty": {"$gte": 0}},
{"$inc": {"qty": -100}},
session=session,
)
- executes sample transaction
- executes sample transaction
- make sure the correct data were created/updated in the database collections
- spins up the mongodb replica set container
- spins up the mongodb replica set and opens pymongo-app's bash
- stops the mongodb and pymongo-app containers