The example has been moved from another repo.

README.md

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+## Task Description
+Write client-server application.
+
+Use case: application which is used in car centers to store information
+about sold cars. At first application will be used in a single car center then
+all centers in town/city/world will use it to store information. It should be
+possible to retrieve info about any sold car by serialNumber.
+Clients pass to server an Object “Car” with following attributes:
+```
+   "ownerName" type="string"
+   "serialNumber" type="uint64"
+   "modelYear" type="uint64"
+   "code" type="string"
+   "vehicleCode" type="string"
+   "engine"
+       "capacity" type="uint16"
+       "numCylinders" type="uint8"
+       "maxRpm" type="uint16"
+       "manufacturerCode" type="char"
+   "fuelFigures"
+       "speed" type="uint16"
+       "mpg" type="float"
+       "usageDescription" type="string"
+   "performanceFigures"
+       "octaneRating" type="uint16"
+       "acceleration"
+         "mph" type="uint16"
+         "seconds" type="float"
+   "manufacturer" type="string"   "model" type="string"
+   "activationCode" type="string"
+```
+Server saves the information persistently.
+
+
+# How to start carstore_app test
+* Setup requirements from src/: `pip3 install -r requirements.txt`.
+* Setup carserver.py from src/: `python3 setup.py install`.
+* Add environment variables from run/env.txt. Fix ports to carserver.py/PostgreSQL for other settings.
+* Run run/server.sh. Fix the options if mentioned ports are unavailable.
+* Run run/test_client.sh. Fix the options if mentioned ports are unavailable.
+
+
+# Source files
+* src/server.py — a socket server which can pick up any response module (an application).
+* src/capstore_app.py — a particular application which have on_response() calling from server.py.
+* src/capstore_model.py — a model (for PostgreSQL) to store the information about cars.
+* src/test_client.py — a program with client which make simple requests to server and prints the server answer.
+* src/create_db.py — code to create database (PostgreSQL) schema. Just for an intermediate test.
+
+
+# Notes
+A Python file with an application must be located in the same directory where carserver.py script starts. For more details see `run/server.sh` please.

app/carstore_app.py

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+"""
+A response module for car store.
+"""
+import json
+from carstore_model import get_car, save_car, delete_car
+
+_FIELD_ACTION = 'action'
+_FIELD_CAR_DATA = 'car_data'
+_FIELD_SERIAL_NUMBER = 'serial_number'
+_ACTION_GET = 'get'
+_ACTION_SAVE = 'save'
+_ACTION_DELETE = 'delete'
+
+
+class ResponseFormatError(Exception):
+	"""
+	It raises when format of client request is wrong.
+	"""
+	pass
+
+
+def on_response(data):
+	"""
+	A response function for carstore application.
+	"""
+	data = json.loads(data)
+	action = data[_FIELD_ACTION]	
+	if action == _ACTION_GET:
+		serial_number = int(data[_FIELD_SERIAL_NUMBER])
+		car_data = get_car(serial_number=serial_number)
+		return car_data
+	elif action == _ACTION_SAVE:
+		car_data = data[_FIELD_CAR_DATA]
+		car_data[_FIELD_SERIAL_NUMBER] = data[_FIELD_SERIAL_NUMBER]
+		save_car(car_data)
+		return True
+	elif action == _ACTION_DELETE:
+		serial_number = int(data[_FIELD_SERIAL_NUMBER])
+		delete_car(serial_number=serial_number)
+		return True
+	else:
+		raise ResponseFormatError('Wrong data format from client.')

app/carstore_model.py

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+"""
+A model for car store.
+"""
+import os
+import decimal
+from sqlalchemy import Column, CheckConstraint
+from sqlalchemy.types import *
+from sqlalchemy.dialects.postgresql.ranges import NUMRANGE
+from sqlalchemy import create_engine
+from sqlalchemy.orm.session import sessionmaker
+from sqlalchemy.ext.declarative import declarative_base
+
+
+_DBPG_HOST = os.environ['CARSTORE__DBPG_HOST']
+_DBPG_PORT = os.environ['CARSTORE__DBPG_PORT']
+_DBPG_NAME = os.environ['CARSTORE__DBPG_NAME']
+_DBPG_USER = os.environ['CARSTORE__DBPG_USER']
+_DBPG_PASSWORD = os.environ['CARSTORE__DBPG_PASSWORD']
+
+
+class UINTConstraintError(Exception):
+	pass
+
+
+def _constraint_uint(name, num_bits):
+	"""
+	To add constraint for uint64/32/16/8.
+	"""
+	if num_bits not in [8, 16, 32, 64]:
+		raise UINTConstraintError('Wrong number of bits.')
+	return CheckConstraint(	'{name} >= 0 AND {name} < {max_num}'.format(name=name, max_num = 2 ** num_bits), 
+							name='{}_positive'.format(name))
+
+
+Base = declarative_base()
+
+
+class Car(Base):
+	"""
+	A car model.
+	"""
+
+	__tablename__ = 'car'
+	# center where car is located
+	serial_number = Column(NUMERIC, nullable=False, primary_key=True)
+	location_center_id = Column(NUMERIC, index=True)
+	owner_name = Column(String)
+	model_year = Column(NUMERIC)
+	code = Column(String)
+	vehicle_code = Column(String)
+	engine__capacity = Column(Integer)
+	engine__num_cylinders = Column(SmallInteger)
+	fuel_figures__speed = Column(Integer)
+	fuel_figures__mpg = Column(Float)
+	fuel_figures__usage_description = Column(String)
+	performance_figures__octane_rating = Column(Integer)
+	performance_figures__acceleration__mph = Column(Integer)
+	performance_figures__acceleration__seconds = Column(Float)
+	manufacturer = Column(String)
+	__table_args__ = (
+		_constraint_uint('location_center_id', 32),
+		_constraint_uint('serial_number', 64),
+		_constraint_uint('model_year', 64),
+		_constraint_uint('engine__capacity', 16),
+		_constraint_uint('engine__num_cylinders', 8),
+		_constraint_uint('fuel_figures__speed', 16),
+		_constraint_uint('performance_figures__octane_rating', 16),
+		_constraint_uint('performance_figures__acceleration__mph', 16)
+	)
+
+
+def get_engine():
+	"""
+	Get SQLAlchemy engine for car DB.
+	"""
+	connect_arg = 'postgresql://{user}:{password}@{host}:{port}/{name}'.format(	\
+		user=_DBPG_USER,
+		password=_DBPG_PASSWORD,
+		host=_DBPG_HOST,
+		port=_DBPG_PORT,
+		name=_DBPG_NAME)
+
+	engine = create_engine(connect_arg)
+	return engine
+
+
+def _get_session(*, autocommit=False):
+	"""
+	Get SQLAlchemy session for car DB.
+	"""
+	engine = get_engine()
+	Session = sessionmaker(bind=engine, autocommit=autocommit)
+	session = Session()
+	return session
+
+
+def _change_json_types(d, supported_json_types, replace_types):
+	"""
+	Core function (without predifined arguments) for fixing model fields to make 
+	it serializable.
+	"""	
+	out_d = {}
+	for key, val in d.items():
+		type_of = type(val)
+		if type_of in supported_json_types:
+			replace_val = d[key]
+			if type_of in replace_types:
+				replace_val = replace_types[type_of](replace_val)
+			out_d[key] = replace_val
+
+	return out_d
+
+
+def _as_json_types(d):
+	"""
+	Fixing (changling/removing) model fields to make it serializable.
+	"""	
+	return _change_json_types(d, (decimal.Decimal, float, int, str), {decimal.Decimal: int})
+
+
+def get_car(*, serial_number):
+	"""
+	Getting a car data by it's serial number.
+	"""	
+	session = _get_session()
+	car_data = session.query(Car).filter_by(serial_number=serial_number).scalar()
+	result = _as_json_types(car_data.__dict__) if car_data is not None else None
+	return result
+
+
+def save_car(car_data):
+	"""
+	Saving the information about a car. All fields are required.
+	"""
+	session = _get_session(autocommit=True)
+	car = Car(**car_data)
+	session.merge(car)
+	session.flush()
+
+
+def delete_car(*, serial_number):
+	"""
+	Delete a car by a serial number (it is used by test).
+	"""
+	session = _get_session(autocommit=True)
+	session.query(Car).filter_by(serial_number=serial_number).delete()
+	session.flush()

run/evn.txt

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+CARSTORE__DBPG_HOST=localhost
+CARSTORE__DBPG_PORT=5432
+CARSTORE__DBPG_NAME=carstore
+CARSTORE__DBPG_USER=user
+CARSTORE__DBPG_PASSWORD=password
+CARSTORE_HOST=localhost
+CARSTORE_PORT=8000

run/server.sh

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+#!/bin/bash
+
+CUR_DIR=$(dirname "$0")
+
+cd $CUR_DIR/../app && \
+carserver.py	--max-connections=32 --buff-size=4096 \
+				--response-module=carstore_app --max-read-time=2000 --poll_timeout=1

run/test_client.sh

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+#!/bin/bash
+
+CUR_DIR=$(dirname "$0")
+
+cd $CUR_DIR/../src && python3 -m pytest test_client.py