restio Framework
Project description
restio
restio is a Python ORM-like framework that manages relational data coming from remote REST APIs, in a similar way that is done for databases.
Some of the advantages of using restio in comparison with raw REST Client APIs:
- Clear decoupling between models and data access logic.
- Client-side caching of models and queries.
- Improved performance for nearly all operations with native use of
asyncio
. - Type-checking and data validation.
- Model state management.
- Rich relational models and dependency management.
- Fully integrated with type-hinting.
Installation
Requirements
- Python 3.7+
Pip
You can install the latest pre-release version of restio as a dependency to your project with pip:
pip install --pre restio
Practical Example
A typical REST Client API implemented with restio looks like the following:
from __future__ import annotations
from typing import Dict, Any, Optional
import aiohttp
import json
from restio.dao import BaseDAO
from restio.fields import ModelField, IntField, StrField
from restio.model import BaseModel
from restio.session import Session
# Model definition - this is where the relational data schema is defined
class Employee(BaseModel):
key: IntField = IntField(pk=True, allow_none=True, frozen=FrozenType.ALWAYS)
name: StrField = StrField()
age: IntField = IntField()
address: StrField = StrField(default="Company Address")
boss: ModelField[Optional[Employee]] = ModelField("Employee", allow_none=True)
# Data access object definition - teaches restio how to deal with
# CRUD operations for a relational model
class EmployeeDAO(BaseDAO[Employee]):
client_session: aiohttp.ClientSession = aiohttp.ClientSession(raise_for_status=True)
url = "http://remote-rest-api-url"
async def get(self, *, key: int) -> Employee:
employee_url = f"{self.url}/employees/{key}"
result = await self.client_session.get(employee_url)
employee_data = await result.json()
# asks the current session to retrieve the boss from cache or
# to reach to the remote server
boss = await self.session.get(Employee, key=employee_data["boss"])
return self._map_from_dict(employee_data, boss)
async def add(self, obj: Employee):
employees_url = f"{self.url}/employees"
payload = json.dumps(self._map_to_dict(obj))
response = await self.client_session.post(employees_url, data=payload.encode())
location = response.headers["Location"]
key = location.split("/")[-1]
# update the model with the key generated on the server
obj.key = key
@staticmethod
def _map_from_dict(data: Dict[str, Any], boss: Employee) -> Employee:
return Employee(
key=int(data["key"]),
name=str(data["name"]),
age=int(data["age"]),
address=str(data["address"]),
boss=boss
)
@staticmethod
def _map_to_dict(model: Employee) -> Dict[str, Any]:
return dict(
name=model.name,
age=model.age,
address=model.address,
boss=model.boss.key
)
Once Models
and Data Access Objects
(DAOs) are provided, you can use Sessions
to operate the Models
:
# instantiate the Session and register the DAOs EmployeeDAO
# to deal with Employee models
session = Session()
session.register_dao(EmployeeDAO(Employee))
# initialize session context
async with session:
# retrieve John Doe's Employee model, that has a known primary key 1
john = await session.get(Employee, key=1) # Employee(key=1, name="John Doe", age=30, address="The Netherlands")
# create new Employees in local memory
jay = Employee(name="Jay Pritchett", age=65, address="California")
manny = Employee(name="Manuel Delgado", age=22, address="Florida", boss=jay)
# at the end of the context, `session.commit()` is called automatically
# and changes are propagated to the server
Overview
When consuming remote REST APIs, the data workflow used by applications normally differs from the one done with ORMs accessing relational databases.
With databases, it is common to use transactions to guarantee atomicity when persisting data on these databases. Let's take a Django-based application example of a transaction (example is minimal, fictitious and adapted from https://docs.djangoproject.com/en/3.1/topics/db/transactions/):
from django.db import DatabaseError, transaction
from mylocalproject.models import Person
def people():
try:
with transaction.atomic():
person1 = Person(name="John", age=1)
person2 = Person(name="Jay", age=-1) # mistake!
person1.friends.add(person2)
person1.save()
person2.save()
except DatabaseError as err:
# rollback is already done here, no garbage left on the database
print(err) # Person can't have age smaller than 0
For remote REST APIs, guaranteeing atomicity becomes a difficult job, as each call to the remote API should be atomic. If the same code above was to be called to a REST API client, you would typically see the following:
from restapiclient import ClientAPI, Person
client = ClientAPI()
def people():
person1: Person = client.create_person(name="John", age=1) # ok
person2: Person = client.create_person(name="Jay", age=-1) # error, exit
person1.friends.add(person2)
client.update_person(person1)
In this case, not only the calls to the server are done synchronously, but the data validation of person2
would be done too late (either by the client API or the server). Since person1
was already added, now we have garbage left on the remote server.
restio is designed to optimize this and other cases when interacting with REST APIs. It does it in a way that it is more intuitive for developers that are already familiar with ORMs and want to use a similar approach, with similar benefits.
Please visit the official documentation for more information.
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