Lightweight and powerful wsgi rest framework for rapid building applications based on wsgi servers.
Project description
Chocs
Chocs is a modern HTTP framework for building AWS HTTP API/REST API and WSGI compatible applications. Chocs aims to be small, expressive, and robust. It provides an elegant API for writing fault-proof, extensible microservices.
Features
- AWS Serverless integration
- Open api integration
- Elegant and easy API
- No additional bloat like built-in template engines, session handlers, etc.
- Compatible with all WSGI servers
- Loosely coupled components which can be used separately
- Multipart body parsing
- Graceful error handling
- HTTP middleware support
- Fast routing
Installation
pip install chocs
Usage
Quick start
from chocs import Application
from chocs import HttpRequest
from chocs import HttpResponse
from chocs import serve
http = Application()
@http.get("/hello/{name}")
def hello(request: HttpRequest) -> HttpResponse:
return HttpResponse(f"Hello {request.path_parameters.get('name')}!")
serve(http)
Keep in mind that the
serve()
function is using thebjoern
package, so make sure you included it in your project dependencies before using it. You are able to use any WSGI compatible server.
Running application with Gunicorn (or any other WSGI server)
# myapp.py
from chocs import Application
from chocs import HttpRequest
from chocs import HttpResponse
from chocs import create_wsgi_handler
http = Application()
@http.get("/hello/{name}*")
def hello(request: HttpRequest) -> HttpResponse:
return HttpResponse(f"Hello {request.path_parameters.get('name')}!")
app = create_wsgi_handler(http, debug=False)
gunicorn -w 4 myapp:app
Running application in AWS Lambda (Http api or rest api)
handler.py
import logging
from chocs import HttpRequest
from chocs import HttpResponse
from chocs import Application
logger = logging.getLogger()
logger.setLevel(logging.INFO)
http = Application()
@http.get("/hello/{name}")
def hello_handler(request: HttpRequest) -> HttpResponse:
logger.info("Hello AWS!")
logger.info(request.attributes.get("aws_context"))
logger.info(request.attributes.get("aws_event"))
return HttpResponse(f"Hello {request.path_parameters.get('name')}")
__all__ = ["hello_handler"]
serverless.yml
service: aws-hello-name
provider:
name: aws
runtime: python3.8
plugins:
- serverless-python-requirements
custom:
pythonRequirements:
dockerizePip: true
functions:
hello_name:
handler: handler.hello_handler
events:
- httpApi:
method: GET
path: /hello/{name}
serverless deploy
Routing
Chocs is shipped with a built-in routing module. The easiest way to utilise chocs' routing is to use chocs.router
object.
chocs.router
is an instance of the module's internal class chocs.application.Application
, which provides a simple API
where each function is a decorator corresponding to an HTTP method.
from chocs import Application, HttpResponse, HttpRequest
http = Application()
@http.get("/hello")
def hello(req: HttpRequest) -> HttpResponse:
...
The above example will assign the hello function to handle a GET /hello
request.
Available methods:
delete
get
head
options
patch
post
put
trace
Parametrized routes
Routes can contain parameterised parts. Parameters must be enclosed within {
and }
.
from chocs import Application
http = Application()
@http.get("/pet/{id}")
def hello():
...
Will match the following URIs:
/pet/1
/pet/abc
/pet/abc1
Wildcard routes
Asterisks (*
) can be used in the route's pattern to match any possible combination. Keep in mind that routes which
do not contain wildcards are prioritised over routes with wildcards.
from chocs import Application
http = Application()
@http.get("/pet/*", id)
def hello():
...
The above example will match following URIs:
/pet/a
/pet/a/b/c
/pet/12jd/fds
Route groups
Chocs supports route groups. Route groups is implemented through context lib interface. If you need to split your application in smaller chunks with standalone req/res handlers consider the following example:
from threading import Thread
from chocs.wsgi import serve
from chocs import Application
from chocs import HttpRequest
from chocs import HttpResponse
main_app = Application()
with main_app.group("/users/{id}") as user_module:
@user_module.post("/profile_picture") # POST /users/{id}/profile_pictures
def create_profile_picture(request: HttpRequest) -> HttpResponse:
...
@user_module.get("/profile_picture") # GET /users/{id}/profile_pictures
def get_profile_picture(request: HttpRequest) -> HttpResponse:
...
@user_module.get("/badges") # GET /users/{id}/badges
def badges(request: HttpRequest) -> HttpResponse:
...
with main_app.group("/payments") as payment_module:
@payment_module.get("/analytics") # GET /payments/analytics
def get_analytics(request: HttpRequest) -> HttpResponse:
...
if __name__ == '__main__':
def wsgi_user_module():
serve(user_module, port=8081)
def wsgi_payment_module():
serve(payment_module, port=8082)
Thread(target=wsgi_user_module).start()
payment_module()
The above example shows how to run two different modules, which support their own routes on two different ports in the one process.
Middleware
Middleware are functions or classes that inherit chocs.Middleware
. Middlewares have access to the request object
and the next
function which can be used to control middleware stack flow. Successful middleware execution should call
the next
function which accepts a chocs.HttpRequest
instance and returns chocs.HttpReponse
.
Middlewares can perform various tasks:
- Making changes in request/response objects ending
- Validating input data
- Authenticating users
- End request-response cycle
- Connecting to external data sources
Integration with openapi
To provide automatic validation for your request based on open api specification,
use chocs.middleware.OpenApiMiddleware
middleware bundled with chocs:
from chocs.middleware import OpenApiMiddleware
from chocs import Application, HttpRequest, HttpResponse
from os import path
from dataclasses import dataclass
# absolute path to file containing open api documentation; yaml and json files are supported
openapi_filename = path.join(path.dirname(__file__), "/openapi.yml")
# instantiating application and passing open api middleware
app = Application(OpenApiMiddleware(openapi_filename, validate_body=True, validate_query=True))
# defining our dataclass for better type support
@dataclass()
class Pet:
id: str
name: str
# the registered route must correspond to open api route within `path` section.
# if request body is invalid the registered function will not be executed
@app.post("/pets") # `parsed_body` parameter can be used to map request to certain type
def create_pet(request: HttpRequest) -> HttpResponse:
try:
pet = Pet(**request.parsed_body)
except TypeError:
return HttpResponse(status=400)
return HttpResponse(pet.name)
Complete integration example can be found here
Chocs automatically validates:
- request body,
application/json
header must be present for successful validation - query string parameters
- request headers
Mapping request payload to custom dataclasses
from chocs.middleware import ParsedBodyMiddleware
from chocs import Application, HttpRequest, HttpResponse
from dataclasses import dataclass
# You can define whether to use strict mode or not for all defined routes.
app = Application(ParsedBodyMiddleware(strict=False))
@dataclass()
class Pet:
id: str
name: str
@app.post("/pets", parsed_body=Pet, strict=False) # you can also override default strict mode
def create_pet(request: HttpRequest) -> HttpResponse:
pet: Pet = request.parsed_body
assert isinstance(pet, Pet)
return HttpResponse(pet.name)
Note: By default chocs works in a strict mode, which means when you map request data to your object
__init__
method is called. To override this behaviour setstrict
property to false:@app.post("/pets", parsed_body=Pet, strict=False)
or usestrict=False
when initialising middleware:ParsedBodyMiddleware(strict=False)
Handling validation errors with custom middleware
By default, if validation fails users will see 500 response
. This behavior can be changed if custom middleware that
catches validation errors is defined and used in application.
Defining and using a custom middleware
The following code defines simple function middleware to catch validation errors when they appear and notifies users:
from chocs.middleware import OpenApiMiddleware
from chocs.json_schema.errors import ValidationError
from chocs import Application, HttpRequest, HttpResponse
from dataclasses import dataclass
import json
from typing import Callable
from os import path
openapi_filename = path.join(path.dirname(__file__), "/openapi.yml")
# middleware must always accept two parameters; HttpRequest and Callable and return HttpResponse
def handle_errors(request: HttpRequest, next: Callable) -> HttpResponse:
try:
return next(request) # we pass request further to middleware pipeline
except ValidationError as error: # if exception is thrown it is caught here and new response is generated instead
json_response = {
"code": error.code,
"message": str(error),
}
return HttpResponse(json.dumps(json_response), status=422)
# error handling middleware must go before open api one to catch errors thrown inside open api middleware
app = Application(handle_errors, OpenApiMiddleware(openapi_filename))
@dataclass()
class Pet:
id: str
name: str
@app.post("/pets", parsed_body=Pet)
def create_pet(request: HttpRequest) -> HttpResponse:
assert isinstance(request.parsed_body, Pet)
pet = request.parsed_body
return HttpResponse(pet.name)
Full working example can be found inside examples directory
Request
chocs.Request
object is an abstraction around WSGI's environment and wsgi.input
data with handy interface
to ease everyday work.
chocs.Request.headers:chocs.HttpHeaders (read-only)
Keeps parsed headers in dict-like object.
chocs.Request.body:io.BytesIO
Raw body data
chocs.Request.parsed_body:chocs.HttpMessage
Depending on the content type it could be one of the following:
chocs.FormHttpMessage
chocs.JsonHttpMessage
chocs.MultipartHttpMessage
chocs.YamlHttpMessage
chocs.Request.as_dict(): dict
Tries to convert request body to a dict and returns it.
Note this will only work with json and yaml content types.
chocs.Request.as_str(): str
Returns request content as a string.
chocs.Request.cookies:typing.List[chocs.HttpCookie]
Request's cookies
chocs.Request.method:chocs.HttpMethod
The request's method
chocs.Request.path:str
The request's path
chocs.Request.query_string:chocs.HttpQueryString
A dict like object with parsed query string with JSON forms support
chocs.Request.path_parameters:dict
Matched route parameters, for example when /users/john
matches the /users/{name}
route, parameters will contain a
name
key with a value of john
chocs.Request.attributes:dict
Other environmental or custom attributes attached to the request object, eg.: aws_event
or aws_context
when running chocs app as aws lambda.
Response
chocs.Response
object is a part of request-response flow and it is required to be returned by all functions
decorated with router.*
method. Instance of the response class is recognised by chocs.Application
and used to
generate real response served to your clients.
chocs.Response.body: io.BytesIO
Body served to server's clients.
chocs.Response.status_code: chocs.HttpStatus
Valid response code, instance of chocs.HttpStatus
enum can be used or just a status code's number.
chocs.Response.cookies:chocs.HttpCookieJar
Response's cookies
chocs.Response.write(body: Union[bytes, str, bytearray])
Write bytes to response body
chocs.Response.close()
Makes body non-writable.
chocs.Response.writable: bool
Indicates whether response's body is writable.
chocs.Response.parsed_body:chocs.HttpMessage
Depending on the content type it could be one of the following:
chocs.FormHttpMessage
chocs.JsonHttpMessage
chocs.MultipartHttpMessage
chocs.YamlHttpMessage
chocs.Response.as_dict(): dict
Tries to convert response body to a dict and returns it.
Note this will only work with json and yaml content types.
chocs.Response.as_str(): str
Returns response content as a string.
Working with cookies
chocs.HttpCookieJar
object takes care of cookie handling. It can be accessed in dict-like manner, when item is requested,
instance of chocs.HttpCookie
is returned to user.
Cookies can be set either by passing string value to the chocs.CookieJar
's key, or by calling chocs.CookieJar.append
method which accepts instance of chocs.Cookie
.
Reading client cookies
Cookies can be easily accessed from chocs.Request.cookies
object which is injected as a parameter to each function
registered as route handler. Consider the following example:
from chocs import HttpRequest
from chocs import HttpResponse
from chocs import Application
from chocs import serve
http = Application()
@http.get("/cookies")
def read_cookies(request: HttpRequest) -> HttpResponse:
message = "Hello"
if "user_name" in request.cookies:
message += f", {str(request.cookies['user_name'])}"
message += "!"
return HttpResponse(body=message)
serve(http)
Setting cookies
from datetime import datetime
from chocs import HttpCookie
from chocs import HttpRequest
from chocs import HttpResponse
from chocs import Application
from chocs import serve
http = Application()
@http.get("/cookies")
def read_cookies(request: HttpRequest) -> HttpResponse:
response = HttpResponse(body="Hi! I have baked some cookies for ya!")
response.cookies['simple-cookie'] = "Simple cookie for simple people"
response.cookies.append(HttpCookie("advanced-cookie", "This cookie will expire in 2021-01-01", expires=datetime(2021, 1, 1)))
return response
serve(http)
Contributing
Prerequisites
- libev
- python 3.8
- docker
Installation
poetry install
Running tests
poetry run pytest
Linting
poetry run black .
poetry run isort .
poetry run mypy .
PR
Project details
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