WSGI Microservice Middleware

This little library contains middlewares to help quickly turn wsgi apps (e.g., flask, django, bottle, tornado, pyramid) into production-ready microservices for integration into a kubernetes cluster. These middelewares set up to be configurable warfrom environment variables in accordance with the twelve-factor app methodology.

Middlewares in this package include:

• CORS
• Request Id

This project spun out of development for the Presalytics as way to quickly port code across various microserivces built on wsgi-supported frameworks.

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Installation

This project requires python 3.5+. It is best installed fromt he pypi package repository via pip.

pip install wsgi_microservice_middleware

The latest branch of this package can also be installed from git:

pip install git+https://github.com/presalytics/WSGI-Microservice-Middleware

Configuration

Package configuration is best done by adding configuration values via environment varialble. This package uses the environs package to load the following values from the system environment or a .env file in the the working directory:

• CORS_ALLOWED: Comma-separated string of domain names that will from which CORS requests can be made. Is empty by default

• REQUEST_ID_HEADER: The http request header containing a the request-id to including in logs. If not supplied, defaults to X-Request-Id.

Usage

These middleware are applied by wrapping the wsgi application object in you code by the middleware class. Examples below:

• Flask:

  # app.py
  from flask import Flask
  from wsgi_microservice_middleware.cors import CORSMiddleware
  
  app = Flask(__name__)
  app.wsgi_app = CORSMiddleware(app.wsgi_app) # Middleware applied here
  app.run(...) 

• Django:

  # wsgi.py
  from django.core.wsgi import get_wsgi_application
  from wsgi_microservice_middleware.request_id import RequestIdMiddleware
  
  application = get_wsgi_application()
  application = RequestIdMiddleware(application) # Middleware applied here

Modules

CORS

Adds CORS headers to the responses of request that originate from domains in the CORS_ALLOWED environment variable. CORS_ALLOWED should reside in the environment as a comma-separated string of domain names.

Request Id

Implements Request Id handling for requests that need to be tracked accross multiple microservices and searched in log records. The RequestIdMiddleware class.

To extend the request Id to your application logs, incorporate the RequestIdFilter into your logging configuration. the best way to do this is to use logging.config.dictConfig to apply the filter to all of your handlers:

# log_config.py
from logging.config import dictConfig
from wsgi_microservice_middleware.request_id import RequestIdFilter


dictConfig({
    'version': 1,
    'filters': {
        'request_id_filter' : {
            '()': RequestIdFilter,  # RequestIdFilter.filter(self, record) called with each log entry
        }

    },
    'formatters': {'default': {
        'format': '%(asctime)s - %(threadName)s - %(name)s - %(levelname)s - %(request_id)s -  %(message)s',
    }},
    'handlers': {
        'wsgi': {
            'class': 'logging.StreamHandler',
            'formatter': 'default',
            'filters': ['request_id_filter']  # add this filter to each handler
        },
    },
    'root': {
        'level': 'DEBUG',
        'handlers': ['wsgi']
    }
})

If your microservice makes requests to other microservices, you can call the current_request_id() method to get the current request id and incorporate it into your request headers.

Contributing

We'd love your help! Open an issue at the github repo. Or even better, you can fork the repo and we'll merge your improvements.