Connexion is an open source API first REST framework for Python, built on top of Flask and based on OpenAPI/Swagger, targeted for microservice development. Connexion automagically handles request routing, oauth2 security, request validation and response serialization based on an OpenAPI 2.0 Specification file in YAML, so you don’t have to care about boilerplate anymore. Because it is based on Flask it supports everything that Flask does, including deployment options and extensions. At Zalando we’ve adopted “API First” as one of our key engineering principles, to ensure our API are robust, consistent, general and abstracted from specific implementation and use cases. But when we tried to implement this principle for the first time we were faced with the lack of a python framework to achieve it in a easy fashion - there were several frameworks that produce a swagger definition from the implementation but none that do it the other way around - so we decided to fill that gap. Henning will show how to get started with OpenAPI+Connexion, present some real-world use cases and deployment options such as Kubernetes.

1. PyConWeb 2018
2018-07-01
HENNING JACOBS
@try_except_
API First with
Connexion

2. 2
ZALANDO AT A GLANCE
~ 4.5billion EUR
revenue 2017
> 200
million
visits
per
month
> 15.000
employees in
Europe
> 70%
of visits via
mobile devices
> 23
million
active customers
> 300.000
product choices
~ 2.000
brands
15
countries

3. 3
ZALANDO TECH
~ 2.000
Employees in Tech
> 200
Delivery teams

4. 4
API FIRST

5. 5
API FIRST
• Define REST API before implementation
• API definition is contract between teams
• Includes validation & documentation

6. 6
ZALANDO TECH RADAR

7. 7
ZALANDO TECH RADAR

8. 8
RESTful API
Guidelines
https://github.com/zalando/restful-api-guidelines

11. 11 https://github.com/zalando/intellij-swagger

12. 12 https://github.com/zalando/intellij-swagger

13. 13 https://github.com/zalando/zally

14. 14
Python?

15. 15
Connexion
OpenAPI-first with Python+Flask
https://github.com/zalando/connexion

16. 16
info: {title: "Pet Shop Example API", version: "0.1"}
paths:
/pets:
get:
operationId: app.get_pets
parameters:
- name: animal_type
in: query
type: string
responses:
200:
schema:
type: array
items:
$ref: '#/definitions/Pet'
/pets/{pet_id}:
get:
operationId: app.get_pet
parameters:
- name: pet_id
in: path
type: string
required: true

17. 17
info: {title: "Pet Shop Example API", version: "0.1"}
paths:
/pets:
get:
operationId: app.get_pets
parameters:
- name: animal_type
in: query
type: string
responses:
200:
schema:
type: array
items:
$ref: '#/definitions/Pet'
/pets/{pet_id}:
get:
operationId: app.get_pet
parameters:
- name: pet_id
in: path
type: string
required: true

18. 18
CONNEXION: USAGE
PETS = {}
def get_pets(animal_type=None):
return [pet for pet in PETS.values()
if not animal_type or pet['animal_type'] == animal_type]
def get_pet(pet_id):
pet = PETS.get(pet_id)
return pet or ('Not found', 404)
# ...
app = connexion.App(__name__)
app.add_api('swagger.yaml')
app.run(port=8080, server='gevent')
https://github.com/zalando/connexion

19. 19
QUICKSTART WITH SWAGGER CODEGEN
wget
http://central.maven.org/maven2/io/swagger/swagger-codegen-cli/2.3.1/swagger
-codegen-cli-2.3.1.jar -O swagger-codegen-cli.jar
java -jar swagger-codegen-cli.jar generate -i swagger.yaml -l python-flask
docker build -t myapp .
docker run -it -p 8080:8080 myapp
Swagger's
"python-flask" is
actually Connexion!
https://github.com/swagger-api/swagger-codegen

20. 20
CONNEXION FEATURES
• Path, query and body params mapped to Python args
• Bundled Swagger UI (served on /ui/ path)
• Automatic JSON serialization
• Schema validation for HTTP request body and query params:
• required object properties
• primitive types (string, integers, etc)
• date/time values
• string lengths
• min/max values
• regular expressions
https://github.com/zalando/connexion

21. 21
DEPLOYMENT
CONSIDERATIONS

22. 22
SWAGGER CODEGEN..
docker run -it -p 8080:8080 swagger-codegen-server
... OAuth2 token info URL missing. **IGNORING SECURITY REQUIREMENTS**
* Serving Flask app "__main__" (lazy loading)
* Environment: production
WARNING: Do not use the development server in a production environment.
Use a production WSGI server instead.
* Debug mode: off
* Running on http://0.0.0.0:8080/ (Press CTRL+C to quit)

23. 23
CONSIDERATIONS
• WSGI server?
• Runtime?
• Target environment?
• High availability?
• Performance?

24. 24
CONSIDERATIONS
• WSGI server? gevent
• Runtime? Docker, image ~74MiB
• Target environment? Kubernetes
• High availability? multiple pods, readinessProbe
• Performance? load test
https://github.com/hjacobs/connexion-example-redis-kubernetes

25. 25
EXAMPLE #1
https://github.com/hjacobs/connexion-example-redis-kubernetes

26. 26
KILLING REDIS
kubectl get pod
NAME READY STATUS RESTARTS AGE
connexion-example-67c64766f5-rgmmz 1/1 Running 0 55s
connexion-example-67c64766f5-rwjt7 1/1 Running 1 1h
connexion-example-redis-0 0/1 Terminating 1 1h
https://github.com/hjacobs/connexion-example-redis-kubernetes

27. 27
RESILIENCE
https://github.com/hjacobs/connexion-example-redis-kubernetes
Rolling deployment
Redis downtime

28. 28
EXAMPLE #2: ZALANDO AWS CREDENTIALS
https://github.com/zalando-stups/aws-credentials-service

29. 29
CONNEXION IN ZALANDO

30. 30
REAL WORLD SERVICE

31. 31
OPEN SOURCE
Zalando's RESTful API Guidelines
https://github.com/zalando/restful-api-guidelines
IntelliJ IDEA Swagger Editor Plugin
https://github.com/zalando/intellij-swagger
Zally API Linter
https://github.com/zalando/zally
Connexion
https://github.com/zalando/connexion
Connexion Examples
https://github.com/hjacobs/connexion-example
https://github.com/zalando-stups/aws-credentials-service

32. QUESTIONS?
HENNING JACOBS
HEAD OF
DEVELOPER PRODUCTIVITY
henning@zalando.de
@try_except_
Illustrations by @01k