PyMacaron

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A python microservice framework

Reference:

Overview
Get started
Write an API specification
Implement your API
Deploy to AWS
JWT authentication
Configuration
Error handling
Asynchronous execution
Database serialisation
Testing

Database Support

PyMacaron lets you transparently serialise API objects to and from an underlying database.

Currently, only Amazon DynamoDB is supported as a serialisation backend.

Serialisation with DynamoDB

pymacaron-dynamodb is a an extension of pymacaron that lets you add serialisation between your API objects and Amazon’s Dynamodb.

Install

pip install pymacaron-dynamodb

And add it to your microservice dependencies:

echo 'pymacaron-dynamodb' >> requirements.txt

API definition

Here is an example adding serialisation to a Profile object, where serialising is handled by the class ‘myserver.db.profile.PersistentProfile’.

In the Swagger file defining your API, add the ‘x-persist’ attribute to the objects you want to serialise:


  Profile:
    type: object
    description: A profile that can persist to DynamoDB
    x-persist: myserver.db.profile.PersistentProfile
    properties:
      profile_id:
        type: string
        format: profile_id
        description: Unique Profile ID.

In your code

Now create the ‘myserver.db.profile’ module containing the class ‘PersistentProfile’:


from pymacaron_dynamodb import PersistentSwaggerObject, DynamoDBItemNotFound

class PersistentProfile(PersistentSwaggerObject):
    api_name = 'myserver'
    model_name = 'Profile'
    table_name = 'some-dynamodb-table-name'
    primary_key = 'profile_id'

# And use PersistentProfile as in the examples below:

def profile_exists(profile_id):
    """Return true if this profile exists"""
    return PersistentProfile.get_table().has_item(profile_id=profile_id)

def get_profile(profile_id):
    """Retrieve profile from dynamodb or an exception if profile does not exist"""
    try:
        p = PersistentProfile.load_from_db(profile_id)
        return p
    except DynamoDBItemNotFound as e:
        raise MyOwnException("Profile %s does not exist" % profile_id)

Loading and saving profiles can now be done as follows:

from myserver.db.profile import get_profile, profile_exists
from pymacaron.exceptions import PyMacaronException

class UserNotFoundError(PyMacaronException):
    code = 'USER_NOT_FOUND'
    status = 404

def my_endpoint(user_id):

    if not profile_exists(user_id):
       raise UserNotFoundError('This user does not exists')

    profile = get_profile(user_id)

    # Just to illustrate updating the DynamoDB profile:
    profile.view_count = profile.view_count + 1
    profile.load_to_db()

    # Return profile as a json API object
    return profile