Lenah

Lenah is an opinionated but flexible REST framework for Chalice. It provides a simple interface to define cloud-native CRUD-based endpoints.

Important

This package is currently in experimental phase. It is not recommended to use this in production currently.

• Free software: MIT license
• Documentation: https://lenah.readthedocs.io.

Features

Restful resource definition: :

from chalice import Chalice

from lenah.resource import RestfulResource, RestfulModelConfiguration
from lenah.models.pynamodb import PynamoDbModelRepository

app = Chalice(app_name='endog')

RestfulResource(app,
                config=RestfulModelConfiguration(
                    resource_name="posts",
                    input_model=BlogRequest,
                    output_model=BlogResponse,
                    db_model_repository=PynamoDbModelRepository(db_model=BlogPost)
                )
)

The definition above will generate the following endpoints:

• GET /v1/posts to list blog posts
• GET /v1/posts/{id} to fetch a specific blog post
• POST /v1/posts to create a new blog post
• PUT /v1/posts/{id} to full update an existing blog post
• PATCH /v1/posts/{id} to json merge patch an existing blog post
• DELETE /v1/posts/{id} to delete an existing blog post
• GET /v1/posts/swagger.json to get the swagger specification for this API (still in development)

The list endpoint accepts pagination_item_count and pagination_page params for pagination.

input_model is a pydantic model that specifies what the request must look like for creating/updating/patching a document. For any invalid request object a lenah.responses.BadRequest is returned.

output_model is a pydantic model that specifies what the data block in the response will look like.

db_model_repository defines the type of database used in the backend. Currently only PynamoDbModelRepository, which is a DynamoDB backend using the PynamoDb library. Custom db repositories can be added by extending the lenah.models.base.ModelRepository class.

Other attributes

Authorizers

An authorizer can be specified through the authorizer attribute. This accepts any built-in Chalice authorizer and applies it to all the generated endpoints.

Custom, per endpoint authorizers can be written by extending the lenah.authorizers.RequestAuthorizer class. The authorizer class must implement the check method. The check method arguments depend on the endpoint in question:

• LIST: request(ChaliceRequest), pagination_item_count(int), pagination_page(str)
• GET: request(ChaliceRequest), id
• UPDATE: request(ChaliceRequest), id, input_model(RequestModel)
• PATCH: request(ChaliceRequest), id
• DELETE: request(ChaliceRequest), id
• CREATE: request(ChaliceRequest), input_model(RequestModel)

For example: :

from lenah.authorizers import RequestAuthorizer, AuthorizationResult

class IsOddId(RequestAuthorizer):
    def check(self, request, id):
        is_odd = id % 2 == 1
        message = 'id is not odd' if not is_odd
        return AuthorizationResult(success=is_odd, message=message)

The above authorizer then can be configured on the RestfulResource through the extra_authorizers attribute.

Like so :

RestfulResource(config=RestfulModelConfiguration(extra_authorizers={RestfulActions.GET, [IsOddId()], ...))

If the authorizer evaluates to success==False a lenah.responses.Unauthorized response is returned.

Credits

This package was created with Cookiecutter and the audreyr/cookiecutter-pypackage project template.