Configuration¶

Configuration versus Environment variable¶

There are three configuration levels:

Project config,
Execution config,
Application config.

Project configuration

Project configuration is related to how the team works and how deployment should be done. This description is done by a project configuration file: project.cws.yml. This project configuration file describes the commands and options associated to the project.

Execution configuration

As for the Twelve-Factor App : “The twelve-factor app stores config in environment variables. Env vars are easy to change between deploys without changing any code;”. Using environment variables is highly recommanded to enable easy code deployments to differents systems: Changing configuration is just updating variables in the configuration in the CI/CD process.

Application configuration

At last : “application config does not vary between deploys, and so is best done in the code.”

That’s why entries are defined in the code. The link from entry to function is always the same.

In Flask, there is only the concept of application configuration as the excution configuration if out of is scope (mainly associated to the USWGI server).

In CoWorks, we use the concept of stage for execution configuration deployed in lambda variables.

Project configuration¶

Stage is a key concept for the deployment. Stages are defined thru the concept of workspace in terraform, stage for AWS API Gateway and variables of AWS Lambda.

Workspace definition¶

The workspace value will correspond to the CWS_STAGE variable value.

You certainly may need to attach environment variables to your project. Of course thoses variables may depend on the stage status. How? You just need to create and specify custom environment files.

CoWorks uses dotenv files to allow you to define your environment variables for stages. Dotenv file are named .env and .env_{CWS_STAGE}.

As example you can deploy the specific stage dev of the microservice app defined in the app python file in the folder tech:

$ CWS_STAGE=dev deploy

The environment variables accessible from the lambda must be defined in .env and .env_dev.

Project configuration file¶

A project configuration file is a YAML file containg the command and options defined for the project.

Example¶

Example of a project.cws.yml file:

version: 3
commands:
  run:
    host: localhost
    port: 5000
  deploy:
    class: fpr.cws.deploy.fpr_deploy
    profile_name: fpr-customer
    bucket: coworks-microservice
    customer: neorezo
    project: cws_utils_mail
    layers:
      - arn:aws:lambda:eu-west-1:935392763270:layer:coworks-0.6.8
workspaces:
  dev:
    commands:
      run:
        port: 8000
      deploy:
        layers:
          - arn:aws:lambda:eu-west-1:935392763270:layer:coworks-dev

Structure¶

**Project Configuration File Structure**¶
Field	Value	Description
version	3	YAML syntax version
commands	Command Structure List (below)	List of commands
workspaces	Workspace Structure List (below)	List of workspaces where commands are redefined

**Command Structure**¶
Command Name	Command Option	Project Value
run
	host	localhost
	port	5000

**Workspace Structure**¶
Workspace Name	Command Name	Command Option	Project Value
dev
	run
		port	8000

Authorization¶

By default all TechMicroService have access protection defined in the microservice itself and defined thru a token basic authentication protocol based on HTTP Authentification

Class control¶

For simplicity, we can define only one simple authorizer on a class. The authorizer may be defined by the method token_authorizer.

from coworks import TechMicroService

class SimpleExampleMicroservice(TechMicroService):

        def token_authorizer(self, token):
                return True

If the method returns True all the routes are allowed. If it returns False all routes are denied.

Using the APIGateway model, the authorization protocol is defined by passing a token ‘Authorization’. The API client must include it in the header to send the authorization token to the Lambda authorizer.

from coworks import TechMicroService

class SimpleExampleMicroservice(TechMicroService):

        def token_authorizer(self, token):
                return token == os.getenv('TOKEN')

To call this microservice, we have to put the right token in headers:

curl https://zzzzzzzzz.execute-api.eu-west-1.amazonaws.com/my/route -H 'Authorization: thetokendefined'