service-systemic-showcase

Main bits

• Separation of concerns using the Hexagonal Architecture (Ports and Adapters) approach.
• Components and sub-components single responsibility.
• Components and sub-components versioning.
• Multiples business logic workflows.
• Systemic ecosystem npm handy modules (e.g. systemic-rabbitmq - systemic-mongdb).

Workflows

The service is intended to implement a simple businees logic in charge of dealing with the message entity. Two are the main workflows managed by the businnes logic of the service:

1. asynchronous
   1. the service is subscribed to the rabbitmq bus.
   2. the service receives a new message in the form of { id: '1', text: 'Hello World!' }.
   3. the service stores the message in a mongodb database (collection: messages) in the form of { id: '1', text: 'Hello World!', receptionTimestamp: '2020-05-16T14:41:20.055Z' }.
2. synchronous
   1. the service exposes a set /vx/message/{id} endpoints (v1 and v2).
   2. the service reaches out the mongodb store in order to retrieve the requested message.
   3. the service gives back a different response according to the different endpoints version:
      1. /v1/message/1 --> { id: '1', text: 'hello world!' }.
      2. /v2/message/1 --> { id: '1', text: 'HELLO WORLD!', receptionTimestamp: '2020-05-16T14:41:20.055Z' }.

COMPONENTS

Stored into the /components folder. Each one of them comes with an index.js file that acts as a manifest telling systemic how to wire components but most important in which order starting and stopping them.

Hierarchy

• app: service-systemic-showcase root system (component).
• logger: logging utility component.
• express: express server component.
• config: configuration manager component.
• routes: express server routes component.
  • routes.admin: admin api routes sub-components.
  • routes.api.v1: api v1 routes sub-components.
  • routes.api.v2: api v2 routes sub-components.
• controller: orchestrator of components, handles the core logic of the Hexagon Architecture.
  • controller.api.v1: exposes the v1 business logic needed to manage the api v1 routes requests.
  • controller.api.v2: exposes the v2 business logic needed to manage the api v2 routes requests.
  • controller.bus: handles the asynchronous api bit of the workflow exposing the business logic needed to manage the requests coming as rabbitmq bus messages.
• bus: manages the connection with the rabbitmq bus exposing publishing and subscribing functionalities.
• store: manages the connection with the mongodb database exposing storing and retrieving functionalities.

app

The root component defining the service system.

logger

The logging component providing the following logs structure:

{TIMESTAMP} | {LOG_LEVEL} [{service-systemic-showcase}] | {MESSAGE}

express

An express server that always comes in handy to expose at least a set of admin endpoints for monitoring purposes.

config

The component in charge of mixing and set up the configuration defined into the files of the folder /config in order to come up with the correct configuration for the given run mode:

• default
• local
• test
• build
• prod

routes

The component in charge of specifiyng the routes to be exposed by the express component.

routes.admin

The admin api sub-component in charge of exposing the /__/manifest endpoint.

routes.api.v1

The api v1 sub-component in charge of exposing the /v1/message/{id} endpoint. It is capable of dealing with the defualt http errors thanks to the module error-handler-module (e.g. 404 NOT_FOUND_ERROR).

routes.api.v2

The api v2 sub-component in charge of exposing the /v2/message/{id} endpoint. It is capable of dealing with the defualt http errors thanks to the module error-handler-module (e.g. 404 NOT_FOUND_ERROR).

controller

Is the orchestrator of the different components and subcomponents of the system, handles the core logic of the Hexagon Architecture.

controller.api.v1

Implements the v1 business logic needed to manage the api v1 routes requests. It retrieves a given message from the store and manipulates its payload in order to give back to the api v1 request a response containing:

• id: original message id.
• text: lowercase original message text.

controller.api.v2

Implements the v2 business logic needed to manage the api v2 routes requests. It retrieves a given message from the store and manipulates its payload in order to give back to the api v2 request a response containing:

• id: original message id.
• text: uppercase original message text.
• receptionTimestamp: ISO string timestamp of the original message reception time.

controller.bus

Implements the business logic needed to manage the messages coming from the rabbitmq bus. It is in charge of storing the original payload messages along with the reception timestamp into the monogodb store.

store

Manages the connection with the mongodb database exposing storing and retrieving functionalities of messages which in turn will be exploited by the controllers.

CONFIG

The configuration is scattered across different files and mixed according to the service run mode as said above. The intesting bit is the fact that is stored in js objects and is definable per-component and per-sub-component.

E.g. routes and routes.admin default configuration:

{
    routes: {
		admin: {
			swaggerValidator: {
				apiDocEndpoint: '/__/docs/api',
				validateRequests: true,
				validateResponses: true,
				validationEndpoint: '/test',
				format: 'yaml',
				yaml: {
					file: './docs/syncapi.yaml',
				},
			},
		},
    },
}

Note that the configuration varies according to the different run modes. Particularly the rabbitmq one for the systemic-rabbitmq component coming as an npm library:

• Default: according the the business logic of our service the default config is needed only for the service to be subscribed to a given queue.
• Test: in order to test the service business logic during the test phase is the very same service the one publishing the messages that is going to consume. More info in the test section.

DOCS

The /docs folder holds the synchronous api documentation for the endpoints exposed by the routes component. As defined in the above section the syncapi.yaml is used by the swagger-endpoint-validator in order to:

• validate the requests and responses.
• expose the swagger api documentation at the /__/docs/api endpoint.

DOCKER

• Dokcerfile: the service is dockerized and ready to be shipped thanks to the Dockerfile.
• docker-compose.yml: the service comes with a docker compose file in order to manage the infrastructure needed by the service to be up and running (i.e. rabbitmq - mongodb)

MAKE

The service comes whit an easy and lean makefile that can be used as a base for any CI/CD tool that need to manage the service.

START

Starting the service means to start the system components and sub-components in the proper order. Something that the index.js and the system.js files are taking care of. In order for the service to be up and running the related infrstructure must be in place.

npm run infra-up
npm run sleep // waits for the rabbitmq docker image to be running
npm run start

TEST

The service comes with a simple tests framework already in place in the /test folder.

There is one test in charge of checking the whole integration chain that is almost and end to end test and does the following:

1. publishes a message into the very same rabbitmq queue that the service itself is subscribed to.
2. waits for the message to be received by the service and stored into the mongodb database.
3. calls the /v1/message/{id} endpoint and checks the correctness of the response.
4. calls the /v2/message/{id} endpoint and checks the correctness of the response.

getting the infrastructure up with docker-compose

npm run infra-up

Note: even if the rabbitmq docker container is up please check that the admin interface is running since it can take up to 30 seconds to be ready.

running the tests

npm run test

putting the infrastructure down with docker-compose

npm run infra-down

note about a nasty hack

The rabbitmq docker container can be up thanks to docker compose but is not actually running until 20 seconds after it started, that is where the npm sleep script comes in handy.