Email delivery service

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Basic overview

This project consists of 6 services (containers) described in a docker-compose.yml descriptor file that works together to send email messages, in a way that it is possible to scale the services as needed.

Individual images:

• db container(Postgres) - Postgres database server for storing email messages sent by the application in the app contianer.

• adminer container(Adminer) - Database management service, used in the project only to monitor the databased stored in the db service. It's an optional service and it's just for monitoring the inserted data from emails table.

• frontend container(Nginx) - A web service that exposes in the door 80 a web form that allows user fill out an email message, and it also acts like a reverse proxy, routing the posted form message to the http://localhost/api route, which is the service described in the app container.

• app container(Python) - It's the service that recieves a message via POST from frontend container, inserts the message at the db container database created earlier, and then send this message to the queue from queue container

• queue container(Redis) - Recieves the messages created by app container, then this messages are available to be retrieved by the worker container, which will trigger the emails later.

• worker container(Worker) - A custom Python image with Redis, to read and recieve messages from queue container, and then send the email message throught a smtp server. This is the container that could be scaled as soon as needed, using the flag --scale as described in the next section "Up and running".

Up and running

1. First of all, clone the repo: git clone [email protected]:dhfuzari/email-delivery-service.git

2. Next, open the root folder: cd email-delivery-service

3. Then, before to start, you must to create a mailtrap account and replace the current environment xpto variables values from SMTP_USER and SMTP_PASSWORD at docker-compose.override.yml file, with the new values created at mailtrap. xpto isn't a valid mailtrap user and isn't even a valid mailtrap password. Now, you're almost ready to go.

4. To execute the services in daemon mode, with only one worker container instance, run the command:

   docker-compose up -d
   

   If you want to scalate the number of worker containers, then use the --scale flag and assign the number of containers you wish to the containers name. In the example, we'll have 3 worker containers working in parallel:

   docker-compose up -d --scale worker=3
   

5. Navigate to http://localhost:80

6. Fill the form with requested data and click on send

7. The adminer service used to track email data stored in Postgres is available via the URL http://localhost:81. To authenticate in it, use the followind credentials:

   System: Postgres
   Server: localhost
   User: postgres
   Password: p@ssw0rd

Useful commands:

To view logs for all running containers:

docker-compose logs -f -t

List all available databases from db container

docker-compose exec db psql -U postgres -c '\l'

Run the check.sql script tha list all databases, set the current conexion to email-sender database, and displays a complete emails talbes description

docker-compose exec db psql -U postgres -f /scripts/check.sql

Stop containers services defined in the compose file

docker-compose down

Performs a SELECT for all records at email's table in the email-sender database, at db container

docker-compose logs exec db psql -U postgres -d email_sender -c 'SELECT * FROM emails'

Displays logs information about a specific container. In the example displays logs from worker container

docker-compose logs -f -t worker

Configuration

Important note for windows users: The default setup to run the web service in the frontend container is the door 80, therefore for Microsoft Windows system with IIS up and running at door 80, it'll be necessary to stop it's execution, to release the door 80 to our Nginx container. To achieve this, open powershell as admin, and run the following command:

iisreset /stop

Important note if you need to change database structure: The initialization Postgres file /docker-entrypoint-initdb.d/init.sql is executed only when the path /var/lib/postgresql/data from instance is completely empty. Keep in mind that if you need to update the initialization script created earlier, it'll not execute again with the new update, because the path /var/lib/postgresql/data is no longer empty after the first db container execution, and after the init.sql file execution. It's necessary execute the following comand to remove containers and delete the volume created earlier:

docker-compose down -v

The volumes and networks are described in docker-compose.yml file, each one in it's own service details.

If necessary override some values, update then in docker-compose.override.yml

Environment variables:

• DB_HOST=db
• DB_USER=postgres
• DB_PASSWORD=p@ssw0rd
• DB_NAME=email_sender
• REDIS_HOST=queue
• SMTP_USER=xpto
• SMTP_PASSWORD=xpto

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

License

MIT