production-evyos-systems-and-services-3/ServicesBank/RoutineEmail/README.md

Routine Email Service

Overview

This service sends automated email reports about account records at scheduled times using cron. It retrieves account records from a PostgreSQL database, formats them into an HTML email, and sends them to specified recipients.

Environment Setup

The service requires the following environment variables:

Email Configuration

• EMAIL_HOST: SMTP server address (e.g., "10.10.2.34")
• EMAIL_USERNAME: Email sender address (e.g., "example@domain.com")
• EMAIL_PASSWORD: Email password (sensitive)
• EMAIL_PORT: SMTP port (e.g., 587)
• EMAIL_SEND: Flag to enable/disable email sending (1 = enabled)

Database Configuration

• DB_HOST: PostgreSQL server address (e.g., "10.10.2.14")
• DB_USER: Database username (e.g., "postgres")
• DB_PASSWORD: Database password (sensitive)
• DB_PORT: Database port (e.g., 5432)
• DB_NAME: Database name (e.g., "postgres")

Cron Job Configuration

The service is configured to run daily at 11:00 Istanbul Time (08:00 UTC). This is set up in the entrypoint.sh script.

Docker Container Setup

Key Files

1. Dockerfile: Defines the container image with Python and cron

2. entrypoint.sh: Container entrypoint script that:

   • Creates an environment file (/env.sh) with all configuration variables
   • Sets up the crontab to run run_app.sh at the scheduled time
   • Starts the cron service
   • Tails the log file for monitoring

3. run_app.sh: Script executed by cron that:

   • Sources the environment file to get all configuration
   • Exports variables to make them available to the Python script
   • Runs the Python application
   • Logs environment and execution results

Environment Variable Handling

Cron jobs run with a minimal environment that doesn't automatically include Docker container environment variables. Our solution:

1. Captures all environment variables from Docker to a file at container startup
2. Has the run_app.sh script source this file before execution
3. Explicitly exports all variables to ensure they're available to the Python script

Logs

Logs are written to /var/log/cron.log and can be viewed with:

docker exec routine_email_service tail -f /var/log/cron.log

Manual Execution

To run the service manually:

docker exec routine_email_service /run_app.sh

Docker Compose Configuration

In the docker-compose.yml file, the service needs an explicit entrypoint configuration:

entrypoint: ["/entrypoint.sh"]

This ensures the entrypoint script runs when the container starts.