Workflow Coordination with RabbitMQ and PostgreSQL

This project demonstrates the Request-Reply pattern using RabbitMQ for message coordination between a workflow coordinator and worker processes, with PostgreSQL for state management.

Test database commands

1. Start PostgreSQL Docker Container

docker run --name postgres -e POSTGRES_PASSWORD=mysecretpassword -p 5432:5432 -d postgres

2. Create Database

docker exec -it postgres psql -U postgres -c "CREATE DATABASE workflowdb;"

3. Create Table and Insert Test Data

docker exec -it postgres psql -U postgres -d workflowdb -c "
  CREATE TABLE work_items (
    id SERIAL PRIMARY KEY,
    status VARCHAR(50) NOT NULL DEFAULT 'Pending',
    data TEXT,
    started_at TIMESTAMP,
    completed_at TIMESTAMP,
    result TEXT
  );
  
  INSERT INTO work_items (status, data) VALUES 
    ('Pending', 'Process customer order #1001'),
    ('Pending', 'Generate monthly report'),
    ('Pending', 'Send notification emails');
"

4. Verify Test Data (Optional)

docker exec -it postgres psql -U postgres -d workflowdb -c "SELECT * FROM work_items;"

Useful Database Commands

Reset All Work Items to Pending

docker exec -it postgres psql -U postgres -d workflowdb -c "UPDATE work_items SET status = 'Pending', started_at = NULL, completed_at = NULL, result = NULL;"

Reset Specific Work Item to Pending

docker exec -it postgres psql -U postgres -d workflowdb -c "UPDATE work_items SET status = 'Pending', started_at = NULL, completed_at = NULL, result = NULL WHERE id = 1;"

View All Work Items

docker exec -it postgres psql -U postgres -d workflowdb -c "SELECT * FROM work_items;"

View Only Pending Work Items

docker exec -it postgres psql -U postgres -d workflowdb -c "SELECT * FROM work_items WHERE status = 'Pending';"

Troubleshooting (Errors that quite easily can be encountered again)

"Work item not available" Error

The work item is not in 'Pending' status. Reset it using the database commands above.