single-worker

README

Single Worker Example

This example demonstrates the simplest possible projection setup: one projection running on a single worker with no partitioning.

What It Does

• Runs a single projection that counts user creation events
• Processes events sequentially from the event store
• Gracefully handles shutdown signals (Ctrl+C)
• Automatically resumes from the last checkpoint on restart

Running the Example

1. Start PostgreSQL:

docker run -d -p 5432:5432 -e POSTGRES_PASSWORD=postgres -e POSTGRES_DB=pupsourcing_example postgres:16

1. Run migrations (from the basic example directory):

cd ../basic
go generate
# Apply the generated migration to your database

1. Run the example:

go run main.go

Key Concepts

• Checkpoint Tracking: The projection automatically tracks its position in the event stream
• Resumability: Stop and restart the process - it picks up where it left off
• Simplicity: This is the baseline pattern - perfect for getting started

When to Use This Pattern

• Small to medium event volumes (< 1000 events/sec)
• Simple projections that can keep up with event production
• Development and testing environments
• Applications where projection lag is not critical

Scaling Up

When this pattern is not sufficient, see:

• ../partitioned - Scale with partitioning in separate processes
• ../worker-pool - Scale with partitions in the same process

Documentation

Overview

Package main demonstrates a single projection running on a single worker. This is the simplest possible setup - one projection, one process, no partitioning.

Run this example:

1. Start PostgreSQL: docker run -d -p 5432:5432 -e POSTGRES_PASSWORD=postgres -e POSTGRES_DB=pupsourcing_example postgres:16
2. Run migrations from the basic example
3. Run this example: go run main.go