How do I migrate events when my domain model changes in Rails Event Store?

RES supports event upcasting and transformations through contributed gems like ruby_event_store-transformations. You can version events and apply migrations during replay, but it requires careful planning to avoid data loss and ensure backward compatibility.

Rails Event Store or Kafka for event-driven architecture?

RES is ideal for within-application event handling, audit trails, and event sourcing in Rails, while Kafka excels at cross-service streaming and high-volume data pipelines. Use RES for domain events inside your app and Kafka for system-wide integration.

How to set up asynchronous event handlers with Sidekiq?

RES integrates with Sidekiq via the ruby_event_store-sidekiq_scheduler gem. Configure handlers to run in background jobs by subscribing with asynchronous options, ensuring non-blocking event processing and better scalability for side-effects.

Can Rails Event Store work with JSONB columns in PostgreSQL?

Yes, since RES uses ActiveRecord, you can store event data in JSONB columns for flexibility. The default schema allows customizing storage, but you may need to adjust migrations to leverage JSONB features effectively.

What's the performance impact of using Rails Event Store on high-traffic apps?

Event storage adds write overhead, but RES is optimized for Rails and can scale with database tuning. For read-heavy scenarios, use read-models to cache projections and avoid querying the event log directly, which can mitigate performance hits.

How does event sourcing with RES handle concurrency issues?

RES provides optimistic concurrency control through event versioning and aggregate roots. When saving aggregates, it checks for conflicts using version numbers to prevent lost updates, ensuring consistency in concurrent environments without locking.

Open-Awesome

aggregate_root

MITRubyv2.18.0

A Ruby library for implementing event-driven architectures in Rails applications, providing event publishing, storage, and subscription.

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1.5k stars128 forks0 contributors

What is aggregate_root?

Rails Event Store is a Ruby library that implements an event store for Rails applications, enabling developers to publish, store, and subscribe to events. It solves the problem of tightly coupled architectures by providing a robust foundation for event-driven design, audit logging, and event sourcing. It acts as a central hub for domain events, replacing patterns like ActiveRecord callbacks with more explicit and scalable event handling.

Target Audience

Rails developers and teams building complex applications who want to adopt event-driven architectures, implement event sourcing, or improve system decoupling and observability. It's particularly valuable for projects needing audit trails, domain event capture, or hexagonal architecture patterns.

Value Proposition

Developers choose Rails Event Store for its deep Rails integration, comprehensive feature set for event management, and strong emphasis on testing and reliability. It offers a battle-tested, open-source alternative to building custom event systems, with extensive documentation and a modular gem ecosystem that extends its capabilities.

Overview

A Ruby implementation of an Event Store based on Active Record

Use Cases

Best For

Implementing event-driven architectures in Rails applications
Building audit logs and compliance trails for domain actions
Decoupling business logic from side-effects like notifications or metrics
Creating read-models and projections for complex query needs
Replacing ActiveRecord callbacks with explicit domain events
Adopting event sourcing patterns for domain model persistence

Not Ideal For

Microservices architectures using multiple programming languages or non-Rails frameworks
Applications requiring high-throughput, real-time event streaming like financial trading platforms
Simple CRUD applications where traditional ActiveRecord patterns suffice without audit or decoupling needs

Pros & Cons

Pros

Seamless Rails Integration

Designed specifically for Rails, it hooks into ActiveRecord for persistence and follows Rails conventions, reducing setup friction as highlighted in the documentation.

Comprehensive Event Handling

Supports publish-subscribe with synchronous and asynchronous handlers, enabling decoupled architecture and side-effect extraction from controllers, as described in use cases.

Robust Testing Culture

The project enforces 100% mutation testing coverage across gems, ensuring high reliability and encouraging best practices in event-driven code.

Extensible Gem Ecosystem

Modular gems like ruby_event_store-browser for UI and ruby_event_store-rspec for testing provide tailored extensions without bloating the core, as shown in the gem list.

Cons

Active Record Lock-in

Event storage is tightly coupled to ActiveRecord, making it less suitable for apps using alternative ORMs like ROM or NoSQL databases without extra work from contributed gems.

Architectural Overhead

Implementing full event-sourcing requires significant design changes and can introduce complexity that outweighs benefits for straightforward domains, despite the library's practicality.

Steep Learning Curve

Adopting event-driven patterns forces teams to move beyond familiar ActiveRecord callbacks, requiring upfront investment in new mental models for events and aggregates.

Frequently Asked Questions

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