James Harton

Ash Core Team Member and Perennial Non-finisher of Projects

James Harton is a Principal Consultant at Alembic and Ash core team member. He is the author of Reactor, Ash Authentication and many other libraries in the Elixir ecosystem. Based in New Zealand, James has been building production systems with Elixir since 2015 and brings a pragmatic approach to solving complex distributed systems problems. When he’s not writing libraries that make other developers’ lives easier, you’ll find him contributing to open source projects, mentoring developers, or exploring ways to make Elixir more accessible to newcomers. His work focuses on building tools that hide complexity without sacrificing power - because the best abstractions are the ones you don’t have to think about.

Talk:
Reactor Under the Hood: Building a Graph-Based Saga Orchestrator in Elixir

Here’s the thing - workflow engines sound complicated, but they don’t have to be. I’ll show you how Reactor uses a dead simple graph algorithm (find nodes with no dependencies, run them, remove them, repeat) to build something genuinely useful. We’ll dig into how this basic approach, combined with OTP, gives you concurrent execution with concurrency limits, automatic retries, compensation when things go wrong (and they will), and the ability to compose workflows inside each other. You’ll see how we made the simple cases easy without making the complex cases impossible.

Key Takeaways:

  • How a basic graph traversal becomes a proper execution engine when you add OTP to the mix
  • Managing shared concurrency pools so nested Reactors don’t starve each other of resources
  • Building compensation patterns that actually work when production decides to test your error handling
  • Making APIs that don’t make developers want to flip tables (harder than it sounds)

Target Audience:

  • Elixir developers who want to understand advanced OTP patterns, folks building libraries, system architects