The Actor pattern is a design pattern for concurrent computation where independent “actors” communicate exclusively through message passing rather than shared memory.
In Ruby Concurrency Mechanisms, Ractors implement this pattern to achieve true Parallelism. Each Ractor operates as an isolated actor with its own Global Interpreter Lock, enabling multiple Ractors to execute Ruby code simultaneously across CPU cores.
Key Characteristics
The Actor pattern in Ractors enforces Thread Safety through isolation:
- Ractors have limited ability to access variables outside their scope
- Communication between Ractors occurs through specific, pre-defined message-passing mechanisms
- This architectural constraint prevents race conditions by making shared mutable state impossible
The pattern was initially developed under the name “Guilds” during its experimental phase before being released as Ractors in Ruby 3.0.
By design, actors avoid the complexity of locks and mutexes by simply prohibiting direct access to shared memory—a radically different approach from traditional threaded programming.