Exploring Plumber: Semaphore's Pipeline Management and Architecture

The article delves into Plumber, the orchestration engine used by Semaphore to manage CI/CD pipelines. It explains how Plumber interprets YAML pipeline definitions, schedules jobs, and coordinates execution among distributed agents, ensuring reliability and scalability. The authors detail how the pipeline operates from the moment code is pushed to a Git repository to the execution of jobs, and the importance of a finite state machine (FSM) model in managing pipeline states. They also cover the technical stack behind Plumber, including technologies like Elixir, PostgreSQL, RabbitMQ, and Kubernetes, which allow for fault tolerance and horizontal scaling. Furthermore, it discusses mechanisms for handling failures and extending pipeline behavior, emphasizing reliability and extensibility as core principles. The article ultimately showcases how Plumber is designed to meet the growing demands of continuous integration and deployment for developers.