Shopify/semian

Semian is a Ruby library that protects applications from cascading failures by implementing circuit breakers and resource management for external dependencies like databases, caches, and HTTP services. It provides adapters for Active Record (MySQL, PostgreSQL, Trilogy), Redis, Net::HTTP, and gRPC, allowing developers to configure fail-fast behaviors and dynamic error thresholds. The system supports both classic fixed-threshold and adaptive PID-controller-based circuit breaking, with comprehensive tooling for testing, benchmarking, and CI integration.

6 changes.

This period marks the initial release of the Semian library, introducing core circuit breaking and semaphore-based resource protection features for Ruby applications. The work included implementing adaptive circuit breakers with PID controllers, adding specific adapters for Active Record, Trilogy, and PostgreSQL, and establishing a comprehensive test suite to ensure thread safety and correct state transitions.

5 changes.

This period focused on establishing a robust continuous integration environment and comprehensive test infrastructure. Key efforts included creating a dedicated Dockerfile for consistent CI builds, automating test execution via shell scripts, and developing extensive helper modules and fixtures to support reliable testing of adapters, circuit breakers, and database interactions.

9 changes.

This period focused on expanding Semian's compatibility by adding support for Redis 5.0, Active Record Trilogy, and gRPC adapters, accompanied by comprehensive test suites for these integrations. The work also included creating detailed usage examples for various HTTP and database clients, alongside new benchmarking scripts and experimental tests to profile performance and compare adaptive versus classic circuit breaker behaviors.

Added a suite of examples in the \examples/net\_http\ directory demonstrating how to integrate Semian with Ruby's standard \Net::HTTP\ library. These examples cover minimal circuit breaker and bulkhead configurations, extended usage with state change subscriptions, concurrency patterns using threads and process forks, dynamic resource configuration, and combined circuit breaker with bulkhead scenarios.

_examples/net\http · high confidence

This change introduces a new adapter file (lib/semian/redis/v5.rb) to support the Redis 5.0 gem. It integrates Semian's circuit-breaking logic by prepending modules to the Redis client and error classes. A key behavioral addition is the ability to configure whether OutOfMemory (OOM) errors trigger circuit opening; by default, OOM errors open circuits for backward compatibility, but users can now set \open\_circuit\_on\_oom: false\ to allow reads/deletes to continue during OOM conditions, aiding recovery. The adapter also ensures ReadOnly errors do not mark circuits as open, facilitating faster reconnection to new primaries, and maps RedisClient errors to Semian-specific error classes.

lib/semian/redis · high confidence

Added two example scripts (00\_circuit\_minimal.rb and 03\_circuit\_open.rb) demonstrating how to configure and use the Semian circuit breaker with the Active Record Trilogy adapter. The minimal example shows basic setup, while the second example illustrates circuit breaker state transitions (closed, open, half-open) and error handling when connecting to healthy and unhealthy MySQL instances.

_examples/activerecord\_trilogy\adapter · high confidence

A new Dockerfile (semian-ci) has been added to provide a consistent development and CI environment. It is based on Ruby 3.4.3, installs necessary build dependencies (build-essential, libssl-dev, default-mysql-client), and sets up the application bundle for testing.

dockerfiles · high confidence

New Ruby scripts have been added to the benchmarks directory to measure the performance impact of the Semian library. The \flamegraph.rb\ script profiles CPU usage and generates flame graphs for HTTP requests, while \lru\_benchmarker.rb\ measures the throughput and memory consumption of resource registration. Additionally, \net\_http\_acquire\_benchmarker.rb\ benchmarks the latency and memory usage of HTTP acquisition, supporting both baseline comparisons and specific Semian versions via the SEMIAN\_VERSION environment variable.

scripts/benchmarks · high confidence

The examples directory now includes a new \dual\_circuit\_breaker\_demo.rb\ script that demonstrates how to configure and switch between legacy and adaptive circuit breakers at runtime using a selector callable, alongside a \colors.rb\ utility that adds ANSI color formatting methods to the String class for improved output readability in examples.

examples · high confidence

Introduces the Semian library, which allows applications to control access to external services (such as MySQL or Redis) using semaphores and circuit breakers. This prevents system-wide performance degradation when external dependencies are slow or unresponsive. The library provides a registration API to define resources with configurable ticket counts, timeouts, and error thresholds, automatically opening circuits to fail fast after repeated errors and transitioning to half-open states for recovery. It supports global configuration for LRU caching, permissions, and thread safety, and includes built-in instrumentation and logging capabilities.

lib · high confidence

Semian now includes dedicated adapters for the Active Record Trilogy and PostgreSQL adapters, extending circuit breaker protection to these database connections alongside the existing MySQL2 support. The Trilogy adapter specifically implements \with\_resource\_timeout\ to dynamically adjust read timeouts during half-open state testing, while the PostgreSQL adapter provides a no-op implementation as it lacks IO-level timeout configuration. Additionally, the library introduces an adaptive circuit breaker that uses a PID controller to dynamically adjust rejection rates based on error rates, offering a more responsive alternative to the traditional fixed-threshold circuit breaker.

lib/semian · high confidence

The experiments directory now includes an \ExperimentalResource\ adapter that wraps a \MockService\ to simulate distributed service failures, allowing for complex testing of circuit breaker behaviors. This setup supports running both classic and adaptive circuit breaker experiments, featuring configurable endpoints, statistical latency distributions (log-normal), and service-wide degradation scenarios such as sudden error spikes, gradual error increases, and sustained loads. The addition includes a comprehensive suite of experiment scripts comparing adaptive versus classic circuit breaker performance under these varied stress conditions.

experiments · high confidence

The Semian C extension has been restructured from a single monolithic file into distinct modules (resource, sysv\_semaphores, tickets, types) to improve maintainability and clarity. This change introduces explicit Ruby method bindings for resource management, including new methods to acquire/release semaphores without a block, destroy resources, reset registered worker counts, and query ticket/worker status. It also adds support for configurable semaphore permissions, quota-based ticket allocation, and better error handling for missing or corrupted semaphores, while ensuring thread safety through metadata locking and GVL release during blocking semaphore operations.

ext · high confidence

The project now enforces consistent code style and formatting through new \.editorconfig\ and \.rubocop.yml\ files (including Shopify and thread-safety plugins). The \Rakefile\ has been updated to support parallel test execution, explicit example running, and benchmarking, while the default task now runs both tests and RuboCop. Additionally, a \.dockerignore\ file has been added to optimize Docker builds by excluding unnecessary files.

(repo-wide) · high confidence

Add test configuration for service host connectivity; Added binary SQL fixture for theme template tests; Added comprehensive test suite for Semian core components; Added gRPC test fixtures for the Echo adapter; Added test helper modules for adapters, background threads, circuit breakers, and time mocking; Automated test execution script for CI and local development; Expanded test coverage for database, HTTP, and gRPC adapters.

Added gemfiles to support testing against Active Record's PostgreSQL and Trilogy adapters, as well as various Redis client configurations (Redis 4, Redis 5, and redis-client). These files define the specific gem dependencies required to run the adapter-specific test suites.

gemfiles · high confidence

The gem now requires Ruby 3.2 or later and adds development dependencies for Active Record 8.1, PostgreSQL (pg), and gRPC 1.76.0, enabling testing and usage with these modern versions. The dependency list also includes Trilogy 2.9, hiredis 0.6, and redis 5.4.1, while updating linting tools like Rubocop to 1.81.7 and Shopify style guide to 2.18.0. The gemspec metadata has been updated to reflect the Shopify GitHub organization and include standard metadata fields.

(dependencies) · high confidence

Written by watchdog.canine.dev from the codebase's own history, inside the signed delivery this page is composed from.

• First survey — no prior run to compare against. CAI 72.

• Code Health 95
• Architecture 99
• Maturity 72
• Readiness 73
• Security 66

• 300 commits — 284 feature/other, 16 fixes

• (root) — 113 commits
• (repo) — 92 commits
• lib/semian — 46 commits
• .github/workflows — 18 commits
• test/adapters — 8 commits
• lib/semian.rb — 5 commits
• ext/semian — 4 commits
• .github/dependabot.yml — 2 commits
• examples/net_http — 2 commits
• experiments/Gemfile — 1 commit
• experiments/results — 1 commit
• gemfiles/activerecord_postgresql_adapter.gemfile.lock — 1 commit
• gemfiles/activerecord_trilogy_adapter.gemfile — 1 commit
• scripts/benchmarks — 1 commit
• test/adapter_test.rb — 1 commit
• test/circuit_breaker_test.rb — 1 commit
• test/lru_hash_test.rb — 1 commit
• test/simple_integer_test.rb — 1 commit
• test/thread_safe_integer_test.rb — 1 commit

• fix: Enable thread safety rubocop and fix issues
• fix: Fix Semian resource allocator pairing
• fix: Fix compatibility with Redis 5.0.7+ (#513)
• fix: Fix docker compose tests (#662)
• fix: Fix linting errors
• fix: Fix linting issue
• fix: Fix regex in Mysql2 adapter
• fix: Fix valid_raw_connection check
• fix: Fix yamllint warnings
• fix: Fix: Trilogy ActiveRecord adapter to be compatible with latest Rails edge. (#520)
• fix: Merge pull request #1047 from serioushaircut/fix-adapter-reentrancy-guard-strand
• fix: Merge pull request #547 from Shopify/bostonaholic/fix-dynamic-example
• fix: Merge pull request #584 from Shopify/ian/fix-lint
• fix: README: fix blog post links
• fix: Refresh dependencies for all adapters and fix time helper (#941)
• fix: minor fixes to example
• change: AR does not send a semicolon after a SQL statement
• change: Accept QueryIntent from Active Record 8.2 in execute_intent
• change: Add adaptive circuit breaker (#760)
• change: Add an experimental resource that we could run complex experiments with (#781)
• …and 280 more

Written by watchdog.canine.dev from the codebase's own history, inside the signed delivery this page is composed from.

Shopify/semian was measured the same way every project in this corpus was: the same rubric, at a pinned commit, with the result published in full. Point a surveyor at a repository you know and see whether you agree with it.