MockServer is a highly sophisticated, multi-protocol HTTP(S) mock server and proxy for testing, written in Java with Netty. It supports HTTP/1.1, HTTP/2, HTTP/3 (QUIC), gRPC, WebSockets, DNS, TCP, and binary protocols on a single port. The core engine provides expectation-based request matching, response generation, forwarding, proxying, recording, verification, and chaos engineering (latency, connection drops, error injection). It also includes built-in LLM mocking (OpenAI, Anthropic, Gemini, etc.), OIDC/OAuth2/SAML identity providers, SCIM provisioning, WASM custom rules, and drift detection. The repository is a monorepo containing the Java server, multi-language client libraries (Java, Node, Python, Ruby, Go, .NET, Rust, PHP), a React dashboard UI, IDE plugins (JetBrains, VS Code), Helm charts, Docker images, and extensive CI/CD pipelines via Buildkite. The architecture is modular with clear separation of concerns: core model/matcher/serialization in `mockserver-core`, Netty transport in `mockserver-netty`, language-specific clients in `mockserver-client-*`, and a React UI in `mockserver-ui`. The codebase demonstrates strong engineering practices including DTO patterns with Jackson serializers, a matcher hierarchy with compiled-once validators, bounded caches, constant-time equality checks, and extensive test coverage with integration tests across multiple environments.
This is the official Sentry JavaScript SDK monorepo, providing error monitoring, performance tracing, session replay, user feedback, and profiling for a wide range of JavaScript runtimes and frameworks. The architecture is a large monorepo with ~50 packages, each targeting specific platforms (browser, Node.js, Cloudflare Workers, Deno, Bun) and frameworks (Next.js, Angular, React, SvelteKit, Nuxt, etc.). The core SDK logic lives in `packages/core`, with platform-specific packages that integrate via a consistent `Sentry.init()` entry point. Data flows from the user's application through instrumented APIs (error handlers, fetch, timers, etc.) to produce events (errors, spans, breadcrumbs, replay recordings) that are serialized into envelopes and sent to Sentry's ingest endpoint via configurable transports. The monorepo also includes bundler plugins for build-time instrumentation (source map upload, debug ID injection, component annotation) and extensive integration tests covering multiple bundler versions and framework releases. The codebase exhibits high craftsmanship with well-defined integration patterns (`defineIntegration`), modular utilities, and comprehensive test infrastructure. It is actively maintained with frequent commits and a broad compatibility surface, though the sheer number of framework-specific packages introduces some maintenance complexity.
This repository is the official JavaScript/TypeScript client SDK for Centrifugo, a scalable real-time messaging server. It provides a robust, event-driven client (Centrifuge class) that manages persistent connections via multiple transports (WebSocket, SSE, HTTP stream, SockJS, WebTransport), handles token-based authentication and subscription authorization, and supports three subscription models: stream (standard channel), map (keyed data), and shared poll (polling with version tracking). The SDK also implements advanced features like automatic reconnection with exponential backoff, recovery from connection drops using offset/epoch, command batching for HTTP transports, and delta compression for efficient updates. The architecture is library-oriented with a clear separation of concerns: transport implementations are abstracted behind a common interface, the main client class manages connection state and dispatch ordering via a serial promise chain, and each subscription type extends a base class with its own state machine (stream, map three-phase, shared poll). The codebase is extensively tested with both unit tests (using a fake server) and integration tests against a real Centrifugo instance in Docker. The SDK is published on npm, supports CJS and ESM builds, and includes protobuf codec support. Notable patterns include a transport abstraction with dependency injection that allows easy addition of new transports, a serial dispatch chain ensuring ordered response processing, and a per-key publish debounce mechanism. The library is actively maintained with ongoing work on refactoring subscription types as documented in NEXT_MAJOR_SUBSCRIPTION_TYPES.md. The repository also demonstrates high craftsmanship in its comprehensive test coverage, graceful error handling, and careful handling of edge cases like stale tokens, network interruptions, and concurrent operations.