This repository is the source code for NGINX, a production-grade web server, reverse proxy, load balancer, API gateway, and mail proxy. The codebase is written entirely in C and is a definitive example of high-performance systems architecture. It employs a modular, event-driven, multi-process (master/worker) model. The core infrastructure is built around a set of highly optimized, self-contained data structures and utilities: a slab allocator for shared memory, a memory pool for request-scoped allocation, a red-black tree for timers and caches, a radix tree for IP routing, a hash table with wildcard support for server name matching, and an incremental JSON parser. The build system (auto/) is a sophisticated set of shell scripts that handle platform detection, dependency configuration, and module compilation. The code supports HTTP/1.x, HTTP/2, HTTP/3 (QUIC), TCP/UDP proxying (Stream module), and mail protocols (POP3, IMAP, SMTP). It is actively maintained, with a strong focus on performance, stability, and security. The code is exceptionally clean and well-structured for a project of its age and complexity, though it contains some platform-specific #ifdef sprawl and duplication between HTTP and Stream modules (e.g., upstream least_time, map).
MetalLB is a Kubernetes-native load balancer for bare-metal clusters. Two cooperating workloads implement the system: a cluster-scoped controller that allocates IP addresses from CRD-defined IPAddressPools and writes Service status updates, and a DaemonSet of speaker pods on each node that announce assigned IPs to the physical network. Announcement is either BGP (via a from-scratch native Go BGP stack, a deprecated FRR sidecar mode, or the newer FRR-K8s API that generates FRRConfiguration CRs) or Layer2 (ARP/NDP responders with memberlist-based fast failover detection and deterministic speaker election). All user configuration flows through CRDs — IPAddressPool, BGPPeer, BGPAdvertisement, L2Advertisement, Community, BFDProfile, and ConfigurationState — validated by admission webhooks, with a configmaptocrs tool migrating legacy ConfigMap configuration to the CRD model. The controller/speaker split, a listener abstraction that delivers config changes to protocol handlers, and a common bgp.Session interface across backends give the architecture a clean, modular shape.
Traefik is a cloud-native reverse proxy and API gateway that dynamically configures itself from various service discovery backends (Docker, Kubernetes, Consul, etc.). It provides HTTP, TCP, and UDP routing, load balancing, TLS termination, ACME certificate management, a rich middleware chain (auth, rate limiting, compression, headers, etc.), observability (metrics, tracing, access logs), and a plugin system (Yaegi and Wasm). The project is written in Go with a React-based web UI. It supports Kubernetes CRDs (IngressRoute, Middleware, etc.) and the Gateway API. It has extensive integration tests and is actively maintained. The architecture is modular with clear provider interfaces, a configuration watcher that merges dynamic configs from multiple sources, and a hot-swappable handler for live updates.
One API is a production-ready OpenAI API gateway that aggregates 30+ LLM providers (OpenAI, Anthropic, Google Gemini, Azure, Baidu, Alibaba, Zhipu, Moonshot, DeepSeek, Ollama, etc.) behind a single OpenAI-compatible endpoint. The Go backend implements a sophisticated relay system with provider-specific adaptors that translate OpenAI-format requests to each provider's native API. It features token-based quota management with group/channel multipliers, load balancing across channels, automatic failover, channel health monitoring with metric-based auto-disable, and multi-node deployment with Redis synchronization. The React frontend (three themes: default, berry, air) provides admin dashboards for channel/token/user management, billing visualization, and system configuration. The codebase demonstrates strong engineering practices: clean adaptor pattern for provider extensibility, comprehensive middleware chain, batched database updates for performance, and well-structured configuration management.
PM2 is a production process manager for Node.js applications with built-in load balancing, monitoring, and deployment capabilities. It keeps applications alive forever, enables zero-downtime reloads, and provides comprehensive system administration features. The architecture features a daemon-based design with CLI and programmatic APIs communicating via IPC (pm2-axon). Key capabilities include process clustering, log management, metrics collection, Docker integration, startup script generation, and a plugin system for extensibility. The codebase demonstrates strong engineering practices with internalized dependencies to reduce supply chain risk, comprehensive test coverage, and active maintenance with regular updates supporting Node.js >=18 and Bun.
NyaProxy is a lightweight API gateway/proxy service built with FastAPI and Uvicorn that manages authentication, credential rotation, load balancing, rate limiting, and observability for HTTP APIs. It acts as an intermediary between clients and upstream services, injecting credentials, enforcing quotas, and providing features like retry logic, key quarantine, and request/response transformation. The system includes a web dashboard for monitoring traffic, metrics, and queue status, and exposes Prometheus metrics for external monitoring. The architecture follows a modular design with separate concerns: core proxy logic (queue-first request handling), traffic management (load balancing and rate limiting), configuration management (using Nacho for layered config and schema validation), services (metrics, state persistence), and a dashboard interface. Requests are processed via a priority queue with worker pools, enabling prioritization of retries and high-priority requests. State persistence saves rate limit windows and key cooldowns to disk using SHA256-hashed keys to avoid storing secrets, allowing survival across restarts. Key entry points include the CLI (`python -m nya` or `nyaproxy` script) and the main application factory in `nya/server/app.py`. The system relies on dependencies like FastAPI, Uvicorn, Pydantic, Nacho, and the Prometheus client, with explicit version pins in `pyproject.toml` and regular updates shown in the changelog. The codebase demonstrates strong engineering practices including comprehensive test coverage (unit and end-to-end), secure secret handling, and clean separation of concerns.
KaHIP (Karlsruhe High Quality Partitioning) is a high-performance C++ library and command-line toolkit for graph partitioning, node ordering, and mapping. It implements multilevel partitioning with advanced refinement techniques including Fiduccia-Mattheyses local search, flow-based min-cut refinement, cycle improvements, and tabu search. The library provides a C API for integration into external applications, along with Python bindings and a Java JNI wrapper. The codebase includes both a sequential version and a distributed-memory parallel version (ParHIP) using MPI, enabling partitioning of large graphs on clusters. Core algorithms are well-structured with modular coarsening, initial partitioning, and uncoarsening/refinement phases, supporting multiple matching strategies (GPA, random, label propagation) and quality/speed trade-offs via preconfigured modes (Strong, Eco, Fast, Social). Despite research-grade complexity and some code duplication between serial and parallel variants, the library is actively maintained and widely used in scientific computing and graph analytics.