$ show valyala/fasthttp
Fasthttp is a high-performance HTTP/1.1 server and client library for Go, designed as a drop-in replacement for the standard `net/http` package with significantly lower latency and memory allocations. It achieves this through extensive use of `sync.Pool` for object reuse, zero-allocation byte-to-string conversions (`b2s`/`s2b`), stackless goroutine wrappers for compression, and a custom worker pool that keeps CPU caches hot. The library handles both server and client roles, supporting TLS, keep-alive, pipelining, load balancing (via `LBClient`), transparent retries, and streaming request/response bodies. It also provides a rich set of sub-packages for proxy dialing (`fasthttpproxy`), `net/http` adapter (`fasthttpadaptor`), listener reuse (`reuseport`, `tcplisten`), in-memory testing utilities (`fasthttputil`), and prefork process management for multi-core deployments. The architecture is modular: core types (`Server`, `Client`, `HostClient`, `RequestCtx`, `Request`, `Response`, `Headers`, `URI`, `Cookie`, `Args`) are in the root package, while optional features live in sub-packages. The server uses an event-driven, non-blocking I/O model with a worker pool that reuses goroutines and allocates few objects per request. The client maintains connection pools with idle timeout and supports both FIFO and LIFO connection reuse to minimize latency. Extensive test coverage, including fuzz tests and allocation benchmarks, validates correctness and performance across edge cases and shared-nothing concurrency. Fasthttp is production-hardened, powering services like VertaMedia at over 200K requests per second per server with 1.5M concurrent keep-alive connections. It is not a generic web framework but a foundational layer that can be embedded into frameworks (including gin, echo, etc.) via adapters. The codebase demonstrates advanced Go patterns for high-performance I/O, making it a reference for engineers building latency-sensitive network services.
The LLM identified 6 files worth highlighting for reuse:
Implements a FILO worker pool for processing incoming connections, reducing CPU cache misses by reusing the most recently used goroutine. The pool grows and shrinks based on demand and provides graceful shutdown. This pattern is reusable in any Go server where connection handling is the bottleneck.
Provides a load-balancing HTTP client that distributes requests across multiple HostClients using a hybrid least-loaded + least-total strategy. Includes health checks, penalty smoothing for failed endpoints, and automatic failover. Can be extracted and reused as a generic load-balancing wrapper for any RoundTripper.
Implements stackless goroutine execution for CPU-bound or helper functions (e.g., compression) to avoid allocating large goroutine stacks. Functions are wrapped to run in a small pool of goroutines, reducing memory pressure under high concurrency. This pattern is reusable for optimizing goroutine-heavy systems.
Provides dialer implementations for HTTP CONNECT proxy and SOCKS5 proxy. Includes support for proxy environment variables (HTTP_PROXY, HTTPS_PROXY, NO_PROXY) and automatic fallback. The dialer interface is decoupled from fasthttp and can be reused with any net.Conn-based client.
Provides a configurable TCP listener with platform-specific optimizations: SO_REUSEPORT for socket sharding, TCP_DEFER_ACCEPT to reduce accept overhead, TCP_FASTOPEN for 0-RTT connections, and SO_RCVBUF/SO_SNDBUF tuning. The listener can be used with any net.Listener consumer; demonstrates how to apply kernel-level tuning in Go.
Implements an in-memory TCP listener that creates virtual connections via net.Pipe, enabling zero-network testing of HTTP servers and clients. Useful for integration tests without port allocation. The listener is thread-safe and can be paired with fasthttp's server for deterministic test setups.