Quill is an ultra-low-latency asynchronous C++17 logging and metrics library designed for performance-critical applications.
The library addresses the need to minimize logging overhead in latency-sensitive systems by using asynchronous logging where log messages are queued and written by a background thread, keeping the critical path unblocked. It provides structured logging capabilities and integrates with Prometheus for metrics collection, enabling observability without sacrificing application performance.
Quill suits projects where microsecond-level latency matters: high-frequency trading systems, real-time data processing, and other performance-critical applications where traditional synchronous logging would introduce unacceptable delays. The library supports C++17 and C++20, runs cross-platform on Linux, macOS, Windows, and BSD, and uses fmtlib for efficient string formatting. Teams choosing this tool should expect to integrate a header-only or compiled library into their build system and accept the design constraint that logging happens asynchronously, which requires careful shutdown handling to ensure all messages are flushed.
The project maintains continuous integration across multiple platforms and compilers including Fedora, Ubuntu, BSD, macOS, Windows, and Intel LLVM, with automated fuzz testing to catch edge cases. Code quality is monitored through coverage tracking and static analysis tools. The codebase demonstrates attention to reliability through comprehensive testing infrastructure.
