# MengRao/fmtlog

fmtlog is a performant fmtlib-style logging library with latency in nanoseconds.

Repository: https://github.com/MengRao/fmtlog
Canonical: https://ross.abutalabs.com/products/fmtlog
Language: C++
License: MIT
License Family: permissive
Topics: high-performance, logging-library, logging, fmtlib, low-latency
Last push: 2025-02-13T08:08:39+00:00

## Health v2 (maintenance only)
Score: 26/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 6, release rhythm 8, longevity 100
- inputs: {"age_days": 1950, "days_push": 566, "days_rel": 566, "gap_med": null, "n_releases_24m": 1}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1025, forks 157 (observed 2026-08-28T04:03:16.646839+00:00)

## What it is
fmtlog is a high-performance C++ logging library built on the fmt library, offering nanosecond-level runtime latency and asynchronous multi-threaded logging in time order. It can be used header-only or compiled as a static/shared library, with runtime and compile-time log level filtering.

## Use cases
- log with nanosecond-level latency in a low-latency C++ trading system
- replace spdlog with a faster fmtlib-style logger
- do asynchronous multi-threaded logging that preserves time order
- filter and change log levels at runtime
- rate-limit noisy log statements
- handle log messages with a custom callback

## When to choose
- you need extremely low logging latency in C++
- you want fmt-style formatting with high throughput
- you want full control over polling and flushing threads

## When to avoid
- you need a batteries-included logger with built-in sinks and rotating files like spdlog
- you need platforms beyond Linux and Windows
- you don't want to manage a background polling thread or call poll() yourself

## Facets
- artifact type: library
- maturity: active
- function: logging, serialization
- domain: developer-tools, performance, backend
- platform: windows, cpp, cross-platform
- tags: fmtlib, low-latency, asynchronous-logging, header-only, nanosecond-latency, linux

## Member repositories
- MengRao/fmtlog (main) score 26

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:16.646839+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T07:08:01.847526+00:00, confidence not recorded.
  - readme: https://github.com/MengRao/fmtlog (fetched 2026-08-28T04:03:16.646839+00:00, sha 4423908eb8c7)
- Data as of 2026-08-30T08:39:29.467469+00:00.