FlashMQ is a multi-threaded fast lightweight MQTT broker. It’s written in C++, using mostly POSIX (Linux) APIs, as an event-driven multi-core state machine. This means it aims to scale linearly with the amount of cores in a system, and likewise incur load linear to the amount of clients/messages. Currently, it’s capable of reaching one million messages per second at 1.3 gbit/sec on a single four core server (and play full motion ASCII video at the same time 😉 ), and handle more than four million connections on one server.

FlashMQ is still in beta, but it’s approaching its stable release. It’s on a release cycle and aims to provide the named features as stable.

Design goals/aspects

  • Simple yet powerful (fast and scales well).
  • One thread per CPU/core, with clients living in one thread only.
  • Event and readiness-change driven.
  • Very few dependencies, for ease of deployment and code stability.
  • Stable code base. MQTT is simple enough that you don’t need esoteric features or libraries, so using C++ and few external dependencies, it should be able to compile 20 years from now, and work consistently across OS versions.

Current Features

  • MQTT 3.1 and 3.1.1
  • Retained messages
  • Wills
  • Native HTTP1 websocket support, without external libraries. HTTP2 will not be implemented. There’s no advantage and it’s overly complex. You can always proxy with Nginx if you really want it.
  • SSL.
  • QoS 0, 1 and 2.
  • Authentication with plugin or ‘mosquitto_password_file’.
  • Native C++ FlashMQ authentication plugin interface.
  • Mosquitto auth plugin version 2 compatibility. This comes with a caveat though: it must be thread safe. Config options exist to perform some serialization, but it’s not a guarantee.
  • Intel SSE4.2 (SIMD) instructions for string/topic handling.
  • Persistent state (save sessions, subscriptions and retained messages).

Roadmap for the 1.0.0 release

  • A lot of testing.

Roadmap for the future

  • MQTT5