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leebradley authored and Geal committed e102b99 Jun 29, 2020


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Sōzu · Join the chat at Build Status

Sōzu is a lightweight, fast, always-up reverse proxy server.

Why use Sōzu?

  • Hot configurable: Sozu can receive configuration changes at runtime through secure unix sockets.
  • Upgrades without restarting: Sozu is always-up, meaning it upgrades itself while still processing requests.
  • Handles SSL: Sozu handles SSL, so your backend servers can focus on what they do best.
  • Protects your network: Sozu protect backends by shielding them behind the reverse proxy, limiting direct network access. Sozu uses Rust, a language primed for memory safety. And even if a worker is exploited, sozu workers are sandboxed.

Building and starting


  • openssl 1.0.1 or above (including libraries/includes, ie apt install libssl-dev / rpm install openssl-devel

You can create the required executables like this:

cd ctl && cargo build; cd ../bin && cargo build

This will create the sozu executable for the reverse proxy, and sozuctl to command it.

To start the reverse proxy:

cd bin;
../target/debug/sozu start -c config.toml

You can edit the reverse proxy's configuration with the config.toml file. You can declare new applications, their frontends and backends through that file, but for more flexibility, you should use the command socket (you can find one end of that unix socket at the path designed by command_socket in the configuration file).

sozuctl has a few commands you can use to interact with the reverse proxy:

  • soft shutdown (wait for active connections to stop): sozuctl -c config.toml shutdown
  • hard shutdown: sozuctl -c config.toml shutdown --hard
  • display the list of current configuration messages: sozuctl -c config.toml state dump
  • save the configuration state to a file: sozuctl -c config.toml state save -f state.json

For OSX build

Mac OS uses an old version of openssl, so we need to use one from Homebrew:

brew install openssl
brew link --force openssl

If it does not work, set the following environment variables before building:

export OPENSSL_LIB_DIR=/usr/local/opt/openssl/lib/
export OPENSSL_INCLUDE_DIR=/usr/local/opt/openssl/include/


The reverse proxy uses env_logger. You can select which module displays logs at which level with an environment variable. Here is an example to display most logs at info level, but use trace level for the HTTP parser module:

RUST_LOG=info,sozu_lib::parser::http11=trace ./target/debug/sozu

Exploring the source

  • lib/: the sozu_lib reverse proxy library contains the event loop management, the parsers and protocols
  • bin/: the sozu executable wraps the library in worker processes, and handle dynamic configuration
  • ctl/: the sozuctl executable can send commands to the reverse proxy


Copyright (C) 2015-2018 Geoffroy Couprie, Clément Delafargue and Clever Cloud

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, version 3.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.


Sōzu HTTP reverse proxy, configurable at runtime, fast and safe, built in Rust. It is awesome! Ping us on gitter to know more





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