Sōzu

Spec sheet

Purpose

Sōzu is an open-source TCP and HTTP reverse proxy built in Rust for demanding, dynamic web infrastructures.Read 8 Oct 2026 · sozu.io

Product

Sōzu is an open source TCP and HTTP reverse proxy built in Rust for highly demanding web infrastructure.Read 8 Oct 2026 · sozu.io

Intended users

The maker describes Sōzu as used by cloud and PaaS providers to manage changing web infrastructure and frequent app and customer additions.Read 8 Oct 2026 · sozu.io

Deployment

The project publishes Linux binaries and Docker images for tagged releases and also documents building from source.Read 8 Oct 2026 · github.com

Security

The project describes Rust as providing memory safety and says Sōzu workers are sandboxed, with backends shielded behind the proxy.Read 8 Oct 2026 · github.com

License

Sōzu is covered by the GNU Affero General Public License version 3.0 and above; the maker says businesses based on Sōzu should contribute back or contact Clever Cloud for a business agreement.Read 8 Oct 2026 · sozu.io

Headquarters

Nantes, FranceRead 28 Sep 2026 · sozu.io

Control plane

External tools communicate with the main process through a Unix socket using a Protocol Buffers based binary protocol, and configuration is applied as atomic diffs.Read 8 Oct 2026 · sozu.io

Dynamic configuration

Sōzu applies configuration changes at runtime without reloading and supports multiple updates per second.Read 8 Oct 2026 · sozu.io

High availability

Sōzu is designed to stay up while it upgrades itself and to avoid losing connections during configuration changes and binary upgrades.Read 8 Oct 2026 · sozu.io

Installation

The project README says prebuilt binaries are available for Linux and Docker images are published for tagged releases.Read 8 Oct 2026 · github.com

Limits

The project says Sōzu uses fixed resource and connection limits to help avoid out-of-memory kills and increased latency under high connection counts.Read 8 Oct 2026 · sozu.io

Load balancing

It detects broken backend servers and supports Round Robin, Random, Least_loaded, and Power of two load balancing algorithms.Read 8 Oct 2026 · sozu.io

Logging

Its logger can send logs to stdout, files, TCP, UDP, and Unix sockets.Read 8 Oct 2026 · sozu.io

Metrics

Metrics can be sent using a StatsD compatible protocol or aggregated locally for querying through the configuration socket.Read 8 Oct 2026 · sozu.io

Release verification

The project README says releases include SHA256 checksums, sigstore keyless signatures, and SLSA build provenance attestations for tarballs.Read 8 Oct 2026 · github.com

Resource limits

Sōzu uses fixed resource and connection limits to help avoid out of memory kills and increased latency under high connection counts.Read 8 Oct 2026 · sozu.io

Runtime configuration

It applies configuration changes at runtime without reloading, including atomic configuration diffs through a Unix socket using a Protocol Buffers based protocol.Read 8 Oct 2026 · sozu.io

Support contact

The site’s legal notice lists [email protected] for general support.Read 8 Oct 2026 · sozu.io

TLS

Sōzu can act as a TLS endpoint and supports ring, AWS-LC, and OpenSSL cryptographic backends at compile time.Read 8 Oct 2026 · github.com

Upgrades

Its main process and worker model is designed to allow upgrades while continuing to process requests.Read 8 Oct 2026 · sozu.io

Where Specifiction places it

• Reverse Proxy Software#28 of 336.8