Zenoh Backend redb

A Zenoh storage backend using redb as the underlying database engine.

Overview

This backend provides persistent storage for Zenoh using redb, a pure Rust embedded key-value database with ACID compliance and zero-copy reads. It's particularly well-suited for edge computing, IoT devices, and applications requiring a lightweight, dependency-free storage solution.

Compatible with Zenoh 1.7.0

Features

• Pure Rust - No C dependencies, fully memory-safe
• High Performance - Zero-copy reads with MVCC support, thread-local buffers
• ACID Compliant - Reliable data storage with transaction support
• Wildcard Queries - Supports Zenoh wildcard patterns (* and **)
• Flexible Configuration - Per-storage configuration options
• Read-Only Mode - Optional read-only storage instances
• Prefix Stripping - Efficient key storage with optional prefix removal
• Embedded - No separate database server required
• Persistent - Data survives zenohd restarts

Installation

1. Build the plugin library:

cargo build --release --features plugin

2. Install the plugin in your Zenoh plugin directory:

cp target/release/libzenoh_backend_redb.so ~/.zenoh/lib/

Quick Start

1. Configure Zenoh to use the backend in your zenoh.json5 config file:

{
  plugins: {
    storage_manager: {
      volumes: {
        redb: {}
      },
      storages: {
        demo: {
          key_expr: "demo/example/**",
          strip_prefix: "demo/example",
          volume: {
            id: "redb",
            dir: "demo_storage",
            create_db: true,
            fsync: true
          }
        }
      }
    }
  }
}

2. Start Zenoh with the configuration:

zenohd -c zenoh.json5

Configuration

Storage Configuration

Each storage instance can be individually configured:

Parameter	Type	Default	Description
dir	String	required	Database directory name (creates <name>.redb)
db_file	String	-	Alternative to dir, explicit database filename
cache_size	Number	redb default	Cache size in bytes
fsync	Boolean	true	Enable fsync for durability
create_db	Boolean	true	Create database if it doesn't exist
read_only	Boolean	false	Read-only mode

Environment Variables

• ZENOH_BACKEND_REDB_ROOT: Override default storage directory (default: ~/.zenoh/zenoh_backend_redb)

Usage Examples

Basic Storage Configuration

{
  plugins: {
    storage_manager: {
      volumes: {
        redb: {}
      },
      storages: {
        sensor_data: {
          key_expr: "sensor/**",
          volume: {
            id: "redb",
            dir: "sensors",
            fsync: true
          }
        }
      }
    }
  }
}

Multiple Storages

{
  plugins: {
    storage_manager: {
      volumes: {
        redb: {}
      },
      storages: {
        sensors: {
          key_expr: "sensor/**",
          volume: {
            id: "redb",
            dir: "sensor_db"
          }
        },
        config: {
          key_expr: "config/**",
          volume: {
            id: "redb",
            dir: "config_db"
          }
        }
      }
    }
  }
}

Using Strip Prefix

Strip prefix saves storage space by removing the common prefix from stored keys:

{
  plugins: {
    storage_manager: {
      volumes: {
        redb: {}
      },
      storages: {
        demo: {
          key_expr: "demo/example/**",
          strip_prefix: "demo/example",
          volume: {
            id: "redb",
            dir: "demo_storage"
          }
        }
      }
    }
  }
}

Read-Only Storage

{
  plugins: {
    storage_manager: {
      volumes: {
        redb: {}
      },
      storages: {
        archive: {
          key_expr: "archive/**",
          volume: {
            id: "redb",
            dir: "archive_db",
            read_only: true
          }
        }
      }
    }
  }
}

Custom Cache Size

{
  plugins: {
    storage_manager: {
      volumes: {
        redb: {}
      },
      storages: {
        large_data: {
          key_expr: "large/**",
          volume: {
            id: "redb",
            dir: "large_db",
            cache_size: 104857600  // 100 MB cache
          }
        }
      }
    }
  }
}

Architecture

┌─────────────────────────────────────┐
│       Zenoh Application             │
└────────────┬────────────────────────┘
             │
             ↓
┌─────────────────────────────────────┐
│      RedbBackend                    │
│  - Manages multiple storages        │
│  - Configuration management         │
└────────────┬────────────────────────┘
             │
             ↓
┌─────────────────────────────────────┐
│      RedbStorage                    │
│  - CRUD operations                  │
│  - Wildcard matching (* and **)     │
│  - Dual-table design                │
└────────────┬────────────────────────┘
             │
             ↓
┌─────────────────────────────────────┐
│         redb Database               │
│  - ACID transactions                │
│  - MVCC                             │
│  - Zero-copy reads                  │
└─────────────────────────────────────┘

Comparison with Other Backends

Feature	redb	RocksDB	LMDB
Pure Rust	Yes	No (C++)	No (C)
ACID	Yes	Yes	Yes
Zero-copy reads	Yes	No	Yes
Concurrent writes	MVCC	Yes	Limited
Memory-mapped	Yes	No	Yes
Setup complexity	Simple	Moderate	Moderate
Best for	Edge/Embedded	High-throughput	Read-heavy

Testing

Run unit and integration tests (excludes zenohd tests):

just test

zenohd Integration Tests

The zenohd integration tests verify the full plugin lifecycle:

• Plugin loading in zenohd
• PUT/GET/DELETE operations
• Wildcard queries (* and **)
• Data persistence across zenohd restarts

Requirements: The tests require zenohd and the storage_manager plugin to be built with the exact same Zenoh version and Rust compiler as the redb plugin.

# Recommended: Use Podman for version-matched testing
just docker-test-zenohd

# Local testing (requires matching zenohd 1.7.0 + plugins in ~/.zenoh/lib/)
just test-zenohd

The Docker method builds zenohd and all plugins from source with matching versions, ensuring compatibility.

Development

# Install development tools
just install-tools

# Format and lint
just check

# Run all quality checks
just quality

# Pre-commit verification
just verify

License

This project is licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• Eclipse Public License 2.0 (LICENSE-EPL or https://www.eclipse.org/legal/epl-2.0/)

at your option.

Resources

• Zenoh Website
• Zenoh Documentation
• redb Documentation
• Zenoh GitHub
• redb GitHub

Status

This project is currently in alpha stage. The API may change as we gather feedback and improve the implementation.