Zero Dependencies
All cluster metadata is stored in an embedded Raft consensus engine (openraft + redb), built directly into the broker. One self-contained binary is all you deploy.
What is Danube?
Danube is an open-source messaging platform built in Rust for teams that need reliable pub/sub and streaming without the operational overhead. Built on Tokio and openraft, metadata is replicated through embedded Raft consensus, so there are no external dependencies to deploy or manage.
Producers publish to topics, consumers receive messages via named subscriptions. Choose best-effort dispatch for fire-and-forget workloads or persistent dispatch with at-least-once delivery per topic.
Design Principles
Section titled “Design Principles”One Binary, Three Modes
Run as Standalone for dev, Cluster for production, or Edge for IoT ingestion, all from the same danube-broker binary.
Rust-Native
Built on Tokio for async I/O. No JVM, no GC pauses, no warm-up time. Predictable latency with a memory footprint measured in megabytes.
Cloud-Native Storage
Local WAL for fast writes with background export to S3, GCS, or Azure Blob via OpenDAL. Topics move between brokers without data loss.
Core Capabilities
Section titled “Core Capabilities”- Message Delivery: Topics (partitioned and non-partitioned), best-effort and persistent dispatch with NACK, retry backoff, and dead-letter queues.
- Subscriptions: Exclusive, Shared, Failover, and Key-Shared with per-key ordering via consistent hashing and glob-pattern key filtering.
- Persistence: Local WAL for fast writes, durable segments on shared filesystems or object stores (S3, GCS, Azure). Tiered replay across restarts and broker transfers.
- Schema Registry: Built-in schema management with JSON Schema, Avro, and Protobuf. Version control with backward, forward, and full compatibility enforcement.
- Security: TLS/mTLS encryption, JWT and API-key authentication, fine-grained RBAC with default-deny semantics.
- AI Administration: MCP integration for natural language cluster management via Claude, Cursor, and Windsurf. 40+ tools covering topics, schemas, brokers, diagnostics, and metrics.
- Danube Connect: Plug-and-play connector ecosystem with source connectors (MQTT, HTTP webhooks, databases) and sink connectors (Delta Lake, Qdrant, SurrealDB).
Client Libraries
Section titled “Client Libraries”Danube provides first-class client libraries for four languages:
| Language | Package | Repository |
|---|---|---|
| Rust | danube-client | GitHub |
| Go | danube-go | GitHub |
| Java | danube-java | GitHub |
| Python | danube-client | GitHub |
Next Steps
Section titled “Next Steps” Key Concepts Topics, subscriptions, dispatch strategies, and namespaces.
Quickstart Start a broker and send your first message in under a minute.