mq-bridge

crossing streams · library

One Rust engine to move data reliably between brokers, databases, files and HTTP — embedded in your Rust, Python or Node.js service.

🖥️ mq-bridge-app · 📊 ETL benchmarks · 🏗️ Architecture · ⚙️ Config · 📚 Middleware & endpoint reference

What is mq-bridge?

mq-bridge is an asynchronous Rust library that moves messages and data between systems: Kafka, NATS, RabbitMQ, MQTT, MongoDB, PostgreSQL/MySQL/SQLite, Postgres CDC, ClickHouse, Redis Streams, HTTP, WebSocket, gRPC, ZeroMQ, AWS SQS/SNS, IBM MQ, cloud object storage, files, and in-memory channels. Every endpoint sits behind the same batch-shaped receive_batch / send_batch traits, so any source can feed any sink.

A route connects one input to one output. In between, it can transform, filter, fan out, retry, rate-limit, deduplicate, or answer a request, all by configuration. Where configuration isn't enough, you add a handler in Rust, Python or Node.js. Batching, ack/nack, commit ordering and broker I/O stay in the Tokio-based core, so your code works with plain CanonicalMessages and doesn't handle Kafka offsets or AMQP nacks.

It is a library you embed in your own service, not a daemon or platform you operate. If you'd rather not write code, mq-bridge-app runs the same engine and config as a CLI, server, desktop app, and MCP server.

Use cases

Problem	Guide with a runnable example
A RAG or semantic-search index drifts from its Postgres source	Keep a vector index in sync with Postgres: CDC → embeddings → Qdrant
A service must update its database and publish an event atomically	Transactional outbox with Postgres and Kafka
Tests for Kafka, NATS or RabbitMQ consumers need a running broker	Test message handlers without a broker

Quick Start

Install the library for your language:

Language	Package	Install
Rust	mq-bridge	cargo add mq-bridge --features kafka,nats,yaml
Python	mq-bridge (PyPI)	pip install mq-bridge
Node.js	mq-bridge (npm)	npm install mq-bridge

Describe a route — here Kafka → NATS with retries — in routes.yaml:

kafka_to_nats:
  input:
    kafka: { url: "localhost:9092", topic: "orders", group_id: "bridge" }
  output:
    middlewares:
      - retry: { max_attempts: 5 }
    nats: { url: "nats://localhost:4222", subject: "orders.processed" }

Run it:

from mq_bridge import Route
Route.from_file("routes.yaml", "kafka_to_nats").run()  # blocks; use start() to keep going

import { Route } from "mq-bridge";
Route.fromFile("routes.yaml", "kafka_to_nats").start();

mq_bridge::deploy_file("routes.yaml").await?; // every route in the file, in the background

Attach a handler (with_handler / withHandler) when you need business logic in between. No code at all? mq-bridge-app runs the same engine from the command line or a desktop UI:

mqb copy 'kafka://localhost:9092?topic=orders' 'nats://localhost:4222?subject=orders.processed'

Capabilities at a glance

Every row works from the Rust crate, the Python and Node.js packages, and the zero-code app; the Cargo feature is only needed when you build the Rust crate yourself. The linked book documents the library as well as the app.

Capability	How (endpoint / middleware · Cargo feature)	Docs
Message brokers: Kafka, NATS (JetStream), RabbitMQ (AMQP), MQTT, Redis Streams, AWS SQS/SNS, IBM MQ, ZeroMQ	kafka, nats, amqp, mqtt, redis_streams, aws, ibmmq, zeromq endpoints · features kafka, nats, amqp, mqtt, redis-streams, aws, ibm-mq, zeromq	Connectors
Change Data Capture (CDC): stream Postgres or MongoDB changes to Kafka, files, a warehouse, …	postgres_cdc (logical replication, pgoutput) · postgres-cdc; mongodb with consume: capture_all / capture_new (change streams) · mongodb	Postgres CDC tutorial · MongoDB
SQL databases: PostgreSQL, MySQL, MariaDB, SQLite as source (cursor polling) or sink (insert / upsert)	sqlx endpoint · sqlx	PostgreSQL / MySQL / SQLite · Upserts
MongoDB as source or sink	mongodb endpoint · mongodb	MongoDB
ClickHouse bulk insert and resumable reads	clickhouse endpoint · clickhouse	ClickHouse
Search engines and other bulk document APIs (Meilisearch, Typesense, Elasticsearch, Qdrant, PostgREST / Supabase)	http_bulk endpoint · http-bulk	HTTP bulk
Object storage: S3 (and S3-compatible, e.g. R2), GCS, Azure Blob, or a local directory, as Parquet, JSONL or CSV	object_store endpoint with format: parquet | raw | json | csv · object-store, parquet	Object storage
Files: CSV and JSONL, read and write	file endpoint · built in	File
Analytics / warehouses: Snowflake, BigQuery, Databricks / Spark, Athena / Trino, DuckDB via Parquet on S3/GCS/Azure. These are not native connectors: mq-bridge writes the Parquet files, the warehouse loads or queries them	object_store with format: parquet · parquet	Snowflake · BigQuery · Databricks / Spark · Athena / Trino · DuckDB
HTTP, gRPC, WebSocket as server or client, including request/reply	http, grpc, websocket endpoints · http, grpc, websocket	HTTP · gRPC · Request / reply
Schema validation and type coercion (JSON Schema subset, field mapping)	transform middleware · built in	Transform & schema mapping
Reliability: retries, dead-letter queue, deduplication, rate limiting	retry, dlq, deduplication, limiter middleware · dedup for deduplication	Middleware reference · Delivery guarantees
Broker-free tests: run a route or handler against in-memory channels, no Docker	memory endpoint · built in	Embed the library
ETL without code	mq-bridge-app: mqb copy <from> <to>, YAML routes, desktop UI, MCP server	Quick start: mqb copy
More systems through plugins: Apache Pulsar, Meilisearch, and Redpanda Connect's inputs, outputs and processors	native plugins · plugin	Plugin endpoints · Connect plugin: inputs, outputs, processors

The Connect plugin links only Redpanda Connect components free of Redpanda Community License code (bundled code is Apache-2.0 and MIT), so some upstream components, such as its Kafka, AWS and Snowflake ones, are not included; see what is not included.

For AI agents: llms.txt is a curated index of the documentation.

Benchmarks

Like-for-like ETL comparisons, measured through the zero-code mq-bridge-app; every number, baseline and command is in the ETL benchmark harness:

Scenario	mq-bridge	Compared with
CSV → JSONL, 1M mixed-type rows (~116 MiB)	3,134,796 rows/s, ~29 MiB RAM	Meltano (tap-csv → target-jsonl): 9,771 rows/s, ~444 MiB RAM — mq-bridge ~321x faster DuckDB, all cores: 2,109,704 rows/s — mq-bridge ~1.5x faster, ~18x less memory
Kafka → file, 1M rows, no transform	878,105 rows/s, ~160 MiB RAM	Sea Streamer, mimalloc build: 492,465 rows/s, ~894 MiB RAM — mq-bridge ~1.8x faster (also ~1.8x vs. its default-allocator build)

The CSV row reuses an existing, independently published 1M-row CSV → JSONL workload, on a byte-identical fixture: 7 mixed-type columns, seed 42, 121,981,421 bytes, SHA-256 a84894e0…0c45b221 (full definition). Whole-process wall-clock, no transformation, Meltano run on the same machine and file.

All figures: mq-bridge 0.4.20. DuckDB is a throughput ceiling for the conversion itself, not an ETL tool.

External benchmark: both the Rust library (mq-bridge) and the Python binding (mq-bridge-py) are entries on the third-party http-arena.com leaderboard, which compares HTTP frameworks by requests per second (live, so rankings shift over time). It measures mq-bridge's HTTP (and WebSocket) serving path, which is one endpoint among many, not broker or ETL throughput; those are covered under Benchmarks. See the Python analysis notes for the local comparison harness.

Why mq-bridge

What you get from one engine, whichever language you call it from:

• 16+ native transports, 100+ more via plugin, one API: every connector listed above, plus dir_spool (a crash-safe directory FIFO queue), behind the same receive_batch / send_batch shape.
• Redpanda Connect reach: the Connect plugin adds Redpanda Connect's production-proven components — 56 inputs and 68 outputs as endpoints, plus 86 processors, most of which also run as middleware on any endpoint — while mq-bridge keeps routing, batching, retries, DLQ and deduplication.
• Change Data Capture: stream row-level changes from Postgres (logical replication / pgoutput) and MongoDB (change streams) as flat rows with an operation marker.
• Restart-safe delivery: batch-aware ack/nack with commit sequencing for cumulative-ack brokers; the integration suite shows no data loss during in-flight broker restarts, including a Postgres CDC restart-safety test.
• Reliability middleware, not a framework: retries, dead-letter queues, deduplication, rate limiting, and cookie/session persistence wrap any endpoint.
• Polyglot on one engine: the same Rust core ships as native Python and Node.js bindings; routing, batching, and broker I/O stay in Rust.
• TLS everywhere, one config shape: a single TlsConfig block (CA bundle, client cert/key for mTLS, insecure-skip) is reused across transports.
• Self-hosted, no daemon: generate config in the optional UI, paste it into your code, run it in-process. No hosted control plane, no separate scheduler.

Prefer not to write code? mq-bridge-app runs the exact same engine as a standalone, zero-code ETL service configured entirely by YAML or environment variables. It ships a Postman-style UI to build, send, and inspect messages against a route, and can import Postman collections and AsyncAPI documents to scaffold routes and endpoints. Everything about the app — install, CLI, UI, cookbook, tuning — is in the 📖 book.

When to use mq-bridge

• Hybrid Messaging: Connect systems speaking different protocols (e.g., MQTT to Kafka) without writing a custom adapter for every pair.
• Batch-heavy Pipelines: Increase throughput by moving messages in batches while keeping per-message ack/nack decisions.
• Infrastructure Abstraction: Write business logic against CanonicalMessages and swap the underlying transport later.
• Resilient Pipelines: Apply retry, DLQ, deduplication, limiter, and cookie/session behavior consistently around endpoints.
• Database Integration: Combine databases with message brokers, for example by ingesting messages into SQL/MongoDB or forwarding outbox rows to a broker.
• Sidecar / Gateway: Run the bridge beside another service to ingest, filter, and route messages before they reach the core application.

When NOT to use mq-bridge

• Stateful Stream Processing: For windowing, joins, or complex aggregations over time, dedicated stream processing engines are more suitable.
• Domain Aggregate Management: If you need a framework to manage the lifecycle, versioning, and replay of domain aggregates (Event Sourcing), use a specialized library. mq-bridge handles the bus, not the entity.
• Protocol-Specific Power Features: mq-bridge intentionally exposes a common subset: publish/consume, pub/sub where possible, request-reply where possible, batching, middleware, and ack/nack handling. If your application depends on highly specific broker features, using that broker's native client directly may be better.

Documentation

The 📖 mq-bridge book covers the library and the app. Connectors, middleware and tuning use the same settings in both.

I want to…	Read
Embed the library, write handlers, publish from code	Quick start: library · Embed the library · Bindings API · docs.rs
Move data without code	Quick start: mqb copy · Desktop UI · CLI · MCP server
Configure a connector	Connectors, with YAML and URL examples for each
Know what each backend supports (subscriber mode, request-reply, nack, CDC vs. polling)	Overview & capabilities
Add retries, DLQ, dedup, transform, routing	Cookbook · Middleware & structural endpoints
Understand delivery guarantees and idempotent sinks	Delivery guarantees
Build request/reply or CQRS-style flows	Request / reply · Embed the library: CQRS
Tune throughput	Performance tuning
Write my own endpoint, middleware or plugin	EXTENDING.md · PLUGINS.md
Understand the internals	ARCHITECTURE.md · CONFIGURATION.md

Status

mq-bridge was created in 2025. Its reliability behavior is exercised by an automated integration and performance suite across supported endpoints, in each of the queue and subscriber modes that endpoint supports:

• All endpoints showed no data loss during in-flight broker restarts; MQTT publish confirmation was hardened until a chaos test drove in-flight loss to zero.
• Postgres CDC has a restart-safety test: an un-acked, in-flight batch is redelivered after a database restart with no loss and no gap.

It is used as rust library in armature and as python lib in omniload.

Running Tests

The project includes integration and performance tests. Most backend tests require Docker.

To run the performance benchmarks for all supported backends:

cargo test --test integration_test --release -- --ignored --nocapture --test-threads=1

To run the criterion benchmarks:

cargo bench --features "full"

Criterion numbers vary with the machine they run on; for comparable throughput figures use the integration performance test above, or see the ETL benchmarks.

Contributing

Contributions are welcome. See CONTRIBUTING.md for setup notes, code style, and pull request guidelines.

AI Disclaimer

This library was written with a lot of AI assistance. The core started as my own code; many endpoints and docs were expanded with Gemini, CodeRabbit, Claude, and Codex, which made adding transports much faster once the endpoint traits were stable.

Generated code can look plausible while missing important details, so I review every commit manually, clean up and refactor the output, and rely on the integration suite to catch regressions. I trust the current code as much as if I had written it myself. Given the large feature set there may still be open issues; the current focus is testing and documentation.

License

mq-bridge is dual-licensed under either the MIT license or the Apache License, Version 2.0, at your option.

Binary distributions carry their applicable third-party terms in THIRD_PARTY_LICENSES.txt. Their current maintenance process is documented in docs/THIRD_PARTY_LICENSES.md.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in mq-bridge by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.