RabbitMQ

RabbitMQ is an open source, multi-protocol messaging and streaming broker. Applications exchange messages through it over AMQP 1.0 and AMQP 0-9-1, MQTT, STOMP, and the RabbitMQ Stream Protocol, so producers and consumers can speak whichever protocol suits them.

For reliability it offers quorum queues, a replicated queue type tuned for data safety and consistency, alongside streams: a persistent, replicated, append-only log with non-destructive consumer semantics. MQTT and STOMP are also available over WebSocket for browser clients.

Built on Erlang/OTP, RabbitMQ supports clustering, a Kubernetes Cluster Operator, CLI tools, and Prometheus and Grafana monitoring. It is licensed under the Mozilla Public License 2.0, with commercial support and editions available from Broadcom through VMware Tanzu RabbitMQ.