RabbitMQ

RabbitMQ is an open-source message broker that implements the Advanced Message Queuing Protocol (AMQP). It enables applications to communicate by sending messages through a broker rather than making direct synchronous calls, supporting asynchronous, decoupled architectures. The server runs on the Erlang virtual machine and is designed to be scalable, reliable, and feature-rich across varied deployment environments.

Core messaging model: Producers publish messages to exchanges, from which a routing decision places messages into one or more queues. Consumers retrieve messages from queues. Exchanges implement routing rules and come in several types, including direct, fanout, topic, and headers. Messages can be marked durable and persisted to disk to survive broker restarts, and deliveries can be acknowledged by consumers to ensure reliability. The system supports features such as message TTL, dead-lettering, and selective acknowledgments.

Reliability and scaling: RabbitMQ supports acknowledgments, publisher confirms, and transactions to improve delivery guarantees. It offers high-availability options such as replicated queues in older setups and quorum queues that are fully replicated across nodes. Clustering enables scale-out, while virtual hosts provide multi-tenant isolation within a single broker deployment.

Administration and ecosystem: A management plugin provides a web-based UI and HTTP API to monitor and manage brokers, queues, exchanges, and bindings. Official client libraries exist for many languages, including Java, Python, JavaScript, .NET, and Go. RabbitMQ can be deployed on-premises, in virtualized or cloud environments, and is commonly run in containers and orchestrated with Kubernetes. Plugins extend protocol support and functionality.

Use cases: It is widely used for decoupled microservices communication, asynchronous task queues, event distribution, and reliable background processing.