Disque
Disque is a distributed message broker
...The design focuses on simplicity, providing a minimal and clear API for producers to enqueue jobs (messages) and consumers to process them, while handling replication, failure and re-queueing internally. Disque supports multi-master clusters where any node can serve producers and consumers, and messages are asynchronously replicated to a configurable number of nodes to ensure availability even in the face of failures. It offers both at-least-once and at-most-once delivery semantics depending on per-message configuration, and retries or re-queueing of un-acknowledged jobs are built in. ...