Pulsar

Pulsar is a distributed pub-sub messaging platform with a very flexible messaging model and an intuitive client API.

Main features

Horizontally scalable (Millions of independent topics and millions of messages published per second)
Strong ordering and consistency guarantees
Low latency durable storage
Topic and queue semantics
Load balancer
Designed for being deployed as a hosted service:
- Multi-tenant
- Authentication
- Authorization
- Quotas
- Support mixing very different workloads
- Optional hardware isolation
Keeps track of consumer cursor position
REST API for provisioning, admin and stats
Geo replication
Transparent handling of partitioned topics
Transparent batching of messages

Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0