Apache Storm is a free and open source project licensed under the Apache License, Version 2.0

Storm has a large and growing ecosystem of libraries and tools to use in conjunction with Storm including everything from:

  1. Spouts: These spouts integrate with queueing systems such as JMS, Kafka, Redis pub/sub, and more.
  2. storm-state: storm-state makes it easy to manage large amounts of in-memory state in your computations in a reliable by using a distributed filesystem for persistence
  3. Database integrations: There are helper bolts for integrating with various databases, such as MongoDB, RDBMS's, Cassandra, and more.
  4. Other miscellaneous utilities

The Storm documentation has links to notable Storm-related projects hosted outside of Apache.