STAN Concepts

    NATS Streaming is a data streaming system powered by NATS, and written in the Go programming language. The executable name for the NATS Streaming server is . NATS Streaming embeds, extends, and interoperates seamlessly with the core NATS platform. The NATS Streaming server is provided as open source software under the Apache-2.0 license. Synadia actively maintains and supports the NATS Streaming server.

    In addition to the features of the core NATS platform, NATS Streaming provides the following:

    • Message/event persistence - NATS Streaming offers configurable message persistence: in-memory, flat files or database. The storage subsystem uses a public interface that allows contributors to develop their own custom implementations.
    • At-least-once-delivery - NATS Streaming offers message acknowledgements between publisher and server (for publish operations) and between subscriber and server (to confirm message delivery). Messages are persisted by the server in memory or secondary storage (or other external storage) and will be redelivered to eligible subscribing clients as needed.
    • Publisher rate limiting - NATS Streaming provides a connection option called that effectively limits the number of unacknowledged messages that a publisher may have in-flight at any given time. When this maximum is reached, further async publish calls will block until the number of unacknowledged messages falls below the specified limit.
    • Rate matching/limiting per subscriber - Subscriptions may specify a option that designates the maximum number of outstanding acknowledgements (messages that have been delivered but not acknowledged) that NATS Streaming will allow for a given subscription. When this limit is reached, NATS Streaming will suspend delivery of messages to this subscription until the number of unacknowledged messages falls below the specified limit.
    • Durable subscriptions - Subscriptions may also specify a “durable name” which will survive client restarts. Durable subscriptions cause the server to track the last acknowledged message sequence number for a client and durable name. When the client restarts/resubscribes, and uses the same client ID and durable name, the server will resume delivery beginning with the earliest unacknowledged message for this durable subscription.

    NATS Streaming provides a rich set of commands and parameters to configure all aspects of the server. Please refer to the for further information on usage, configuration, and administration.