NATS.FM: What's new in NATS Server v2.11 release

Tomasz Pietrek, Maurice van Veen, and Neil Twigg discuss what’s new in NATS Server v2.11, including:

• Distributed Message Tracing
• Per-Message TTL (Time-To-Live)
• Consumer Priority Groups
• Multi-Message Get (Batch Get)
• Consumer Pause

Episode Summary

Topics covered in this episode include:

1. Distributed Message Tracing

Gain full visibility into message paths across complex NATS topologies — including clusters, gateways, leaf nodes, account boundaries, and subject mappings.

• Activated via a NATS-Trace header and supported directly in the CLI (nats trace $subject).
• Supports dry runs: trace a message’s route without delivering it, ideal for debugging or verification.
• Useful for both operators and developers to understand and verify message flow behavior.

2. Per-Message TTL (Time-To-Live)

Set expiration per message with the NATS-TTL header — allowing messages to age out individually, regardless of stream-level retention settings.

• TTLs are optional and per-message: not all messages need one, and TTL values can differ.
• Backed by an efficient timed hash wheel structure to minimize memory use.
• Major benefits for KV buckets — TTL-based deletion markers reduce storage and avoid manual compaction.

3. Consumer Priority Groups

A new mechanism for pull-based load balancing and resilience:

• Introduces overflow rules: clients can take over message delivery if primary clients are overwhelmed, using thresholds for pending messages or ACKs.
• Pinning: designate a single client to receive all messages until it fails, enabling failover patterns.
• One priority group per consumer in this release, designed to expand in the future.
• Enables simpler, cost-effective cross-region and zone-aware delivery strategies.

4. Multi-Message Get (Batch Get)

Efficient, stateless retrieval of multiple messages from a stream — without creating consumers.

• Supports multiple subject filters, time/sequence bounds, and returns data in sequence order.
• Ideal for querying the latest messages, previewing stream data, or powering internal state lookups.
• Foundational for upcoming KV/Object Store improvements and future batch operations.

5. Consumer Pause

Temporarily halt message delivery without tearing down the consumer or triggering client-side errors.

• Works with both push and pull consumers.
• Specify a pause_until deadline in the config — message flow resumes automatically afterward.
• Heartbeats continue, so clients stay connected and unaware of the pause.
• Valuable for maintenance, orchestration, or preventing unwanted consumption during deployments.

Additional Resources

• Read more about what’s new in v2.11 in the docs
• View the v2.11 release notes on GitHub
• Watch Neil present on NATS Server 2.11 at RethinkConn 2025