GitHub user popduke edited a discussion: [Proposal] Release the First Apache 
BifroMQ (Incubating) Version (4.0.0-incubating)

Since the last non-Incubator release (v3.3.5), BifroMQ has received a number of 
architectural updates, operational improvements, and bug fixes.  
Because many internal components were refactored—and due to the required Apache 
compliance adjustments—this release is **not backward-compatible** with 
previous non-Incubator versions. Users should plan this as a **major upgrade**.

**About the version number:**  
The `4.0.0-incubating` version number reflects continuity from the 
pre-Incubator lineage while marking a new phase under the Apache Incubator.

Below is a brief summary of what the 4.0.0-incubating release contains.

## 1. Major New Features

- **Support for “Independent Workload Cluster (IWC)” deployment mode**  
  Enabling MQTTServer, DistService, InboxService, RetainService, 
SessionDictService, and APIServer to run as separate workload clusters for 
improved scaling and resource isolation.

- **New Plugin: `ClientBalancer`**  
  Allows integrating custom client-balancing strategies to manage MQTT client 
connection distribution more effectively.

- **New SPIs and Hook Points for Deep Customization**  
  Multiple new extension points at different levels have been added to support 
advanced integration and extension use cases.

- **New APIs for Cluster Landscape Inspection, RPC Traffic Governance, and 
StoreBalancer Management**  
  These APIs provide better visibility into cluster composition, more control 
over store-balancing behavior, and the ability to govern internal RPC traffic 
patterns.

## 2. Improvements in Architecture and Core Capabilities

- **Various improvements to base-cluster and base-crdt** for reduced overhead 
and faster convergence.

- **Refactored base-rpc** to support more graceful rebalancing behavior and 
reduce disruption during topology changes.

- **Refactored base-kv** to improve resilience and make the system more 
pluggable and extensible.

- **Refactored base-scheduler** with improved observability and easier 
customization of scheduling logic.

- **Optimized internal RPC protocol and storage schemes** across DistService, 
InboxService, and RetainService for better load distribution and more 
predictable performance.

## 3. Apache Compliance Work

- Updated **LICENSE** and **NOTICE** with correct third-party attributions.  
- Normalized source headers and Java package paths under `org.apache.bifromq`.  
- Added **DISCLAIMER** and other ASF-required metadata.  
- Updated build and distribution scripts to produce Apache-compliant source 
releases.  
- Updated SSL/TLS handling: the default build does **not** bundle any SSL 
implementation; users may optionally build variants with their preferred SSL 
library.

## 4. Next Steps

- Keep this discussion open for feedback for **approximately one week**.  
- Prepare the **4.0.0-incubating RC1** and upload it to the ASF dev 
distribution area.  
- Initiate the **[VOTE]** thread on `dev@` once the review window closes.  
- Address any findings and iterate with additional RCs if necessary.

Feedback on this proposal and on the summarized changes is welcome.

GitHub link: https://github.com/apache/bifromq/discussions/192

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