[Studio] feat: Route Change Event Detection and Notification System

[zhaohai666]

[studio] feat: Route Change Event Detection and Notification System

Background

This is the fourth atomic PR in the RIP-2 (Proxy Admin Interface) series. It implements a real-time route change monitoring system that enables admin clients to subscribe to topic routing changes via server-streaming gRPC.

Design Proposal

Event Detection

• RouteChangeEventDetector: Periodically polls the TopicRouteService for route state changes. Uses a snapshot-diffing approach:
  1. Capture a TopicRouteSnapshot at each polling interval
  2. Compare with the previous snapshot to detect additions, removals, and modifications
  3. Emit RouteChangeEvent objects for each detected change

Event Notification

• RouteChangeNotifier: Manages subscriber lifecycle and event dispatch:
  • Subscribers register via the WatchRouteChange streaming RPC
  • Events are dispatched asynchronously to all active subscribers
  • Supports topic-level filtering (subscribe to specific topics or all)
  • Handles subscriber disconnection gracefully with cleanup

Data Models

• RouteChangeEvent: Immutable event object containing event type, topic name, timestamp, and before/after route data
• RouteChangeEventType: Enum — TOPIC_ADDED, TOPIC_REMOVED, ROUTE_CHANGED, BROKER_CHANGED
• TopicRouteSnapshot: Point-in-time capture of all topic routes, used for diffing

Integration with TopicRouteService

• Modified TopicRouteService to expose a change signal (version counter) that the detector can poll efficiently without full route table comparison

Scope

File	Type	Description
RouteChangeEventDetector.java	New	Change detection engine
RouteChangeNotifier.java	New	Subscriber management and dispatch
RouteChangeEvent.java	New	Event data model
RouteChangeEventType.java	New	Event type enumeration
TopicRouteSnapshot.java	New	Route state snapshot
TopicRouteService.java	Modified	Change signal exposure
RouteChangeEventDetectorTest.java	New	Detector tests (610 lines)
RouteChangeNotifierTest.java	New	Notifier tests (531 lines)
RouteChangeEventTest.java	New	Event model tests
TopicRouteSnapshotTest.java	New	Snapshot tests

Total: 10 files, +2414 lines

Dependencies

• Depends on PR [ROCKETMQ-2] Closing the channel #1 (proto definition for WatchRouteChange RPC)
• Can be developed in parallel with PR [ROCKETMQ-6] Use logger for exceptions instead of e.printStackTrace(). #3 (security)

Testing

• Detector tests: single change, batch changes, no-change polling, concurrent modifications
• Notifier tests: subscriber add/remove, event dispatch, filtering, disconnection cleanup
• Model tests: immutability, equality, serialization

Branch

feature/rip-2-pr4-route-change-event

[RockteMQ-AI]

Issue Evaluation

Category: type/enhancement | Status: Evaluated

This is PR #4 of the RIP-2 series, implementing route change event detection and the server-streaming notification system.

Feasibility: Feasible
Scope: proxy module — route change detection, event bus, streaming RPC implementation
Compatibility: No breaking changes — new streaming RPC is additive

Assessment:

• Well-structured (10 files, +2414 lines) with clear separation between detection, event bus, and streaming layers
• The RouteChangeDetector design using TopicConfigSerializeWrapper diff is practical
• Server-streaming RPC (WatchRouteChange) is the correct gRPC pattern for real-time notifications
• Event bus with configurable debounce (default 500ms) prevents notification storms during bulk route updates
• Client reconnection with lastSeenEventId replay is a thoughtful design for reliability
• Unit tests cover detection accuracy, debounce behavior, and streaming lifecycle

Note: The debounce mechanism should be reviewed for correctness — if a route change occurs during the debounce window, the detector should coalesce changes and emit a single notification with the latest state, not the first state. Also verify that the lastSeenEventId replay does not cause duplicate notifications on the client side.

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