[YoshihitoAso]

Summary

close #187

Fix a QBFT timer race that could trigger premature round changes and delay empty-block production.

The empty-block delay callback and PRE-PREPARE acceptance previously reset the round-change timer concurrently. This could leave an untracked timer active after block commitment. Because timeout events carried no block or round information, a stale timeout could affect a subsequent block.

Changes

• Serialize timer management through the consensus event loop.
• Validate timer events against their block number, round, and generation, discarding stale or duplicate events.
• Invalidate delayed proposals and PRE-PREPARE retries when their associated state changes.
• Isolate timer callbacks across Stop/Start cycles.

flowchart LR
    A[Timer expires] --> B[Send internal event]
    B --> C[QBFT event loop]
    D[Receive PRE-PREPARE or other messages] --> C
    E[Block commitment notification] --> C
    C --> F[Check whether the event is still valid]
    F -->|Valid| G[Manage timers and process consensus]
    F -->|Invalid| H[Discard event]

Loading

• Add regression tests covering event ordering, stale timeouts across blocks, proposal replacement, and shutdown/restart.

No public API, wire-format, or configuration changes.

Validation

• go test ./consensus/istanbul/...
• go test -race ./consensus/istanbul/qbft/...
• go test -race ./consensus/istanbul/qbft/core -run '^TestTimer' -count=100

All checks passed.

[Copilot]

Copilot review overview

🟢 Approval recommended

Timer state is serialized, stale events are comprehensively validated, and focused regression tests cover the identified race scenarios.

Review effort: Balanced
Findings: None

What changed in this PR

Refactors QBFT timer handling into the consensus event loop, preventing stale timers from affecting later rounds or blocks.

Changes:

• Adds generation- and view-aware timer events.
• Integrates timer lifecycle with consensus startup, shutdown, and state transitions.
• Adds regression coverage for stale, replaced, duplicated, and restarted timers.

File	Description
core/​timer.go	Implements event-driven timer scheduling and validation.
core/​timer_test.go	Adds timer regression and lifecycle tests.
core/​request.go	Schedules delayed empty-block proposals through timer events.
core/​preprepare.go	Moves deferred PRE-PREPARE retries into the timer system.
core/​handler.go	Integrates timer events with the consensus loop.
core/​events.go	Removes the obsolete timeout event.
core/​core.go	Consolidates timer state and lifecycle management.

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