fix(raft): electionLoop 复用 timer, 按 Stop→drain→Reset 顺序更新

[NeverENG]

Summary

• `NewRaftWithDataDir` 内 `time.NewTimer` 一次性初始化 `r.timer`
• `electionLoop` 不再每轮 `time.NewTimer`, 只 select; reset 由独立 `resetElectionTimer` 处理
• `resetElectionTimer` 用标准三步: `Stop()` → 必要时 drain `timer.C` → 重新随机 `electionTimeout` → `Reset`

Background

原代码 `for { r.timer = time.NewTimer(timeout); select{...} }` 每轮新建 timer, GC 压力 + 偶发的旧 timer fire 写入新 timer 的 channel 风险。改为复用单一 timer + 标准 Stop/drain/Reset 序列, 符合 Go 官方 timer.Reset 文档建议。

Test plan

• `go build ./Raft/...` 通过
• `go vet ./Raft/...` 通过
• raft_test.go 14 用例全部通过 (清掉残留 raft_data/raft_test_data_* 后), 含 `TestElectionTimeout`

🤖 Generated with Claude Code

Summary by CodeRabbit

• Refactor
  • Optimized election timer handling in the Raft consensus mechanism for improved efficiency and reliability. Single reusable timer now replaces repeated timer creation, reducing resource usage and enhancing election timing accuracy.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 28d4ef37-5e56-445b-b8e7-efbe1d35ad0f

📥 Commits

Reviewing files that changed from the base of the PR and between bfff8bc and 0b0c854.

📒 Files selected for processing (1)

• Raft/raft.go

---

📝 Walkthrough

Walkthrough

Election timer management is refactored from allocating a fresh timer on each loop iteration to reusing a single timer object. The constructor initializes the timer, and the election loop uses, resets, and re-arms it across multiple cycles while properly draining stale signals.

Changes

Election Timer Reuse

Layer / File(s)	Summary
Timer initialization in constructor Raft/raft.go	Constructor creates a reusable election time.Timer with the initial randomized election timeout immediately after commitCond setup.
Election loop with reusable timer Raft/raft.go	electionLoop selects on the shared timer channel and calls resetElectionTimer after election start or receiving heartbeat/election signals. resetElectionTimer performs Stop→drain→randomize→Reset to maintain consistent election timing and avoid spurious wakeups.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 A timer born, then reused with care,
No more wasteful cycles in the air,
Stop, drain, reset—a rhythm so fair,
Elections tick in the Raft's affair! 🎪

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/raft-timer

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}