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test: remove TLS handshake-limit counter race from ConnectionAdmissionTests #229
Description
现象
PR #227 的 PR Quick（run 31996872168）在 Unit Tests 中失败：
TlsHandshakeLimitRejectsTheSecondConnectionWhileTheFirstStalls
Expected to be 1
but found 2
at Assert.That(server.ConnectionAdmission.ActiveConnections).IsEqualTo(1)
ConnectionAdmissionTests.cs:520
#227 没有修改 connection admission 实现或该测试；该覆盖来自已合并的 #162 / PR #209。
竞态窗口
当前测试流程：
using var second = new TcpClient();
await second.ConnectAsync(...);
var secondClosed = await ReadUntilClosedAsync(second);
Ensure(secondClosed, ...);
await Assert.That(server.ConnectionAdmission.ActiveConnections).IsEqualTo(1);但 #162 最终设计明确规定 connection lease 在 terminal cleanup 完成之后才释放，避免慢 dispose 时提前把槽位交给新连接。
因此客户端 ReadUntilClosedAsync(second) 看到 socket 已关闭，并不构成“服务端 terminal cleanup + lease release 已经完成”的同步点。合法时序可以是：
server rejects second
-> closes/disposes transport enough for client to observe EOF
-> client ReadUntilClosedAsync returns
-> server-side terminal cleanup still finishing
-> ActiveConnections temporarily remains 2
-> lease release
-> ActiveConnections becomes 1
PR #227 CI 正好命中了这个窗口。
判断
目前证据更符合 测试同步竞态，不是 admission 产品语义回归：
- [Runtime Architecture][Phase 17] Freeze Generated ABI as API 5 with startup fail-fast for old artifacts #227 未触碰该路径；
- [server][admission] Bound accepted connections and concurrent handshakes #162 / PR feat(server): pre-call connection admission bounds (issue #162) #209 的设计本身要求 release after terminal cleanup；
- 测试把“对端观察到 close”错误地当成“server accounting 已收敛”的 happens-before 条件。
如果后续证明 ActiveConnections 在 terminal cleanup 完成后仍不归 1，再升级为产品 bug。
建议修复
将即时断言改为等待真正需要的服务端状态，例如：
await YieldUntilAsync(
() => server.ConnectionAdmission.ActiveConnections == 1,
"rejected TLS connection must release its connection slot after terminal cleanup");
await Assert.That(server.ConnectionAdmission.ActiveHandshakes).IsEqualTo(1);同时保留 ReadUntilClosedAsync(second)，分别验证：
- 超 handshake limit 的连接确实被立即关闭；
- terminal cleanup 最终把 connection accounting 收敛到 1。
不要用固定 Task.Delay 掩盖窗口。
回归验证
- Linux CI 上循环运行该测试（建议 >= 100 次）。
- 与其它
ConnectionAdmissionTests并行/全套运行，0 flake。 - 若能加 test seam，确定性地阻塞 terminal cleanup，在 client 已观察 close、lease 尚未 release 时证明
ActiveConnections == 2是允许的 transient，再释放 gate 并断言最终归 1。
Activity
SunSi12138 commentedon Aug 17, 2026
已通过 PR #234 修复并合并（merge commit
51b8157c，head2d31d9a）。根因
客户端
ReadUntilClosedAsync观察到 socket 关闭，不等于服务端 terminal cleanup + connection lease release 已经完成（#162 / PR #209 的设计要求 release after terminal cleanup）。因此ActiveConnections在该同步点之后仍可能合法地短暂为 2，即时断言IsEqualTo(1)断言的是瞬态。修复
ConnectionAdmissionTests.TlsHandshakeLimitRejectsTheSecondConnectionWhileTheFirstStalls将即时断言改为收敛等待：保留了
ReadUntilClosedAsync(second)验证"超 handshake limit 的连接被立即关闭"，未引入固定Task.Delay。可选的 test seam 未加：ConnectionSlotStaysHeldUntilTerminalCleanupCompletes已通过 dispose gate 确定性覆盖 release-after-terminal-cleanup 语义。验证证据
25f7cc4，macOS arm64，Release）：单测循环 150 次，114 次失败，失败内容与 PR [Runtime Architecture][Phase 17] Freeze Generated ABI as API 5 with startup fail-fast for old artifacts #227 CI（run31996872168）完全一致。ProtocolHandshakeTimeoutReleasesBothSlots，与本次改动无关，已另开 test: ProtocolHandshakeTimeoutReleasesBothSlots polling budget outruns its own 200ms timeout on fast machines #236 跟踪）。Closes #229。
SunSi12138 commentedon Aug 17, 2026
Fixed by #234 (merged as 51b8157).