[BUG] Poison Wait alert fires incorrectly when wait value is 0ms (false positive)

[tdinh2011]

Component

Lite

Performance Monitor Version

2.1.0

SQL Server Version

SQL Server 2019 CU32 GDR

Windows Version

Windows Server 2022 Datacenter

Describe the Bug

Poison Wait alerts are firing repeatedly even though the actual wait time is 0ms, which is well below the configured threshold of 500ms avg wait.

Steps to Reproduce

1. Configure Poison Wait alert with threshold >= 500ms
2. Monitor a server where THREADPOOL (and other poison wait types) have 0ms avg wait
3. Alert fires repeatedly despite no actual poison waits occuring

Expected Behavior

No alert should fire when the avg wait time (0ms) is below the configured threshold (500ms)

Actual Behavior

Alert fires every ~5 minutes. The alert history log also records current_value: 0 and threshold_value: 0

Error Messages / Log Output

Screenshots

Additional Context

No response

[erikdarlingdata]

Root cause identified and fix submitted in PR #447.

Two bugs:

1. Stale data (root cause of false positives) — The Lite GetLatestPoisonWaitAvgsAsync query had no time filter (WHERE ... ORDER BY collection_time DESC LIMIT 3), so if a poison wait type had any activity days or weeks ago with AvgMsPerWait >= threshold, those old rows kept triggering the alert every 5 minutes indefinitely. Dashboard already had AND collection_time >= DATEADD(MINUTE, -10, SYSDATETIME()) — Lite was missing the equivalent. Fixed by adding AND collection_time >= NOW() - INTERVAL '10 minutes'.

2. Alert log showing 0/0 (misleading display) — The alert history logged current_value: 0 and threshold_value: 0 because EmailAlertService.LogAlertAsync tried double.TryParse on display strings like "THREADPOOL (523ms)" and "500ms avg", which fail to parse and default to 0. This made real alerts look like false positives at 0ms. Fixed by adding optional numeric parameters so call sites pass actual values for logging while keeping display strings for emails. This also affected LRQ, TempDB, and job alert log entries.