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[BUG] Deadlock alerts re‑fire on the rolling 1‑hour count every cooldown #1091
Description
Component
Lite
Performance Monitor Version
2.11.0
SQL Server Version
Microsoft SQL Server 2022 (RTM-CU19) (KB5054531) - 16.0.4195.2 (X64)
Windows Version
Windows Sever 2019
Describe the Bug
It seems alerts deadlock alerts are generated without checking for new deadlocks but rather checking what's in the buffer for particular period.
Steps to Reproduce
I have caused two deadlock events, but you can see that each five minutes I am getting alert about it:
Expected Behavior
I would like to get alert only when new deadlock occurred. From what I checked, the full version already has this (at least the LLM says that):
The Dashboard edition already uses delta tracking (deadlockDelta = DeadlockCount − prevCount)
Actual Behavior
Each 5 minutes I am getting the same message:
Error Messages / Log Output
Screenshots
No response
Additional Context
I see there are some ways to stop this, but I believe it should be changed:
Activity
#1091: de-flap Dashboard "Deadlocks Cleared" to match Lite's window s…
Merge pull request #1097 from erikdarlingdata/feature/1091-alert-refi…
erikdarlingdata commentedon Jun 15, 2026
Fixed in #1097 — deadlock (and blocking) alerts now use an edge-trigger gate (
RollingCountAlertGate) with a per-server watermark, so they fire only on genuinely new events instead of re-firing on the rolling 1-hour count every cooldown.Because Lite's deadlock count is a rolling-window
COUNT(*)(it rises and falls), a naive delta wouldn't be safe — so the watermark decays as events age out of the window and resets below threshold, which also means a new event arriving during a cooldown won't be swallowed. Test-gated (RollingCountAlertGateTests).On
dev, ships next release. Closing.Fix erikdarlingdata#1091: edge-trigger Lite blocking/deadlock alerts …
Fix low-disk alert re-firing every cooldown for standing full volumes (…
Fix erikdarlingdata#1145: Webhook alerts re-fire after an app restart
Phase-5: Lite forwards to the shared alert engine
Address review: sentinel dedup reintroduced the #1091 re-fire class
Add Postgres Deadlocks and Blocking alerts (part of erikdarlingdata#2711