At a customer whose repository sits on a monitored instance, the agent
reported 12 deadlocks that were its own: two instances' monitors save
findings in parallel, one transaction each, and while insight.Findings is
small SQL Server scans it, so the two lock each other's rows.
- SaveRuleResultsAsync takes an exclusive application lock for its
transaction (the agent is the only writer; a save takes milliseconds)
and retries if chosen as deadlock victim anyway
- repository connections are named "SQLInsight Pro (repository)"
- deadlocks where every participant is SQLInsight Pro are not reported
(the read position still moves past them); any other session keeps it
The new integration test (two instances saving 25 rules x 40 rounds in
parallel) failed 2 of 2 without the fix and passed 5 of 5 with it.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Collectors (SQL Server 2000+, version-specific SQL, least privilege):
server, configuration, trace flags, databases (settings, backups in UTC,
CHECKDB, VLFs, Query Store, files, tempdb), suspect pages, plan cache,
wait stats and file I/O as deltas with restart/clear detection,
performance counters, CPU from the scheduler monitor ring buffer,
blocking (sleeping head blockers with open transactions), and deadlocks
from system_health continuing from the last file offset.
Rules: configuration (memory, MAXDOP per Microsoft NUMA guidance, cost
threshold, ad hoc bloat, risky options, pending changes), databases
(state, settings, backups, log backups, CHECKDB, suspect pages, VLFs,
autogrowth, max size, Query Store, tempdb), waits (THREADPOOL, signal
waits, locks, I/O, WRITELOG, parallelism, PAGELATCH), I/O latency, CPU,
memory grants, blocking and deadlocks. Missing data makes a rule not
measurable with the collector's reason.
Integration tests run every collector as the least-privilege login and
reproduce real blocking and a real deadlock; green on 2017 and 2022.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E3EExwndy8Z22EK2Qpt6BK
