database-observability

Database Observability

Database is often the bottleneck. Track queries, pools, and patterns.

Query Span Attributes

Attribute	Example	Required
db.system	postgresql, mysql	Yes
db.operation	SELECT, INSERT	Yes
db.name	orders_db	Yes
db.sql.table	users	Recommended
db.statement	SELECT * FROM users WHERE id = ?	Parameterized only!

Connection Pool Metrics (USE)

Metric	Type	Description
db.connections.active	Gauge	In use
db.connections.idle	Gauge	Available
db.connections.max	Gauge	Pool limit
db.connections.wait_count	Counter	Had to wait
db.connections.wait_duration	Histogram	Wait time

Issues to Detect

Issue	Detection	Fix
N+1 queries	>10 identical queries per request	Use eager loading
Slow queries	Duration > p95 threshold	Add indexes, optimize
Pool exhaustion	wait_count increasing	Increase pool, fix leaks

Query Wrapper Pattern

Before: Start span (db.system, db.operation, db.sql.table), start timer
After:  Record duration, set db.rows_affected, record errors, end span

Pool Monitor Pattern

Every 10s: Record active, idle, wait_count, wait_duration from pool stats

Anti-Patterns

• Full SQL with values → PII risk, use parameterized only
• No pool metrics → Can't detect saturation
• Missing slow query alerts → Problems go unnoticed

References

• references/methodology/use-methodology.md
• references/platforms/{platform}/database.md