Database connection pool exhausted
Concurrent test work requested more database connections than the configured pool could provide before its timeout.
RECOGNIZABLE ERROR
Timed out fetching a new connection from the connection poolRANKED DIAGNOSIS
What usually causes it
- 01
Each test creates a new client
Clients are opened repeatedly and not reused or closed.
DIAGNOSE
Count client construction and active connections per worker.
FIX
Create one lifecycle-managed client per worker and close it after the suite.
- 02
Worker concurrency exceeds the database budget
Parallel processes multiply each client's pool size.
DIAGNOSE
Calculate workers multiplied by pool maximum and compare it with the server limit.
FIX
Reduce per-worker pool size or test concurrency while preserving isolation.
- 03
Transactions or streams leak connections
An error path may skip release or rollback.
DIAGNOSE
Inspect long-running sessions and unclosed transaction paths.
FIX
Use scoped helpers that release in finally blocks.
Prevent the repeat
- →Budget connections across workers.
- →Manage clients at worker scope.
- →Assert cleanup on failure paths.
Primary references
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