What Is Connection Pool Exhaustion?

Connection pool exhaustion is the state in which every connection in a fixed-size pool is checked out and busy, leaving no free connection for an incoming request. The request then blocks until one is released or fails when a wait timeout is reached. It usually stems from connections held too long, leaked, or a pool sized below demand.

Why it matters

Integration tests in CI that open many parallel database or HTTP calls can drain a pool and fail with timeout errors that look like the service is down. Recognizing exhaustion points to releasing connections promptly or sizing the pool correctly.

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