JDBC connection pool - muhamed-hassan/safe_planet GitHub Wiki

A connection pool is a cache of reusable database connections managed by the application server. It reduces the overhead of opening and closing connections, improving performance and scalability in database applications.

Relational databases typically use stateful, binary protocols that maintain session-specific information, such as transaction states and prepared statements, necessitating optimized connection pooling to minimize the overhead of repeatedly establishing connections.

Connection Limits and overprovisioning:

In database environments, connection limits are typically determined by configurations. Some database enforces limits based on allocated resources, such as CPU, memory, ..., etc. When connection pool configurations exceed these limits, issues such as rejected connections, throttling, or degraded performance can occur.

Depending on how database limits are applied, overprovisioned connection pools can create significant resource contention as the server struggles to manage excessive simultaneous connections. Idle connections may encounter issues due to network conditions, such as NAT timeouts or dropped connections, or database state changes, such as session invalidation or transaction timeouts, potentially triggering reconnection processes that introduce additional overhead and performance penalties. Over-provisioned pools can overwhelm server resources, causing increased latency and degraded system performance. To optimize database connectivity, connection pool configurations should be carefully aligned with the database's capacity and the application's specific workload, ensuring efficient connection reuse without overburdening the database server and maintaining a balance between connection availability and resource utilization.