We recently evaluated JDBC connections pools for Java SE and were impressed by the connection validation algorithm implemented by HikariCP. We would like to see something similar implemented by Agroal.

HikariCP implements validate-on-borrow using java.sql.Connection.isValid(int) (Java 1.6/JDBC 4.0). However if the connection has been successfully used in the past 500ms then this check is bypassed. To quote the author

Generally speaking, in an active application or process, this avoids nearly all validation, while providing confidence that the connections returned by the pool are actually alive.

Discussion is here https://groups.google.com/forum/#!searchin/hikari-cp/batch%7Csort:date/hikari-cp/6XOI8_x9YeU/G3k6g9otAAAJ