HikariCP - connection is not available

I managed to fix it finally. The problem is not related to HikariCP.The problem persisted because of some complex methods in REST controllers executing multiple changes in DB through JPA repositories. For some reasons calls to these interfaces resulted in a growing number of "freezed" active connections, exhausting the pool. Either annotating these methods as @Transactional or enveloping all the logic in a single call to transactional service method seem to solve the problem.

From stack trace:

HikariPool: Timeout failure pool HikariPool-0 stats (total=20, active=20, idle=0, waiting=0)Means pool reached maximum connections limit set in configuration.

The next line:HikariPool-0 - Connection is not available, request timed out after 30000ms.Means pool waited 30000ms for free connection but your application not returned any connection meanwhile.

Mostly it is connection leak (connection is not closed after borrowing from pool),set leakDetectionThreshold to the maximum value that you expect SQL query would take to execute.

otherwise,your maximum connections 'at a time' requirement is higher than 20 !