org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection - spring-boot

Question

I sometimes notice below mentioned error in my springboot app logs.
org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
I suspect it could be because of exception thrown from #Transactional method ( only at times though).
Is it Ok to throw excaption from #Transactional method? or it is a bad practice?
Here is my service layer code
#Override
#Transactional
public void updateMessageStatus(String status, String sid, String errorCode) throws NotFoundException {
OutgoingMessage outgoingMessage = outgoingMessageRepository.findByResourceSid(sid);
if (outgoingMessage == null) {
throw new NotFoundException(ErrorCode.MESSAGE_NOT_FOUND, sid);
}
outgoingMessage.setStatus(status);
outgoingMessage.setUpdatedTime(Calendar.getInstance().getTime());
outgoingMessageRepository.save(outgoingMessage);
}

Answer 1

This usually happens when app is idle for longer time than the server’s connection timeout period.
So if a connection has been idle longer than this timeout value, it will be dropped by the server. By default, Hibernate uses its internal database connection pool library,
keeping the connection open to be reused later.
Hibernate reuses the idle connection which was already dropped by the server, hence we get JDBCConnectionExceptionis error.
What I noticed is even with the following database auto-reconnect setup should not work in this case.
spring.datasource.validation-query=select 1
spring.datasource.testOnBorrow=true
May be need to increase the pool size OR Entity Manager needs to be closed once the transaction is done.
spring.datasource.hikari.maximum-pool-size=10.
Please let me know if this worked for you.