Spring Hibernate SessionFactory performance issue

Spring boot app + Hikari + H2 Database to demonstrate Hibernate SessionFactory issue.

When the number of concurrent db requests is bigger than the configured maximumPoolSize(10 in this example) then the application becomes unresponsive.

In this example I created a single entity one Hibernate Dao with sessionFactory injected and one spring data repository.

Start DemoApplication and test with the following.

http://localhost:8080/stress-sessionfactory?threadsCount=11

(Stacktrace in the end)

On the other hand a Spring Data resository can easily manage thousands of concurrent requests wiht the same configuration Test it with http://localhost:8080/stress-jpa?threadsCount=2000

I Have tried the same scenario with different datasources(Hikari, Tomcat) , different databases(oracle,h2) and also with hibernate version v4.3.11-Final and I always get the same error.

StackTrace:

Exception in thread "Thread-51" Exception in thread "Thread-47" org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
	at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:431)
	at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:447)
	at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:277)
	at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:656)
	at com.example.dao.TypeDAOHibernate$$EnhancerBySpringCGLIB$$e6373e2e.findAll(<generated>)
	at com.example.controller.StressController.lambda$stressTest$0(StressController.java:36)
	at java.lang.Thread.run(Thread.java:745)
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1692)
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1602)
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:1700)
	at org.hibernate.jpa.internal.TransactionImpl.begin(TransactionImpl.java:48)
	at org.springframework.orm.jpa.vendor.HibernateJpaDialect.beginTransaction(HibernateJpaDialect.java:189)
	at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:380)
	... 9 more
Caused by: org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
	at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:48)
	at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
	at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:109)
	at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:95)
	at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.acquireConnectionIfNeeded(LogicalConnectionManagedImpl.java:90)
	at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.getPhysicalConnection(LogicalConnectionManagedImpl.java:112)
	at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.getConnectionForTransactionManagement(LogicalConnectionManagedImpl.java:230)
	at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.begin(LogicalConnectionManagedImpl.java:237)
	at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.begin(JdbcResourceLocalTransactionCoordinatorImpl.java:214)
	at org.hibernate.engine.transaction.internal.TransactionImpl.begin(TransactionImpl.java:52)
	at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1512)
	at org.hibernate.jpa.internal.TransactionImpl.begin(TransactionImpl.java:45)
	... 11 more
Caused by: java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30001ms.
	at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:591)
	at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:194)
	at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:146)
	at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112)
	at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:122)
	at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:386)
	at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.acquireConnectionIfNeeded(LogicalConnectionManagedImpl.java:87)
	... 18 more
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