Spring Boot - PoolExhaustedException - spring

Question

I recently rebuild all my Spring 4 Projects with the latest Spring Boot Starter Framework.
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.7.RELEASE</version>
</parent>
Everything is working fine so far, except that i am experiencing PoolExhaustedException randomly across all my rebuild projects.
The exact exception is:
org.apache.tomcat.jdbc.pool.PoolExhaustedException: [http-nio-8080-exec-4] Timeout: Pool empty. Unable to fetch a connection in 20 seconds, none available[size:50; busy:50; idle:0; lastwait:20000].
The last exception i received was from a controller which is downloading a document from my database:
#RequestMapping(value = "/getDocument/{value}/{text}", method = RequestMethod.GET)
public void get(HttpServletResponse response, #PathVariable String value, #PathVariable String text){
try {
Document ufile = documentService.getDocumentByID(Integer.parseInt(value));
response.setContentType(ufile.getType());
response.setContentLength(ufile.getContent().length);
FileCopyUtils.copy(ufile.getContent(), response.getOutputStream());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Service:
#Transactional
public Document getDocumentByID(int id) {
Document r = this.documentDAO.getDocumentByID(id);
return r;
}
DAO:
#Transactional
public Document getDocumentByID(int id)
{
Session session = this.sessionFactory.getCurrentSession();
Document p = (Document) session.load(Document.class, new Integer(id));
return p;
}
I already tried to annotate the Controller with #Transactional which temporarily solved the problem, but led to other transactional errors so i had to remove it.
I also tried to increase the pool via project.properties too 100 which only delayed the problem but didn't solve it.
project.properties
spring.datasource.tomcat.max-wait=20000
spring.datasource.tomcat.max-active=50
spring.datasource.tomcat.max-idle=20
spring.datasource.tomcat.min-idle=15
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQLDialect
spring.jpa.properties.hibernate.id.new_generator_mappings = false
spring.jpa.properties.hibernate.format_sql = true
spring.mvc.view.prefix: /WEB-INF/views/
spring.mvc.view.suffix: .jsp
spring.jpa.properties.hibernate.current_session_context_class=org.springframework.orm.hibernate4.SpringSessionContext
spring.jpa.hibernate.naming.physical-strategy=org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl

Answer 1

Not sure if the properties with these names have any effect.
I'd also try to put a breakpoint and inspect the Tomcat DataSource directly to view the values to be convinced (can be easily autowired in a test).
Looking at the Spring Boot Tomcat Datasource Configuration Tests I see some interesting options like minEvictableIdleTimeMillis, timeBetweenEvictionRunsMillis and maxWait all prefixed with spring.datasource.tomcat., so give them a try.