"Cannot get a connection" exception

[Luca Adamo]

Hi everyone,

I'm developing a web-application using the JSF framework and I'm deploying it on a Apache Tomcat 6.0.18. The server is installed on a CentOS5 Linux server.

Sometime, apparently without any reason I get the following exception:

org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot get a connection, pool error Timeout waiting for idle object

and the DB cannot be queried anymore (no more connections possible from my application). The only solutions is to restart Tomcat or the machine.


I'm handling user authentication through the Apache Tomcat DataSourceRealm method. My database is an Oracle XE and as a connector I'm using the one supplied by Oracle ojdbc14.jar.

I open connections to my DB with a JNDI Resource. The configuration (from context.xml) is the following one:

<Context antiJARLocking="true" path="/LampPost">
  <Realm className="org.apache.catalina.realm.JDBCRealm" connectionName="LAMP"
  connectionPassword="LAMP" connectionURL="jdbc:oracle:thin:@172.16.235.129:1521:xe"
  debug="99"
  driverName="oracle.jdbc.driver.OracleDriver" roleNameCol="ROLE"
  userCredCol="ANA_WEB_PASSWORD" userNameCol="ANA_WEB_USERNAME" userRoleTable="ROLES" userTable="ANAGRAFICA"/>

  <Resource driverClassName="oracle.jdbc.driver.OracleDriver" maxActive="20" maxIdle="10"
  maxWait="5000" name="jdbc/lamppost" password="LAMP" type="javax.sql.DataSource"
  url="jdbc:oracle:thin:@172.16.235.129:1521:xe" username="LAMP"/>
  </Context>

I'm closing every connection through a method that close every previously opened instance of the following classes: Connection, Statement, PreparedStatement, ResultSet. I tried also monitoring the number of connection opened at one time and they never overcome a total of 3.

The same happens with the Tomcat Server given in bundle with NetBeans 6.7.

Below a full stack-trace taken from the catalina.out log file.

   Sep 4, 2009 2:45:58 PM lamp.view.SystemBean recuperaUtente
SEVERE: null
lamp.exceptions.LampDBException: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot get a connection, pool error Timeout waiting for idle object
	at lamp.logic.Database.trovaGuastiPerStazioneEUtente(Database.java:2102)
	at lamp.logic.Database.modDatiCaricaStazioni(Database.java:1676)
	at lamp.logic.ModelloDati.caricaDati(ModelloDati.java:219)
	at lamp.logic.ModelloDati.init(ModelloDati.java:143)
	at lamp.logic.ModelloDati.<init>(ModelloDati.java:104)
	at lamp.view.SystemBean.recuperaUtente(SystemBean.java:67)
	at sun.reflect.GeneratedMethodAccessor26816.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.el.parser.AstValue.invoke(AstValue.java:172)
	at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:276)
	at org.apache.jasper.el.JspMethodExpression.invoke(JspMethodExpression.java:68)
	at org.ajax4jsf.component.AjaxViewRoot.processPhaseListeners(AjaxViewRoot.java:173)
	at org.ajax4jsf.component.AjaxViewRoot.processPhase(AjaxViewRoot.java:211)
	at org.ajax4jsf.component.AjaxViewRoot.processApplication(AjaxViewRoot.java:462)
	at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:97)
	at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:251)
	at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:117)
	at javax.faces.webapp.FacesServlet.service(FacesServlet.java:244)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:154)
	at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:260)
	at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:366)
	at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:493)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:525)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	at java.lang.Thread.run(Thread.java:619)
Caused by: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot get a connection, pool error Timeout waiting for idle object
	at org.apache.tomcat.dbcp.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:104)
	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
	at lamp.logic.Database.connetti(Database.java:1265)
	at lamp.logic.Database.trovaGuastiPerStazioneEUtente(Database.java:2061)
	... 37 more
Caused by: java.util.NoSuchElementException: Timeout waiting for idle object
	at org.apache.tomcat.dbcp.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:958)
	at org.apache.tomcat.dbcp.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:96)
	... 40 more
 

Thanks for any help

Luca

[Jan Cumps]

I'm closing every connection through a method that close every previously opened instance of the following classes: Connection, Statement, PreparedStatement, ResultSet. I tried also monitoring the number of connection opened at one time and they never overcome a total of 3.

Recheck that code. The error shows that you are out of connections. Better close Connection, Statement, etc... in the proper place: immediately after use, in a final block.

[Luca Adamo]

Jan Cumps wrote:

I'm closing every connection through a method that close every previously opened instance of the following classes: Connection, Statement, PreparedStatement, ResultSet. I tried also monitoring the number of connection opened at one time and they never overcome a total of 3.

Recheck that code. The error shows that you are out of connections. Better close Connection, Statement, etc... in the proper place: immediately after use, in a final block.

Actually I do close everything in the final block. I also tought that there must be an error somewhere, but I can't find it! :P so I was wondering if the reason could be different. I'll recheck my code. Thanks

[Jan Cumps]

Sagar Rohankar suggested to use the logAbandoned property to find leaks.
See this thread: http://www.coderanch.com/t/465105/JDBC/java/Inputs-needed-writing-tool-resolve

[Luca Adamo]

Jan Cumps wrote:Sagar Rohankar suggested to use the logAbandoned property to find leaks.
See this thread: http://www.coderanch.com/t/465105/JDBC/java/Inputs-needed-writing-tool-resolve

That seems quite interesting...i'll give a try...tahnks!

[Luca Adamo]

That logAbandoned property actually helped: I found the error; there was one, indeed. Thanks!