WebappClassLoader clearReferencesThreads

[Leo Donahue - PLANDEVX <Le...@mail.maricopa.gov>]

This is really a two part question.

The first question has to do with the error in the log file and the second question has to do with making connections to other app servers in Tomcat.

Part 1:

I have a webapp (http://planning.maricopa.gov/apnxy) running under Tomcat 6.0.26 that makes a connection to a different app server that hosts the GIS part of the webapp.  That app server is always running, even when I shutdown Tomcat.

I looked at the source for WebappClassLoader: http://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk/java/org/apache/catalina/loader/
 and I see that Tomcat is trying to terminate the thread that the apnxy web app started.

I could stop the GIS service on the app server prior to restarting Tomcat, then start the app server.


Part 2:
What is the correct way to make connections to things that are not data sources in Tomcat?  Can Tomcat manage the connection information (machine name, domain, user, password)?  How?


Making a server connection to an ArcGIS Server app server:
http://resources.esri.com/help/9.3/arcgisserver/adf/java/help/api/arcobjects/com/esri/arcgis/server/ServerConnection.html

PDUManagerImpl: http://edndoc.esri.com/arcobjects/9.2/Java/api/arcobjects/com/esri/arcgis/interop/PDUManagerImpl.html

WebappClassLoader: http://tomcat.apache.org/tomcat-6.0-doc/api/org/apache/catalina/loader/WebappClassLoader.html


Catalina logs:

Jul 5, 2010 9:42:45 AM org.apache.coyote.http11.Http11AprProtocol pause
INFO: Pausing Coyote HTTP/1.1 on http-80
Jul 5, 2010 9:42:45 AM org.apache.coyote.ajp.AjpAprProtocol pause
INFO: Pausing Coyote AJP/1.3 on ajp-8009
Jul 5, 2010 9:42:46 AM org.apache.catalina.core.StandardService stop
INFO: Stopping service Catalina
Jul 5, 2010 9:42:47 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: A web application appears to have started a thread named [PDUManagerImpl-openConnection] but has failed to stop it. This is very likely to create a memory leak.
Jul 5, 2010 9:42:47 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: A web application appears to have started a thread named [PDUManagerImpl-openConnection] but has failed to stop it. This is very likely to create a memory leak.
Jul 5, 2010 9:42:47 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: A web application appears to have started a thread named [PDUManagerImpl-openConnection] but has failed to stop it. This is very likely to create a memory leak.
Jul 5, 2010 9:42:47 AM org.apache.coyote.http11.Http11AprProtocol destroy
INFO: Stopping Coyote HTTP/1.1 on http-80



Using CATALINA_BASE:   "C:\apache-tomcat-6.0.26"
Using CATALINA_HOME:   "C:\apache-tomcat-6.0.26"
Using CATALINA_TMPDIR: "C:\apache-tomcat-6.0.26\temp"
Using JRE_HOME:        "C:\Program Files\Java\jdk1.6.0_20"
Using CLASSPATH:       "C:\apache-tomcat-6.0.26\bin\bootstrap.jar"
Server version: Apache Tomcat/6.0.26
Server built:   March 9 2010 1805
Server number:  6.0.26.0
OS Name:        Windows 2003
OS Version:     5.2
Architecture:   x86
JVM Version:    1.6.0_20-b02
JVM Vendor:     Sun Microsystems Inc.

Leo Donahue

RE: WebappClassLoader clearReferencesThreads

["Caldarale, Charles R" <Ch...@unisys.com>]

> From: Leo Donahue - PLANDEVX [mailto:LeoDonahue@mail.maricopa.gov]
> Subject: WebappClassLoader clearReferencesThreads
> 
> I looked at the source for WebappClassLoader:
> http://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk/java/
> org/apache/catalina/loader/
> and I see that Tomcat is trying to terminate the thread 
> that the apnxy web app started.

Which means Tomcat is trying to recover from sloppy programming in the webapp.  It's the webapp's responsibility to manage all threads it creates, including terminating them when the webapp is stopped.

> What is the correct way to make connections to things that 
> are not data sources in Tomcat?  Can Tomcat manage the 
> connection information (machine name, domain, user, password)?

No, Tomcat cannot do that - there's nothing in the servlet spec that provides for that.  (But check the 3.0 spec and Tomcat 7 - I haven't studied them yet.)  It's up to the webapp to deal with outbound connections, and manage them properly to avoid resource leaks.  Various 3rd-party libraries are available to help with that.

 - Chuck


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Re: WebappClassLoader clearReferencesThreads

[Konstantin Kolinko <kn...@gmail.com>]

2010/7/6 Leo Donahue - PLANDEVX <Le...@mail.maricopa.gov>:
> Part 2:
> What is the correct way to make connections to things that are not data sources in Tomcat?  Can Tomcat manage the connection information (machine name, domain, user, password)?  How?
>

There is JNDI support available, so that you can declare <Resource> if
you provide an appropriate factory="" for it.

http://tomcat.apache.org/tomcat-6.0-doc/jndi-resources-howto.html

The factories are provided for some standard resource types (like
java.sql.DataSource).

Actually, Tomcat does not implement that factory by itself, but uses
Apache Commons DBCP library from http://commons.apache.org/ which
itself is based on Apache Commons Pool library.

Best regards,
Konstantin Kolinko

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