Lock in BeanUtilsBean.getInstance(BeanUtilsBean.java:78)

["Richter-Reichhelm, Jesper" <je...@jamba.net>]

After switching to Struts 1.2.7 (and Commons Beanutils 1.7) we
experience problems with Struts Tags' usage of
PropertyUtils.getProperty() to read a bean's property value: During high
traffic time threads begin to wait at the synchronized method
org.apache.commons.beanutils.BeanUtilsBean.getInstance() which causes
the complete Thread pool to be used up (all 70 threads in our live
configuration).

The locked threads all look like this:
"ExecuteThread: '16' for queue: 'weblogic.kernel.Default'" daemon prio=5
tid=0x013cc9b8 nid=0x1c waiting for monitor entry [8fb7e000..8fb7fc28]
        at
org.apache.commons.beanutils.BeanUtilsBean.getInstance(BeanUtilsBean.jav
a:78)
        - waiting to lock <0xf67320c0> (a java.lang.Class)
        at
org.apache.commons.beanutils.PropertyUtilsBean.getInstance(PropertyUtils
Bean.java:101)
        at
org.apache.commons.beanutils.PropertyUtils.getProperty(PropertyUtils.jav
a:290)
        at
org.apache.struts.taglib.logic.CompareTagBase.condition(CompareTagBase.j
ava:183)
        at
org.apache.struts.taglib.logic.EqualTag.condition(EqualTag.java:46)
        at
org.apache.struts.taglib.logic.ConditionalTagBase.doStartTag(Conditional
TagBase.java:174)
        at
jsp_servlet._sounds._ringtones.__index._jspService(__index.java:7826)
In the above example the EqualTag is calling PropertyUtils but this
happens with all Struts tags that need to read a bean's property value.

This behaviour can be easily reproduced by a calling the test JSP
provided below with multiple threads. Using the tool siege to
concurrently call the JSP with two threads is enough to reproduce the
lock scenario, the situation gets worse the more concurrent threads are
used (i.e. the throughput decreases).

Although the problem seems to have been caused by Commons Beanutils I
write to this mail group as this problem is new to Struts 1.2.7 - and we
were not able to reproduce the problem with Struts 1.1: In 1.1 the test
jsp's performance did not degrade by using more concurrent threads but
keeps stable - and no locks were visisble in the thread dumps. That's no
surprise because the classes PropertyUtilsBean and BeanUtilsBean were
not uses in Struts 1.1 / the old Commons Beanutils version.


Does anyone else have this problem? Is there a workaround or bugfix
available?

Thanks in advance.
Jesper Richter-Reichhelm



PS:

The test JSP:
<!-- begin of test JSP -->
<%@ taglib uri="/struts-logic.tld" prefix="logic" %>
<%@ taglib uri="/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/struts-tiles.tld" prefix="tiles" %>
<%@ taglib uri="/struts-html.tld" prefix="html" %>
<%@ taglib uri="/JLog.tld" prefix="jlog" %>

<%@ page import="java.util.*"%>
<%
   final long t0 = System.currentTimeMillis();
 Collection col = new ArrayList();
     for(int i = 0; i<5; i++)
     {
      org.apache.struts.util.LabelValueBean lvb = new
org.apache.struts.util.LabelValueBean("col"+i, "col"+i);
      col.add(lvb);
     }
   pageContext.setAttribute("col", col);
%>
<logic:notEmpty name="col"><logic:iterate name="col"
id="test"><logic:iterate name="col" id="test2"><logic:iterate name="col"
id="test3"><logic:iterate name="col" id="test3"><logic:iterate
name="col" id="test4"><logic:iterate name="col" id="test4">
<bean:define id="foo" name="test4" property="value"/><bean:define
id="bar" name="test4" property="label"/>
</logic:iterate></logic:iterate></logic:iterate></logic:iterate></logic:
iterate></logic:iterate></logic:notEmpty>
Finished!
<!-- end of test JSP --> 


A test run with Struts 1.1:
siege -c10 -r20 "localhost:1701/dcw/test.jsp"
=> There are no locks in the the thread dumps visible.


A test run with Struts 1.2.7:
siege -c10 -r20 "localhost:1701/dcw/test.jsp"
=> Thread dump is full with threads like this:
"ExecuteThread: '4' for queue: 'weblogic.kernel.Default'" daemon prio=1
tid=0x083859f8 nid=0x76f4 waiting for monitor entry [7628c000..7628c8bc]
        at
org.apache.commons.beanutils.BeanUtilsBean.getInstance(BeanUtilsBean.jav
a:78)
        - waiting to lock <0x6c86eab0> (a java.lang.Class)
        at
org.apache.commons.beanutils.PropertyUtilsBean.getInstance(PropertyUtils
Bean.java:101)
        at
org.apache.commons.beanutils.PropertyUtils.getProperty(PropertyUtils.jav
a:290)
        at org.apache.struts.taglib.TagUtils.lookup(TagUtils.java:950)
        at
org.apache.struts.taglib.bean.DefineTag.doEndTag(DefineTag.java:230)
        at jsp_servlet.__test._jspService(__test.java:309)
...

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