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From "Kenneth Xu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (BEANUTILS-49) [beanutils] Lock in BeanUtilsBean.getInstance(BeanUtilsBean.java:78)
Date Wed, 08 Nov 2006 04:42:54 GMT
    [ http://issues.apache.org/jira/browse/BEANUTILS-49?page=comments#action_12448029 ] 
            
Kenneth Xu commented on BEANUTILS-49:
-------------------------------------

There is no doubt that Struts code should be changed to make best use of beanutils. But I
believe there is still some space for beanutils to improve too.

I think the getInstance is unnecessarily synchronized as the beansByClassLoader.get is already
synchronized. Futher, synchronize the entire beansByClassLoader.get method seems to be overkill.
As there is so much existing code written to use the static methods in BeanUtils class, it's
very likely that the getInstance becomes hotspot in an heavy loaded application. So developers
would love to see every bit of performance gain in the getInstance call.

> [beanutils] Lock in BeanUtilsBean.getInstance(BeanUtilsBean.java:78)
> --------------------------------------------------------------------
>
>                 Key: BEANUTILS-49
>                 URL: http://issues.apache.org/jira/browse/BEANUTILS-49
>             Project: Commons BeanUtils
>          Issue Type: Bug
>          Components: Bean / Property Utils
>         Environment: Operating System: other
> Platform: Other
>            Reporter: Jesper Richter-Reichhelm
>         Assigned To: Niall Pemberton
>
> Commons Beanutils 1.7 introduced a new problem:
> During high traffic times threads begin to wait at the synchronized method
> org.apache.commons.beanutils.BeanUtilsBean.getInstance() which causes the
> complete thread pool to be used up in our Struts 1.2.7 based web application. In
> our live environment this caused all 70 threads to be blocked by the same lock.
> This behaviour can be easily reproduced by a calling a 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).
> <!-- 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 1.2.7 and Commons Beanutls 1.7.0 reproduces the lock (in
> this example with 10 concurrent threads):
> 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.java:78)
>         - waiting to lock <0x6c86eab0> (a java.lang.Class)
>         at
> org.apache.commons.beanutils.PropertyUtilsBean.getInstance(PropertyUtilsBean.java:101)
>         at
> org.apache.commons.beanutils.PropertyUtils.getProperty(PropertyUtils.java: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)
> ...
> This behaviour is new to version 1.7. The same test using Commons Beanutils
> 1.6.1 showed no problems: By falling back to the old version we could
> temporarily solve our live problems and could continue to use Struts 1.2.7.
> Nevertheless this should be fixed.

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