Deadlock during refresh properties

• Key: CONFIGURATION-344
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Critical
• Assignee: Oliver Heger
• Reporter: Pavel Savara
• Component/s: Events & Notifications, File reloading
• Affects Version/s: 1.5
• Fix Version/s: 1.6

Description

Hi
Commons configurations get itself stuck in deadlock when refreshing
properties using Managed reloading strategy. It seems to me it get stuck
because of fireEvent in reload method. Another access grabs lock on
synchronized (getNodeCombiner()) when trying to rebuild but Combined
configuration is one of the listeners for event es well and it gets
stuck when processing invalidate. Can anyone suggest quick fix please?
Relevant information follows.
Thanks
Pavel

Configuration:

<configuration> 
  <override>
    <system/>    
    <properties fileName="gsxweb.properties" throwExceptionOnMissing="false"
       config-name="gsxweb" config-optional="false" listDelimiter="|">
       <reloadingStrategy config-class="org.apache.commons.configuration.reloading.ManagedReloadingStrategy"/>      
    </properties>    
  </override> 
</configuration>

Our Reload code:

int ln = combinedConfiguration.getNumberOfConfigurations();
        int reloaded = 0;
        for (int i = 0; i < ln; i++) {
            Configuration conf = combinedConfiguration.getConfiguration(i);
            if (conf instanceof PropertiesConfiguration) {
                ManagedReloadingStrategy strat = null;
                ReloadingStrategy strategy = ((PropertiesConfiguration) conf).getReloadingStrategy();
                //refresh if managed strategy
                if (strategy instanceof ManagedReloadingStrategy) {
                    ((ManagedReloadingStrategy) strategy).refresh();
                //reload if file changed strategy    
                } else if (strategy instanceof FileChangedReloadingStrategy) {                    
                    ((PropertiesConfiguration) conf).reload();
                }
                reloaded++;
            }
        }

Stack trace of deadlock threads
Name: http-10980-1
State: BLOCKED on
org.apache.commons.configuration.tree.OverrideCombiner@8511bb owned by:
http-10980-6
Total blocked: 154  Total waited: 2

Stack trace: 
org.apache.commons.configuration.CombinedConfiguration.invalidate(CombinedConfiguration.java:474)
org.apache.commons.configuration.CombinedConfiguration.configurationChanged(CombinedConfiguration.java:488)
org.apache.commons.configuration.event.EventSource.fireEvent(EventSource.java:249)
org.apache.commons.configuration.AbstractFileConfiguration.fireEvent(AbstractFileConfiguration.java:911)
org.apache.commons.configuration.AbstractFileConfiguration.reload(AbstractFileConfiguration.java:828)
   - locked java.lang.Object@127e34c
org.apache.commons.configuration.AbstractFileConfiguration.isEmpty(AbstractFileConfiguration.java:927)
org.apache.commons.configuration.reloading.ManagedReloadingStrategy.refresh(ManagedReloadingStrategy.java:91)
com.gsx.properties.PropertyProviderImpl.reset(PropertyProviderImpl.java:203)
   - locked java.lang.Class@109bcda
org.apache.jsp.test.testPropertyProvider_jsp._jspService(testPropertyProvider_jsp.java:60)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)


Name: http-10980-6
State: BLOCKED on java.lang.Object@127e34c owned by: http-10980-1
Total blocked: 115  Total waited: 2

Stack trace: 
org.apache.commons.configuration.AbstractFileConfiguration.reload(AbstractFileConfiguration.java:814)
org.apache.commons.configuration.AbstractFileConfiguration.getKeys(AbstractFileConfiguration.java:939)
org.apache.commons.configuration.ConfigurationUtils.copy(ConfigurationUtils.java:139)
org.apache.commons.configuration.ConfigurationUtils.convertToHierarchical(ConfigurationUtils.java:199)
org.apache.commons.configuration.CombinedConfiguration
$ConfigData.getTransformedRoot(CombinedConfiguration.java:794)
org.apache.commons.configuration.CombinedConfiguration.constructCombinedNode(CombinedConfiguration.java:653)
org.apache.commons.configuration.CombinedConfiguration.getRootNode(CombinedConfiguration.java:504)
   - locked
org.apache.commons.configuration.tree.OverrideCombiner@8511bb
org.apache.commons.configuration.HierarchicalConfiguration.fetchNodeList(HierarchicalConfiguration.java:925)
org.apache.commons.configuration.HierarchicalConfiguration.getProperty(HierarchicalConfiguration.java:327)
org.apache.commons.configuration.CombinedConfiguration.getProperty(CombinedConfiguration.java:578)
org.apache.commons.configuration.AbstractConfiguration.resolveContainerStore(AbstractConfiguration.java:1155)
org.apache.commons.configuration.AbstractConfiguration.getString(AbstractConfiguration.java:1034)
org.apache.jsp.test.testPropertyProvider_jsp._jspService(testPropertyProvider_jsp.java:69)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)