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From "Remko Popma (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (LOG4J2-169) LogManager.getLogger doesn't work
Date Sun, 03 Mar 2013 02:01:13 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13591576#comment-13591576
] 

Remko Popma edited comment on LOG4J2-169 at 3/3/13 2:00 AM:
------------------------------------------------------------

You are right, I missed the "volatile" declaration.

Still, the "static singleton" solution proposed in both the articles (in yours it's under
"Making it work for static singletons") looks a lot simpler:
(and it will be faster because it doesn't even have the volatile memory barrier).

private static List<ConfigurationFactory> factories = createFactories(); // no need
to make this volatile

public static List<ConfigurationFactory> getInstance() { return factories; } 

private static List<ConfigurationFactory> createFactories() { // no need for null checking
or synchronization here
    List<ConfigurationFactory> list = new ArrayList<ConfigurationFactory>();
     ....
    return Collections.unmodifiableList(list);
}

                
      was (Author: remkop@yahoo.com):
    You are right, I missed the "volatile" declaration.

Still, the "static singleton" solution proposed in both the articles (in yours it's under
"Making it work for static singletons") looks a lot simpler:
(and it will be faster because it doesn't even have the volatile memory barrier).

private static List<ConfigurationFactory> factories = createFactories(); // no need
to make this volatile

public static List<ConfigurationFactory> getInstance() { return factories; } // first
time this is called, the "factories" field is initialized

private static List<ConfigurationFactory> createFactories() { // no need for null checking
or synchronization here
    List<ConfigurationFactory> list = new ArrayList<ConfigurationFactory>();
     ....
    return Collections.unmodifiableList(list);
}

                  
> LogManager.getLogger doesn't work
> ---------------------------------
>
>                 Key: LOG4J2-169
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-169
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 2.0-beta4
>            Reporter: Jed Wesley-Smith
>            Priority: Critical
>              Labels: thread-safety
>
> We randomly get the following:
> java.util.ConcurrentModificationException
> 	at org.apache.logging.log4j.core.config.ConfigurationFactory$Factory.getConfiguration(ConfigurationFactory.java:377)
> 	at org.apache.logging.log4j.core.config.ConfigurationFactory$Factory.getConfiguration(ConfigurationFactory.java:361)
> 	at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:266)
> 	at org.apache.logging.log4j.core.LoggerContext.start(LoggerContext.java:134)
> 	at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:75)
> 	at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:30)
> 	at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:165)
> 	at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:174)
> 	at …
> factories is defined as:
>     private static List<ConfigurationFactory> factories = new ArrayList<ConfigurationFactory>();
> The simple fix is to use a java.util.concurrent.CopyOnWriteArrayList:
>     private static final List<ConfigurationFactory> factories = new CopyOnWriteArrayList<ConfigurationFactory>();
> https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk/core/src/main/java/org/apache/logging/log4j/core/config/ConfigurationFactory.java

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