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https://issues.apache.org/jira/browse/LOG4J2-169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13589399#comment-13589399
]
Noel Grandin commented on LOG4J2-169:
-------------------------------------
The thread-safe DCL looks like:
public static ConfigurationFactory getInstance() {
if (factories == null) {
synchronized (TEST_PREFIX) {
if (factories == null) {
List<ConfigurationFactory> list = new
ArrayList<ConfigurationFactory>();
....
factories = Collections.unmodifiableList(list);
}
}
}
return configFactory;
}
Otherwise, later on, someone adds something that shouldn't be executed more
than once inside the inner block, and bad stuff happens :-)
> 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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