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Posted to log4j-dev@logging.apache.org by "Remko Popma (JIRA)" <ji...@apache.org> on 2014/07/28 05:56:38 UTC
[jira] [Comment Edited] (LOG4J2-745) Plugins can cause
ConverterKeys collisions with unpredictable results
[ https://issues.apache.org/jira/browse/LOG4J2-745?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14075876#comment-14075876 ]
Remko Popma edited comment on LOG4J2-745 at 7/28/14 3:55 AM:
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I think all we need to do is detect a collision and warn the user. It would be nice if we could say plug-in X uses the same conversion pattern so plug-in Y is being ignored (so the use knows which plugin is ignored in this particular case). Just a warning without making any guarantees about who wins is good enough I think.
was (Author: remkop@yahoo.com):
I think all we need to do is detect a collision and warn the user. It would be nice if we could say plug-in X uses the same conversion pattern so plug-in Y is being ignored. Just a warning without making any guarantees about who wins is good enough I think.
> Plugins can cause ConverterKeys collisions with unpredictable results
> ---------------------------------------------------------------------
>
> Key: LOG4J2-745
> URL: https://issues.apache.org/jira/browse/LOG4J2-745
> Project: Log4j 2
> Issue Type: Improvement
> Reporter: Scott Harrington
> Assignee: Matt Sicker
> Priority: Minor
> Attachments: LinkedHashMap_and_locks.patch
>
>
> If I create a Converter plugin with ConverterKeys of "d" or "m" then there will be a collision with the built-in DatePatternConverter or MessagePatternConverter.
> It is unpredictable which plugin gets used.
> I see two resolutions:
> (1) detect collisions in PatternParser and emit a warning so we know which implementation will be used
> (2) use whichever Log4j2Plugins.dat appeared first in the CLASSPATH
> Predictable iteration order is usually accomplished by replacing HashMaps with LinkedHashMaps. Could easily do this for thie PluginManager.plugins field. But PluginRegistry uses a ConcurrentHashMap.
> Is there a good reason to use ConcurrentHashMaps in PluginRegistry? It doesn't really give you any concurrency -- a caller to PluginManager.getPlugins could see a partially-loaded map if collectPlugins was still running. Why not synchronize collectPlugins and/or loadPlugins, and force any concurrent caller to getPlugins to wait until the loading was complete.
> I would give it a stab but I see other more important changes are probably underway for LOG4J2-741 and LOG4J2-673 and this can probably wait.
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