[jira] [Updated] (LOG4J2-745) Plugins can cause ConverterKeys collisions with unpredictable results

["Matt Sicker (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LOG4J2-745?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Matt Sicker updated LOG4J2-745:
-------------------------------

    Attachment: LinkedHashMap_Plugin_Manager.patch

Here's a work in progress toward addressing the LinkedHashMap issue you mentioned. Note that I don't have JDK 1.6 on this computer, so I wasn't able to test whether or not this still compiles properly as JDK 1.8 added a ton of default interface methods.

> 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_Plugin_Manager.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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