Scott Harrington created LOG4J2-745:
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Summary: 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
Priority: Minor
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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