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https://issues.apache.org/jira/browse/LOG4J2-3040?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17505332#comment-17505332
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ASF subversion and git services commented on LOG4J2-3040:
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Commit 9d3f8364161cdbdea6ee41ba810b505c4a217b1a in logging-log4j2's branch
refs/heads/dependabot/maven/org.apache.maven.plugins-maven-scm-plugin-1.12.2
from Gary Gregory
[ https://gitbox.apache.org/repos/asf?p=logging-log4j2.git;h=9d3f836 ]
[LOG4J2-3040] Avoid ClassCastException in JeroMqManager with custom
LoggerContextFactory #791
> ShutdownCallbackRegistry should be part of log4j-api, not log4j-core
> --------------------------------------------------------------------
>
> Key: LOG4J2-3040
> URL: https://issues.apache.org/jira/browse/LOG4J2-3040
> Project: Log4j 2
> Issue Type: Bug
> Reporter: Grzegorz Grzybek
> Priority: Major
>
> I'm working on https://github.com/ops4j/org.ops4j.pax.logging/issues/395
> related to Pax Logging project, which implements OSGi Log specification based
> on 3 _backends_:
> * Log4j1
> * Logback
> * Log4j2
> and several _frontends_:
> * Commons Logging
> * JULI Logging
> * javax.logging
> * SLF4J
> * Avalong
> * Log4j1 (API)
> * Log4j2 (API)
> * JBoss Logging
> Pax Logging implements own
> {{org.apache.logging.log4j.spi.LoggerContextFactory}}, where the
> {{org.apache.logging.log4j.spi.LoggerContext}} returned is managed by OSGi
> runtime (without using
> {{org.apache.logging.log4j.core.selector.ContextSelector}}).
> The problem is that several libraries assume that some casts are possible.
> There was an elasticsearch problem described
> [here|https://groups.google.com/g/ops4j/c/yjqOzvrKRkc/m/DZeUSdZeCAAJ], where
> level was set through configuration and
> {{org.apache.logging.log4j.core.LoggerContext#getContext(boolean)}}
> explicitly calls (in
> {{org.apache.logging.log4j.core.config.Configurator#setLevel()}}):
> {code:java}
> public static LoggerContext getContext(final boolean currentContext) {
> return (org.apache.logging.log4j.core.LoggerContext)
> LogManager.getContext(currentContext);
> }
> {code}
> assuming that {{org.apache.logging.log4j.LogManager#getContext(boolean)}}
> returns log4j-core specific implementation of the context.
> With https://github.com/ops4j/org.ops4j.pax.logging/issues/395 there's
> different problem.
> {{org.apache.logging.log4j.core.appender.mom.jeromq.JeroMqAppender}} (part of
> log4j-core library) [long time
> ago|https://github.com/apache/logging-log4j2/commit/a6af67c5d6faee5b4d422add674e4c518c33d528]
> started to use
> {{org.apache.logging.log4j.core.util.ShutdownCallbackRegistry}} for cleanup.
> Now this is moved to
> {{org.apache.logging.log4j.core.appender.mom.jeromq.JeroMqManager}}, but
> still there's this explicit code:
> {code:xml}
> if (enableShutdownHook) {
> SHUTDOWN_HOOK = ((ShutdownCallbackRegistry)
> LogManager.getFactory()).addShutdownCallback(CONTEXT::close);
> {code}
> While normally, LogManager.getFactor() returns an instance of
> {{org.apache.logging.log4j.core.impl.Log4jContextFactory}}, it's *not*
> guaranteed by {{org.apache.logging.log4j.LogManager#getFactory}} API and
> indeed - pax-logging-api's implementation returns a factory that doesn't
> implement {{ShutdownCallbackRegistry}}.
> I tried two approaches:
> # _move_ (in OSGi terms) some packages from log4j-core to pax-logging-api
> (for now, pax-logging-api only operates on log4j-api), howver, transitively I
> ended up with almost entire log4j-core inside pax-logging-api
> # refactor log4j2 itself (locally) so {{ShutdownCallbackRegistry}} (and
> {{Cancellable}}) are part of {{org.apache.logging.log4j.spi}} package, but I
> ended with quite long list of errors from
> org.revapi:revapi-maven-plugin:0.11.1:check
> Mind that even
> {{org.apache.logging.log4j.core.LoggerContext#setUpShutdownHook()}} correctly
> checks for the interface to be implemented:
> {code:java}
> final LoggerContextFactory factory = LogManager.getFactory();
> if (factory instanceof ShutdownCallbackRegistry) {
> {code}
> It's *only* org.apache.logging.log4j.core.appender.mom.jeromq.JeroMqManager
> that blindly calls:
> {code:java}
> SHUTDOWN_HOOK = ((ShutdownCallbackRegistry)
> LogManager.getFactory()).addShutdownCallback(CONTEXT::close);
> {code}
> Summarizing - ideally (IMO) {{ShutdownCallbackRegistry}} should be part of
> the API, but if it's not possible, please fix {{JeroMqManager}} to check for
> the implementation.
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