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https://issues.apache.org/jira/browse/LOG4J2-459?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Shaddy Baddah closed LOG4J2-459.
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Although I encountered LOG4J2-492 confirming the fix for this issue, I can
confirm that the fix works. Thanks :)
> Race condition on Web app configuration prevents ${web:initParam. lookup
> ------------------------------------------------------------------------
>
> Key: LOG4J2-459
> URL: https://issues.apache.org/jira/browse/LOG4J2-459
> Project: Log4j 2
> Issue Type: Bug
> Components: Core
> Affects Versions: 2.0-beta9
> Reporter: Shaddy Baddah
> Assignee: Ralph Goers
> Priority: Minor
> Fix For: 2.0-rc1
>
>
> I am happy for someone to challenge me on this assertion, but I cannot see
> how ${web:initParam.*} notation in XML configuration could ever work in
> 2.0-beta9 at least. Well at least for bootstrapped config.
> I have a Web application that includes an XML configfile in the WAR at:
> WEB-INF/classes/log4j2.xml
> The file looks something like this:
> ?xml version="1.0" encoding="UTF-8"?>
> <Configuration status="WARN">
> <Appenders>
> <File name="file" fileName="${web:initParam.myapp.logdir}/myapp.log"
> append="true">
> <PatternLayout pattern="%d [%t] %-5p %c - %m%n"/>
> </File>
> </Appenders>
> <Loggers>
> <Root level="warn">
> <AppenderRef ref="file"/>
> </Root>
> </Loggers>
> </Configuration>
> For the uninitiated, a recap on how ${web:initParam.myapp.logdir} is
> resolved, to the best of my understanding.
> The ${web: prefix will indicate to log4j2 that it should use the WebLookup
> class to resolve what comes after it; initParam.myapp.logdir.
> WebLookup will then check if that key is prefixed with initParam. (as well as
> another attr type prefix), and seeing that it is, will use the remainder as
> the real key name: myapp.logdir.
> It then calls getInitParameter() with that key on the ServletContext for the
> parent web application. That should pluck a value that could, for example, be
> configured in the web.xml like this:
> <context-param>
> <param-name>myapp.logdir</param-name>
> <param-value>c:/myapp_logs</param-value>
> </context-param>
> However, this is where there is a race condition. To get the ServletContext ,
> the WebLookup.lookup() method will call its own getServletContext() method.
> This in term attempt to get the ServletContext from the LogManager singleton,
> which stores it as an untyped (java.lang.Object) externalContext concept.
> For a Web App, this externalContext is not being set ahead of the
> bootstrapping parse of the XML config file.The problem can be seen in the
> sequencing of instructions in the Configurator.initialize() method:
> public static LoggerContext initialize(final String name, final
> ClassLoader loader, final URI configLocation,
> final Object externalContext) {
> try {
> final org.apache.logging.log4j.spi.LoggerContext context =
> LogManager.getContext(loader, false, configLocation);
> if (context instanceof LoggerContext) {
> final LoggerContext ctx = (LoggerContext) context;
> ContextAnchor.THREAD_CONTEXT.set(ctx);
> if (externalContext != null) {
> ctx.setExternalContext(externalContext);
> }
> This line:
> final org.apache.logging.log4j.spi.LoggerContext context =
> LogManager.getContext(loader, false, configLocation);
> kicks-off the boostrapped parse of the XML config, that in turn utilizes
> WebLookup.lookup().
> You can see however that ctx.setExternalContext(externalContext) is called
> after.
> Simple reasoning suggests that this initialization could be moved ahead.
> However this code applies to non-web apps too, and being not familiar with
> the design and intentions, I'd be very appreciative of someone looking into a
> fix for this.
> Thanks.
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