You are most likely having this problem because when you create your uber jar
you can only include one of the Log4j2Plugins.dat files. Both the log4j2-core
jar and the log4j2-flume jar are going to have one. This has been discussed in
https://issues.apache.org/jira/browse/LOG4J2-1059
<https://issues.apache.org/jira/browse/LOG4J2-1059> (which probably can be
closed), https://issues.apache.org/jira/browse/LOG4J2-369
<https://issues.apache.org/jira/browse/LOG4J2-369>, and
https://issues.apache.org/jira/browse/LOG4J2-673
<https://issues.apache.org/jira/browse/LOG4J2-673>. This last one has a
solution in the middle of the discussion by way of a Transformer that can be
used in the maven shade plugin. However, you are using the assembly plugin, so
I am not really sure how you can do it that way.
Ralph
> On May 4, 2016, at 12:43 PM, Julian Keppel <juliankeppel1...@gmail.com> wrote:
>
> Hi everyone,
>
> I tested the flume appender for log4j2. My configuration XML looks like
> this:
>
> <Configuration status="ERROR" name="some_name">
>
> ...
>
> <Appenders>
>
> ...
>
> <Flume name="FLUME" compress="true">
> <Agent host="${FLUME_HOST}" port="${FLUME_PORT}"/>
> <PatternLayout pattern="${LOG_PATTERN}"/>
> <ThresholdFilter level="INFO" onMatch="ACCEPT" onMismatch="DENY"/>
> </Flume>
> </Appenders>
>
> <Loggers>
> <Root level="DEBUG">
> <AppenderRef ref="FLUME"/>
> ...
> </Root>
> </Loggers>
> </Configuration>
>
> And I build my application with maven assembly plugin to get an uber jar
> which contains all dependencies (I want to ship a single jar file to all
> the destination runtime environments).
>
> When I start the application I get the following error:
> ERROR Error processing element Flume ([Appenders: null]): CLASS_NOT_FOUND
>
> So it looks like there is some dependency missing. But in the official doc
> I read that for remote mode of the flume appender I only need the following
> dependency (including the necessary log4j dependencies):
>
> <dependencies>
>
> ...
>
> <dependency>
> <groupId>org.apache.logging.log4j</groupId>
> <artifactId>log4j-core</artifactId>
> <version>2.5</version>
> </dependency>
> <dependency>
> <groupId>org.apache.logging.log4j</groupId>
> <artifactId>log4j-api</artifactId>
> <version>2.5</version>
> </dependency>
> <dependency>
> <groupId>org.apache.logging.log4j</groupId>
> <artifactId>*log4j-flume-ng*</artifactId>
> <version>2.5</version>
> </dependency>
> </dependencies>
>
> Another hint: When I start the application from eclipse, it seems to work
> totally fine (at least I don't get the error from above).
>
> So what I am doing wrong here? Has anyone some advice for me? Thanks in
> advance.
>
> Julian
