How to produce a header row in log4j2

Question

In log4j, we sometimes create a second logger and output CSV data to it as sort of a metrics watch of the application. This data is easily imported and graphed, as opposed to the normal log which we use for debugging and the like.

In old log4j we did this by subclassing the PatternLayout, overriding the header property, and specifying it as:

log4j.logger.servicePerformance=INFO, servicePerformance
log4j.appender.servicePerformance=mypackage.log4j.SingleHeaderFileAppender
log4j.appender.servicePerformance.File=logs/performance.log
log4j.appender.servicePerformance.layout=mypackage.log4j.HeaderLayout
log4j.appender.servicePerformance.layout.ConversionPattern=%m%n
log4j.appender.servicePerformance.layout.Header=Start Time, Service Invoked, Elapsed ms, Candidate Count, Asset Count
log4j.additivity.servicePerformance=false

I'm not sure how to do this in log4j 2 which we now have two applications recently converted to use.

Answer 1

Log4j2's PatternLayout also supports the header and footer attributes:

<PatternLayout>
  <pattern>%d %p [%t] %c %m%n</pattern>
  <header>This is a header</header>
  <footer>(c) 1999-2014</footer>
</PatternLayout>

I think attributes work too:

<PatternLayout pattern="%d %p [%t] %c %m%n"
  header="This is a header"
  footer="(c) 1999-2014" />

This is not documented correctly, thanks for pointing this out.