Scala Log4j configuration

Question

So I'm trying to set up log4j in my scala code. This is what I have so far:

LogHelper.scala

package myPackage

import org.apache.log4j.Logger

trait LogHelper {
    val loggerName: String = this.getClass.getName
    lazy val logger: Logger = Logger.getLogger(loggerName)
}

my class

package myPackage

class MyClass extends LogHelper {

    ...
    logger.debug("my message")
    ...

}

But I don't really know where the logs go, or how to make it print to a file. My code is running a spark job which I run with spark-submit. How do I set this up to print to both the console and a log file?

Answer 1

Refer to this post. They have precise steps to get logging in Scala.

http://discuss.itversity.com/t/setting-up-log4j/5839:

Step 1: Update build.sbt with below log4j dependency

libraryDependencies += "log4j" % "log4j" % "1.2.14"

step 2: create Log4j.properties file under src/main/resources and update as follows:

# Define the root logger with appender file
log = /tmp/log4j
log4j.rootLogger = DEBUG, FILE

# Define the file appender
log4j.appender.FILE=org.apache.log4j.FileAppender
log4j.appender.FILE.File=${log}/log.out

# Define the layout for file appender
log4j.appender.FILE.layout=org.apache.log4j.PatternLayout
log4j.appender.FILE.layout.conversionPattern=%m%n
SBT run, can be seen in /tmp/log4j/log.out log

Step 3: Can be used in code as follows:

import org.apache.log4j.Logger

object HelloWorld {
  val logger = Logger.getLogger(this.getClass.getName)
  def main(args: Array[String]): Unit = {
    logger.info("Logger : Welcome to log4j")
  }
}

If you wanna know more about logging with log4j, I recommend this post on DZone:

https://dzone.com/articles/logging-with-log4j-in-java