Configuring logback to write to different logs files

Question

I've an actor system with multiple actors. Actors are grouped by a fixed set of domains. Currently I'm logging to just one big log file which interleaves the logs from different actors belonging to different domains.

How can I configure logback so that each actor writes to its own .log file. Also, does writing to different log files compared to writing to a single one have a performance impact ?

Answer 1

What you require here is a SiftingAppender with a Actor/Actor system based discriminator.
Give the following configuration in your logback.xml

<appender name="SIFT" class="ch.qos.logback.classic.sift.SiftingAppender">
<discriminator class="com.abc.ActorDomainBasedDiscriminator"/>
<sift>
    <appender name="FILE-${actorDomain}" class="ch.qos.logback.core.rolling.RollingFileAppender">
 <file>app-${actorDomain}.log</file>
...

This configuration will result in log files being created like 'app-Domain1.log', 'app-Domain2.log' etc...

Define a class ActorDomainBasedDiscriminator

import ch.qos.logback.classic.spi.LoggingEvent
import ch.qos.logback.core.sift.Discriminator
import ch.qos.logback.core.spi.ContextAwareBase

class ActorDomainBasedDiscriminator extends ContextAwareBase with Discriminator[LoggingEvent] {
  private val Key = "actorDomain";

  @volatile
  private var started = false;

  def getDiscriminatingValue(event: LoggingEvent) = {
    val loggerName = event.getLoggerName
    if(loggerName.startsWith("Domain"))
      loggerName
    else event.getLevel.toString
  }

 def getKey: String = Key

 …

 } 

Now create the loggers in the Actor classes like this...

   class Actor1 extends Actor {

      val logger = LoggerFactory.getLogger("Domain1")
      ....


    class Actor2 extends Actor {

      val logger = LoggerFactory.getLogger("Domain2")
      ....

  class Actor3 extends Actor {
      val logger = LoggerFactory.getLogger("Domain1")
      ...

You may refer to this link to for discriminator example

http://www.nurkiewicz.com/2013/04/siftingappender-logging-different.html