How can I configure system properties or logback configuration variables from typesafe config?

Question

I have variables with defaults in my logback.xml configuration file, and I would like to be able to optionally set these variables from my typesafe config application.conf file.

I am deploying the application using one-jar, and the application.conf file packaged up in the deployable jar contains defaults. I pass -Dconfig.file=foo.conf on execution to provide the path to a server-specific config file.

Right now I can also pass -Dlog.level and other variables to override my defaults in logback.xml, and I also have to pass -Dfile.encoding=UTF-8 on the command line. I'm looking for a way to be able to specify these properties in the typesafe config instead of on the command line. It feels like there should be a way to do it, but I can't find the magic words.

logback.xml:

<configuration>
    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${log.path:-logs/}/${log.file:-myLog.log}</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <!-- daily rollover -->
            <fileNamePattern>logFile.%d{yyyy-MM-dd}.log</fileNamePattern>

            <!-- keep 15 days' worth of history -->
            <maxHistory>${log.history.days:-15}</maxHistory>
        </rollingPolicy>

        <encoder>
            <pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern>
        </encoder>
    </appender>

    <root level="${log.level:-INFO}">
        <appender-ref ref="FILE" />
    </root>
</configuration>

application.conf (bundled):

akka {
    log-config-on-start = false
    event-handlers = ["akka.event.slf4j.Slf4jEventHandler"]
}

sample server-specific app.conf:

include "/application.conf"

akka.log-config-on-start = true

log.level = WARN // this is what I'd LIKE to be able to do

How I'm currently running the app:

java -Dfile.encoding=UTF-8 -Dconfig.file=myApp.conf -Dlog.level=WARN -jar myApp_2.10-0.1-one-jar.jar 

Answer 1

I chose to programmatically configure logback having typesafe config. It turned out to be easy.

def enableRemoteLogging(config: Config) = {
    val ctx = LoggerFactory.getILoggerFactory.asInstanceOf[LoggerContext]

    val gelf = new GelfAppender
    gelf.setGraylog2ServerHost(config.getString("logging.remote.server"))
    gelf.setUseLoggerName(true)
    gelf.setUseThreadName(true)
    gelf.setUseMarker(true)
    gelf.setIncludeFullMDC(true)
    gelf.setContext(ctx)
    gelf.start()

    LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME)
      .asInstanceOf[ch.qos.logback.classic.Logger]
      .addAppender(gelf)
  }

Answer 2

You can use the PropertyDefiner interface that logback provides. Non trivial scaffolding but allows you to configure using XML instead of within your application. E.g.:

package com.myapp;

import ch.qos.logback.core.PropertyDefinerBase;
import com.typesafe.config.ConfigFactory;

public class TypesafeConfigPropertyDefiner extends PropertyDefinerBase {

    private String propertyName;

    @Override
    public String getPropertyValue() {
        return ConfigFactory.load().getString( propertyName );
    }

    public void setPropertyName( String propertyName ) {
        this.propertyName = propertyName;
    }
}

Then, in your logback.xml file:

<configuration>
    <define name="loglevel" class="com.myapp.TypesafeConfigPropertyDefiner">
        <propertyName>myapp.logging.loglevel</propertyName>
    </define>
    <root level="${loglevel}">
       ...
    </root>
</configuration>

Now, the above logback.xml file will read myapp.logging.loglevel from your typesafe config file (e.g. application.conf).

Answer 3

I'm not familiar with Logback, but a normal Akka application ships with default settings in its reference.conf, and you override these settings in an application.conf. It sounds like you want to add a third layer of configuration, which is certainly your right!

The easiest way I can see is to change your application.conf to include your foo.conf rather than the other way around. That way Akka will load the application.conf, which will then load foo.conf.

But that may not work if you need a differently-named conf file for each JAR distribution. In which case I recommend you look into Merging Config Trees to programmatically load and combine configuration. Actually, Reading configuration from a custom location in the Akka Configuration docs is almost exactly what you want, except you will want to load myConfig from a classpath resource rather than by parsing a string (see the Typesafe Config docs to find out how to do that).

Regarding the Logback configuration, like I said, I don't know Logback. But you can read values out an Typesafe configuration like so, and you can set the Logback root logger level like so.