Delta Lake uses http://logging.apache.org/log4j[log4j] for logging (as does Apache Spark itself).
== [[levels]] Logging Levels
The valid logging levels are http://logging.apache.org/log4j/2.x/log4j-api/apidocs/index.html[log4j's Levels] (from most specific to least):
OFF(most specific, no logging)
FATAL(most specific, little data)
TRACE(least specific, a lot of data)
ALL(least specific, all data)
== [[log4j-properties]] conf/log4j.properties
You can set up the default logging for Delta applications in
conf/log4j.properties of the Spark installation. Use Spark's
conf/log4j.properties.template as a starting point.
== [[sbt]] sbt
When running a Delta application from within sbt using
run task, you can use the following
build.sbt to configure logging levels:
fork in run := true javaOptions in run ++= Seq( "-Dlog4j.debug=true", "-Dlog4j.configuration=log4j.properties") outputStrategy := Some(StdoutOutput)
With the above configuration
log4j.properties file should be on CLASSPATH which can be in
src/main/resources directory (that is included in CLASSPATH by default).
run starts, you should see the following output in sbt:
[spark-activator]> run [info] Running StreamingApp log4j: Trying to find [log4j.properties] using context classloader sun.misc.Launcher$AppClassLoader@1b6d3586. log4j: Using URL [file:.../classes/log4j.properties] for automatic log4j configuration. log4j: Reading configuration from URL file:.../classes/log4j.properties