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= Logging

Delta Lake uses[log4j] for logging (as does Apache Spark itself).

== [[levels]] Logging Levels

The valid logging levels are[log4j's Levels] (from most specific to least):

  • OFF (most specific, no logging)
  • FATAL (most specific, little data)
  • WARN
  • INFO
  • TRACE (least specific, a lot of data)
  • ALL (least specific, all data)

== [[log4j-properties]] conf/

You can set up the default logging for Delta applications in conf/ of the Spark installation. Use Spark's conf/ 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:

[source, scala]

fork in run := true javaOptions in run ++= Seq( "-Dlog4j.debug=true", "") outputStrategy := Some(StdoutOutput)

With the above configuration file should be on CLASSPATH which can be in src/main/resources directory (that is included in CLASSPATH by default).

When run starts, you should see the following output in sbt:

[spark-activator]> run
[info] Running StreamingApp
log4j: Trying to find [] using context classloader sun.misc.Launcher$AppClassLoader@1b6d3586.
log4j: Using URL [file:.../classes/] for automatic log4j configuration.
log4j: Reading configuration from URL file:.../classes/

Last update: 2020-09-27