Spark doc build process hangs on Failed to load class "org.slf4j.impl.StaticLoggerBinder" - apache-spark

Question

I followed this
https://github.com/apache/spark/blob/master/docs/README.md
to build spark docs,but it hangs on:
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
after half an hour,no further info got printed out.I tried to add slf4j-simple-1.7.12.jar into spark/lib_managed/jars,then rerun
jekyll build
still hang on these messages,how to solve the problem?

Answer 1

For me the solution was adding Logback Classic Module to the classpath:
http://mvnrepository.com/artifact/ch.qos.logback/logback-classic/1.1.7
and removing any other implementations of StaticLoggerBinder.

Answer 2

There's an explanation in the Spark documentation:
http://sparkjava.com/documentation#how-do-i-enable-logging
You might have seen this message when starting Spark:
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J:
See http://www.slf4j.org/codes.html#StaticLoggerBinder for further
details.Copy
To enable logging, just add the following dependency to your project:
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>1.7.21</version>
</dependency>
For Gradle, check this thread for more details:
How to set SLF4J in IntelliJ with Gradle
Then you'll might need to configure slf4j properly, by creating a config file, but that's a different topic. Check this and this if that's the case.