Logging configurations mess up in the presence of multiple bindings for SLF4J

[pubudu91]

When there are multiple bindings available for SLF4J in the class path, it messes with the logging configuration. According to SLF4J [1], the way a binding is selected is dependent on the JVM and therefore, should be considered a random selection. This issue may be possible to solve with SLF4J 1.8. But currently, it is still in alpha stage.

This will be an issue if a user puts a 3rd party library which has a logging framework embedded in it to the <BALLERINA_HOME>/bre/lib directory.

To further illustrate this issue, the following is a normal log output to the console from a simple Ballerina main program.

2017-06-30 17:00:58,658  INFO  [com.xyz] - Inside package 'com.xyz' 
2017-06-30 17:00:58,663  INFO  [com.abc] - Inside package 'com.abc' 
2017-06-30 17:00:58,664  ERROR [com.abc] - Error inside package 'com.abc'

Given below is the result of executing the same program, but this time, a library with Log4J embedded in it (activemq-all-5.14.0.jar) was placed in <BALLERINA_HOME>/bre/lib directory.

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/pubudu/products/ballerina-tools-0.89/bre/lib/activemq-all-5.14.0.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/pubudu/products/ballerina-tools-0.89/bre/lib/slf4j-jdk14-1.7.22.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
 INFO | Inside package 'com.xyz'
 INFO | Inside package 'com.abc'
ERROR | Error inside package 'com.abc'

As it can be seen from the last 3 lines, the log format is not the format we specified.

[1] https://www.slf4j.org/codes.html#multiple_bindings

[MadhukaHarith92]

SLF4J dependency is removed in https://github.com/ballerina-platform/module-ballerina-log/pull/116.

[pubudu91]

I don't think removing it from just the log module would fix this issue. But removing the dependency on a log library would indeed fix the user log format messing up issue. This is not an std lib issue, rather a general issue in the distribution.

[MadhukaHarith92]

@pubudu91 Ack. Transferred the issue to ballerina-distribution.