@pwendell What I see left are dependencies from third-party libraries on slf4j-api, which is fine. Most depend on 1.7.5 (so good that the version in Spark is bumped to 1.7.5), and a few use 1.6.x, which should be entirely compatible. It's also OK for dependencies to have slf4j-over-log4j12. So AFAICT it's fine in this regard.