Many popular Apache projects use slf4j now to avoid unnecessary conflicts, like the Apache Spark, Apache Flink，etc. slf4j is a bridge jar/interface for log4j/log4j2 to avoid conflicts, log4j2 is also a easy-conflicting jar even though it has more stable API than log4j
As a bridge jar, slf4j relies on an impl jar like log4j2, that means both jars are needed to a complete logger system. For Hudi developers, we suggest always using slf4j instead for subsequent changes. Related change: https://github.com/apache/hudi/pull/7955 Best, Danny
