@marmbrus So I read up on this a bit more and as I understand the log4j bridge should not increase the log output rate so there shouldn't be any performance issues (confirmed that by a microbenchmark). The upper bound is Parquet's own default log level (INFO) and log4j can only filter from there. I got the bridge working now, too, although it still requires setting the forwarding logger after Parquet has initialized its own default logger. Anyway.. it's better than before and I will push the commits shortly.