public synchronized List<String> setLevel(String namespace, Level level) {
        Objects.requireNonNull(namespace, "Logging namespace may not be null");
        Objects.requireNonNull(level, "Level may not be null");

        log.info("Setting level of namespace {} and children to {}", namespace, level);
        List<org.apache.log4j.Logger> childLoggers = loggers(namespace);

        List<String> result = new ArrayList<>();
        for (org.apache.log4j.Logger logger: childLoggers) {
            setLevel(logger, level);
            result.add(logger.getName());
        }
        Collections.sort(result);

        return result;
    }
Set the level for the specified logger and all of its children
@param namespace the name of the logger to adjust along with its children; may not be null
@param level the level to set for the logger and its children; may not be null
@return all loggers that were affected by this action, sorted by their natural ordering;
may be empty, but never null
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/Loggers.java