ReconfigurableBase#startReconfigurationTask does not update its cached configuration after a property is reconfigured. This means that configuration values queried via getConf().get(...) can be outdated. One way to fix it is ReconfigurableBase#reconfigurePropertyImpl returns the new effective value of the config setting and caller i.e. ReconfigurableBase will use it to update the configuration.
See discussion on
HDFS-7035 for more background.