question: private CompletableFuture < Void > apply ( ConfigurationEntry entry ) { log . release ( entry . getIndex ( ) ) ; return CompletableFuture . completedFuture ( null ) ; }
target:  Applies a configuration entry to the internal state machine. <p> Configuration entries are applied to internal server state when written to the log. Thus, no significant logic needs to take place in the handling of configuration entries. We simply release the previous configuration entry since it was overwritten by a more recent committed configuration entry.