question: public boolean sync ( ) { if ( ulog == null ) { return false ; } log . info ( msg ( ) + "START replicas=" + replicas + " nUpdates=" + nUpdates ) ; if ( ! ( ulog . getState ( ) == UpdateLog . State . ACTIVE || ulog . getState ( ) == UpdateLog . State . REPLAYING ) ) { log . error ( msg ( ) + "ERROR, update log not in ACTIVE or REPLAY state. " + ulog ) ; } if ( debug ) { if ( startingVersions != null ) { log . debug ( msg ( ) + "startingVersions=" + startingVersions . size ( ) + " " + startingVersions ) ; } } for ( String replica : replicas ) { requestVersions ( replica ) ; } recentUpdates = ulog . getRecentUpdates ( ) ; try { ourUpdates = recentUpdates . getVersions ( nUpdates ) ; } finally { recentUpdates . close ( ) ; } Collections . sort ( ourUpdates , absComparator ) ; if ( startingVersions != null ) { if ( startingVersions . size ( ) == 0 ) { log . warn ( "no frame of reference to tell if we've missed updates" ) ; return false ; } Collections . sort ( startingVersions , absComparator ) ; ourLowThreshold = percentile ( startingVersions , 0.8f ) ; ourHighThreshold = percentile ( startingVersions , 0.2f ) ; long smallestNewUpdate = Math . abs ( ourUpdates . get ( ourUpdates . size ( ) - 1 ) ) ; if ( Math . abs ( startingVersions . get ( 0 ) ) < smallestNewUpdate ) { log . warn ( msg ( ) + "too many updates received since start - startingUpdates no longer overlaps with our currentUpdates" ) ; return false ; } List < Long > newList = new ArrayList < > ( ourUpdates ) ; for ( Long ver : startingVersions ) { if ( Math . abs ( ver ) < smallestNewUpdate ) { newList . add ( ver ) ; } } ourUpdates = newList ; } else { if ( ourUpdates . size ( ) > 0 ) { ourLowThreshold = percentile ( ourUpdates , 0.8f ) ; ourHighThreshold = percentile ( ourUpdates , 0.2f ) ; } else { log . info ( msg ( ) + "DONE.  We have no versions.  sync failed." ) ; return false ; } } ourUpdateSet = new HashSet < > ( ourUpdates ) ; requestedUpdateSet = new HashSet < > ( ourUpdates ) ; for ( ; ; ) { ShardResponse srsp = shardHandler . takeCompletedOrError ( ) ; if ( srsp == null ) break ; boolean success = handleResponse ( srsp ) ; if ( ! success ) { log . info ( msg ( ) + "DONE. sync failed" ) ; shardHandler . cancelAll ( ) ; return false ; } } log . info ( msg ( ) + "DONE. sync succeeded" ) ; return true ; }
target:  Returns true if peer sync was successful, meaning that this core may not be considered to have the latest updates when considering the last N updates between it and it's peers. A commit is not performed.