Package org.syncany.operations.down

Class DatabaseReconciliator

java.lang.Object

org.syncany.operations.down.DatabaseReconciliator

public class DatabaseReconciliator
extends java.lang.Object

The database reconciliator implements various parts of the sync down algorithm (see also: DownOperation). Its main responsibility is to compare the local database to the other clients' delta databases. The final goal of the algorithms described in this class is to determine a winning MemoryDatabase (or better: a winning DatabaseBranch) of a client.

All algorithm parts largely rely on the comparison of a client's database branch, i.e. its committed set of DatabaseVersions. Instead of comparing the entire database versions of the different clients, however, the comparisons solely rely on the DatabaseVersionHeaders. In particular, most of them only compare the VectorClock. If the vector clocks are in conflict (= simultaneous), the local timestamp is used as a final decision (oldest wins).

Algorithm:

1. Input: Local branch, unknown remote branches
2. Sort the databaseversions by vectorclocks, tiebreaking with timestamps.
3. Walk through the sorted list and construct the winning branch.

See Also:

DownOperation, VectorClock

Constructor Summary

Constructors

Constructor	Description
DatabaseReconciliator()

Method Summary

Modifier and Type	Method	Description
DatabaseBranch	findLosersPruneBranch(DatabaseBranch losersBranch, DatabaseBranch winnersBranch)
java.util.Map.Entry<java.lang.String,DatabaseBranch>	findWinnerBranch(DatabaseBranches allBranches)	Implements the core synchronization algorithm as described in the class description.
DatabaseBranch	findWinnersApplyBranch(DatabaseBranch losersBranch, DatabaseBranch winnersBranch)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DatabaseReconciliator

public DatabaseReconciliator()

Method Detail

findWinnerBranch

public java.util.Map.Entry<java.lang.String,DatabaseBranch> findWinnerBranch(DatabaseBranches allBranches)
                                                                            throws java.lang.Exception

Implements the core synchronization algorithm as described in the class description.

Parameters:

allBranches - All branches of all machines (including local)

Returns:

Returns the branch of the winning client

Throws:

java.lang.Exception

findLosersPruneBranch

public DatabaseBranch findLosersPruneBranch(DatabaseBranch losersBranch,
                                            DatabaseBranch winnersBranch)

findWinnersApplyBranch

public DatabaseBranch findWinnersApplyBranch(DatabaseBranch losersBranch,
                                             DatabaseBranch winnersBranch)