org.janusgraph.diskstorage

Interface IDAuthority

All Known Implementing Classes:

AbstractIDAuthority, ConsistentKeyIDAuthority

public interface IDAuthority

Handles the unique allocation of ids. Returns blocks of ids that are uniquely allocated to the caller so that they can be used to uniquely identify elements. *

Author:

Matthias Broecheler ([email protected])

Method Summary

Modifier and Type	Method and Description
void	close() Closes the IDAuthority and any underlying storage backend.
IDBlock	getIDBlock(int partition, int idNamespace, Duration timeout) Returns a block of new ids in the form of IDBlock.
List<KeyRange>	getLocalIDPartition() Returns the lower and upper limits of the key range assigned to this local machine as an array with two entries.
String	getUniqueID() Return the globally unique string used by this IDAuthority instance to recognize its ID allocations and distinguish its allocations from those belonging to other IDAuthority instances.
void	setIDBlockSizer(IDBlockSizer sizer) Sets the IDBlockSizer to be used by this IDAuthority.
boolean	supportsInterruption() Whether getIDBlock(int, int, Duration) may be safely interrupted.

Method Detail

getIDBlock

IDBlock getIDBlock(int partition,
                   int idNamespace,
                   Duration timeout)
            throws BackendException

Returns a block of new ids in the form of IDBlock. It is guaranteed that the block of ids for the particular partition id is uniquely assigned, that is, the block of ids has not been previously and will not subsequently be assigned again when invoking this method on the local or any remote machine that is connected to the underlying storage backend.

In other words, this method has to ensure that ids are uniquely assigned per partition.

It is furthermore guaranteed that any id of the returned IDBlock is smaller than the upper bound for the given partition as read from the IDBlockSizer set on this IDAuthority and that the number of ids returned is equal to the block size of the IDBlockSizer.

Parameters:

partition - Partition for which to request an id block

idNamespace - namespace for ids within a partition

timeout - When a call to this method is unable to return a id block before this timeout elapses, the implementation must give up and throw a StorageException ASAP

Returns:

a range of ids for the partition parameter

Throws:

BackendException

getLocalIDPartition

List<KeyRange> getLocalIDPartition()
                            throws BackendException

Returns the lower and upper limits of the key range assigned to this local machine as an array with two entries.

Returns:

Throws:

BackendException

setIDBlockSizer

void setIDBlockSizer(IDBlockSizer sizer)

Sets the IDBlockSizer to be used by this IDAuthority. The IDBlockSizer specifies the block size for each partition guaranteeing that the same partition will always be assigned the same block size.

The IDBlockSizer cannot be changed for an IDAuthority that has already been used (i.e. after invoking getIDBlock(int, int, Duration).

Parameters:

sizer - The IDBlockSizer to be used by this IDAuthority

close

void close()
    throws BackendException

Closes the IDAuthority and any underlying storage backend.

Throws:

BackendException

getUniqueID

String getUniqueID()

Return the globally unique string used by this IDAuthority instance to recognize its ID allocations and distinguish its allocations from those belonging to other IDAuthority instances. This should normally be the value of GraphDatabaseConfiguration.UNIQUE_INSTANCE_ID, though that's not strictly technically necessary.

Returns:

unique ID string

supportsInterruption

boolean supportsInterruption()

Whether getIDBlock(int, int, Duration) may be safely interrupted.

Returns:

true if interruption is allowed, false if it is not