com.apple.foundationdb

Class LocalityUtil

java.lang.Object

com.apple.foundationdb.LocalityUtil

public class LocalityUtil
extends java.lang.Object

The FoundationDB API comes with a set of functions for discovering the storage locations of keys within your cluster. This information can be useful for advanced users who wish to take into account the location of keys in the design of applications or processes.

Method Summary

Modifier and Type	Method and Description
static java.util.concurrent.CompletableFuture<java.lang.String[]>	getAddressesForKey(Transaction tr, byte[] key) Returns a list of public network addresses as strings, one for each of the storage servers responsible for storing key and its associated value.
static CloseableAsyncIterator<byte[]>	getBoundaryKeys(Database db, byte[] begin, byte[] end) Returns a CloseableAsyncIterator of keys k such that begin <= k < end and k is located at the start of a contiguous range stored on a single server. This method is not transactional.
static CloseableAsyncIterator<byte[]>	getBoundaryKeys(Transaction tr, byte[] begin, byte[] end) Returns a CloseableAsyncIterator of keys k such that begin <= k < end and k is located at the start of a contiguous range stored on a single server. This method is not transactional.

Methods inherited from class java.lang.Object

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

Method Detail

getBoundaryKeys

public static CloseableAsyncIterator<byte[]> getBoundaryKeys(Database db,
                                                             byte[] begin,
                                                             byte[] end)

Returns a CloseableAsyncIterator of keys k such that begin <= k < end and k is located at the start of a contiguous range stored on a single server.

This method is not transactional. The returned boundaries are an estimate and may not represent the exact boundary locations at any database version.

Parameters:

db - the database to query

begin - the inclusive start of the range

end - the exclusive end of the range

Returns:

an sequence of keys denoting the start of single-server ranges

getBoundaryKeys

public static CloseableAsyncIterator<byte[]> getBoundaryKeys(Transaction tr,
                                                             byte[] begin,
                                                             byte[] end)

Returns a CloseableAsyncIterator of keys k such that begin <= k < end and k is located at the start of a contiguous range stored on a single server.

This method is not transactional. The returned boundaries are an estimate and may not represent the exact boundary locations at any database version. The passed Transaction is not used for reads directly, instead it is used to get access to associated Database. As a result, options (such as retry limit) set on the passed Transaction will not be applied. If, however, the passed Transaction has already gotten a read version there is some latency advantage to using this form of the method. Also, if the database is unavailable prior to the function call, any timeout set on the passed Transaction will still trigger.

Parameters:

tr - the transaction on which to base the query

begin - the inclusive start of the range

end - the exclusive end of the range

Returns:

an sequence of keys denoting the start of single-server ranges

getAddressesForKey

public static java.util.concurrent.CompletableFuture<java.lang.String[]> getAddressesForKey(Transaction tr,
                                                                                            byte[] key)

Returns a list of public network addresses as strings, one for each of the storage servers responsible for storing key and its associated value. If locality information is not available, the returned future will carry a FDBException locality_information_unavailable.

Parameters:

tr - the transaction in which to gather location information

key - the key for which to gather location information

Returns:

a list of addresses in string form