water

Class KeySnapshot

java.lang.Object

water.KeySnapshot

public class KeySnapshot
extends java.lang.Object

Convenience class for easy access to user-visible keys in the cloud with enabled caching. This class represents snapshot of user keys currently stored in the cloud and contains methods to retrieve it. It contains all user keys stored in the cloud at one particular point in time (marked by timestamp member variable). Snapshot does not contain the actual values and no values are fetched from remote by requesting new snapshot. KeySnapshot itself is a set of user keys with some additional info (e.g. type and size) and some convenience functions supporting filtering and instantiating of classes pointed to by the keys

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	KeySnapshot.KeyInfo Class containing information about user keys.
static class	KeySnapshot.KVFilter Class to filter keys from the snapshot.

Field Summary

Fields

Modifier and Type	Field and Description
KeySnapshot.KeyInfo[]	_keyInfos
long	timestamp (local) Time of creation.

Method Summary

Methods

Modifier and Type	Method and Description
static KeySnapshot	cache()
<T extends Iced> java.util.Map<java.lang.String,T>	fetchAll(java.lang.Class<T> c)
<T extends Iced> java.util.Map<java.lang.String,T>	fetchAll(java.lang.Class<T> c, boolean exact)
<T extends Iced> java.util.Map<java.lang.String,T>	fetchAll(java.lang.Class<T> c, boolean exact, int offset, int limit)
KeySnapshot	filter(KeySnapshot.KVFilter kvf) Filter the snapshot providing custom filter.
static Key[]	globalKeysOfClass(java.lang.Class clz) Return all the keys of the given class.
static KeySnapshot	globalSnapshot()
static KeySnapshot	globalSnapshot(long timeTolerance) Cache-enabled call to get global key snapshot.
Key[]	keys()
static KeySnapshot	localSnapshot() Get the user keys from this node only.
static KeySnapshot	localSnapshot(boolean homeOnly) Get the user keys from this node only.

Methods inherited from class java.lang.Object

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

Field Detail

_keyInfos

public final KeySnapshot.KeyInfo[] _keyInfos

timestamp

public final long timestamp

(local) Time of creation.

Method Detail

cache

public static KeySnapshot cache()

Returns:

cached version of KeySnapshot

filter

public KeySnapshot filter(KeySnapshot.KVFilter kvf)

Filter the snapshot providing custom filter. Only the keys for which filter returns true will be present in the new snapshot.

Parameters:

kvf - The filter

Returns:

filtered snapshot

keys

public Key[] keys()

Returns:

array of all keys in this snapshot.

globalKeysOfClass

public static Key[] globalKeysOfClass(java.lang.Class clz)

Return all the keys of the given class.

Parameters:

clz - Class

Returns:

array of keys in this snapshot with the given class

fetchAll

public <T extends Iced> java.util.Map<java.lang.String,T> fetchAll(java.lang.Class<T> c)

Type Parameters:

T - Generic class being fetched

Parameters:

c - Class objects of which should be instantiated

Returns:

all objects (of the proper class) pointed to by this key snapshot (and still present in the K/V at the time of invocation).

fetchAll

public <T extends Iced> java.util.Map<java.lang.String,T> fetchAll(java.lang.Class<T> c,
                                                          boolean exact)

Type Parameters:

T - Generic class being fetched

Parameters:

c - Class objects of which should be instantiated

exact - - subclasses will not be included if set.

Returns:

all objects (of the proper class) pointed to by this key snapshot (and still present in the K/V at the time of invocation).

fetchAll

public <T extends Iced> java.util.Map<java.lang.String,T> fetchAll(java.lang.Class<T> c,
                                                          boolean exact,
                                                          int offset,
                                                          int limit)

Type Parameters:

T - Generic class being fetched

Parameters:

c - Class objects of which should be instantiated

exact - - subclasses will not be included if set.

offset - - skip first offset values matching the given type

limit - - produce only up to the limit objects.

Returns:

all objects (of the proper class) pointed to by this key snapshot (and still present in the K/V at the time of invocation).

localSnapshot

public static KeySnapshot localSnapshot()

Get the user keys from this node only. Includes non-local keys which are cached locally.

Returns:

KeySnapshot containing keys from the local K/V.

localSnapshot

public static KeySnapshot localSnapshot(boolean homeOnly)

Get the user keys from this node only.

Parameters:

homeOnly - - exclude the non-local (cached) keys if set

Returns:

KeySnapshot containing keys from the local K/V.

globalSnapshot

public static KeySnapshot globalSnapshot()

Returns:

KeySnapshot containing user keys from all the nodes.

globalSnapshot

public static KeySnapshot globalSnapshot(long timeTolerance)

Cache-enabled call to get global key snapshot. User can provide time tolerance to indicate a how old the snapshot can be.

Parameters:

timeTolerance - - tolerated age of the cache in millis. If the last snapshot is bellow this value, cached version will be returned immediately. Otherwise new snapshot must be obtained by from all nodes.

Returns:

KeySnapshot containing user keys from all the nodes.