Package org.apache.curator.framework.recipes.cache

Interface CuratorCache

All Superinterfaces:

AutoCloseable, Closeable, CuratorCacheAccessor

All Known Subinterfaces:

CuratorCacheBridge

public interface CuratorCache
extends Closeable, CuratorCacheAccessor

A utility that attempts to keep the data from a node locally cached. Optionally the entire tree of children below the node can also be cached. Will respond to update/create/delete events, pull down the data, etc. You can register listeners that will get notified when changes occur.

IMPORTANT - Due to how ZooKeeper works you will not get notified of every single event. For example during a network partition the cache will not get events. Imagine the following scenario:

• Pre-network partition the cache contains "/foo" and "/foo/bar"
• A network partition occurs and your Curator client loses connection to the server
• Image another client that isn't partitioned, deletes "/foo/bar" and then a third client re-creates "/foo/bar"
• Your client's partition is fixed. The cache will only see one change - the third client's re-create

Additionally, remember that ZooKeeper is an eventual consistent system. Always use ZNode version numbers when updating nodes.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static enum	CuratorCache.Options	cache build options

Method Summary

Modifier and Type	Method	Description
static CuratorCacheBridgeBuilder	bridgeBuilder(CuratorFramework client, String path)	Start a Curator Cache Bridge builder.
static CuratorCache	build(CuratorFramework client, String path, CuratorCache.Options... options)	Return a Curator Cache for the given path with the given options using a standard storage instance
static CuratorCacheBuilder	builder(CuratorFramework client, String path)	Start a Curator Cache builder
void	close()	Close the cache, stop responding to events, etc.
Optional<ChildData>	get(String path)	Return an entry from storage
Listenable<CuratorCacheListener>	listenable()	Return the listener container so that listeners can be registered to be notified of changes to the cache
int	size()	Return the current number of entries in storage
void	start()	Start the cache.
Stream<ChildData>	stream()	Return a stream over the storage entries.

Method Details

build

static CuratorCache build(CuratorFramework client,
 String path,
 CuratorCache.Options... options)

Return a Curator Cache for the given path with the given options using a standard storage instance

Parameters:

client - Curator client

path - path to cache

options - any options

Returns:

cache (note it must be started via start()

builder

static CuratorCacheBuilder builder(CuratorFramework client,
 String path)

Start a Curator Cache builder

Parameters:

client - Curator client

path - path to cache

Returns:

builder

bridgeBuilder

static CuratorCacheBridgeBuilder bridgeBuilder(CuratorFramework client,
 String path)

Start a Curator Cache Bridge builder. A Curator Cache Bridge is a facade that uses CuratorCache if persistent watches are available or TreeCache otherwise (i.e. if you are using ZooKeeper 3.5.x).

Parameters:

client - Curator client

path - path to cache

Returns:

bridge builder

start

void start()

Start the cache. This will cause a complete refresh from the cache's root node and generate events for all nodes found, etc.

close

void close()

Close the cache, stop responding to events, etc.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

listenable

Listenable<CuratorCacheListener> listenable()

Return the listener container so that listeners can be registered to be notified of changes to the cache

Returns:

listener container

get

Optional<ChildData> get(String path)

Return an entry from storage

Specified by:

get in interface CuratorCacheAccessor

Parameters:

path - path to get

Returns:

entry or empty()

size

int size()

Return the current number of entries in storage

Specified by:

size in interface CuratorCacheAccessor

Returns:

number of entries

stream

Stream<ChildData> stream()

Return a stream over the storage entries. Note: for a standard storage instance, the stream behaves like a stream returned by ConcurrentHashMap.entrySet()

Specified by:

stream in interface CuratorCacheAccessor

Returns:

stream over entries