org.infinispan.atomic

Interface AtomicMap<K,V>

All Superinterfaces:

Map<K,V>

public interface AtomicMap<K,V>
extends Map<K,V>

This is a special type of Map geared for use in Infinispan. AtomicMaps have two major characteristics:

1. Atomic locking and isolation over the entire collection
2. Fine-grained serialization of deltas

1. Atomic locking and isolation over the entire collection

This allows the entire AtomicMap to be locked when making changes even to certain entries within the map, and also isolates the map for safe reading (see IsolationLevel while concurrent writes may be going on.

2. Fine-grained serialization of deltas

AtomicMap implementations also implement the DeltaAware interface. This powerful interface allows the generation and application of deltas, and requires that implementations are capable of tracking changes made to it during the course of a transaction. This helps since when performing replications to update remote nodes, the entire map need not be serialized and transported all the time, as serializing and transporting Delta instances would work just as well, and typically be much smaller and hence faster to serialize and transport.

Applications requiring either or both of the characteristics described above are encouraged to use AtomicMaps with Infinispan, however the real benefit is often only seen where a combination of both characteristics are required.

Usage

AtomicMaps should be constructed and "registered" with Infinispan using the AtomicMapLookup helper. This helper ensures threadsafe construction and registration of AtomicMap instances in Infinispan's data container. E.g.:
AtomicMap<String, Integer> map = AtomicMapLookup.getAtomicMap(cache, "my_atomic_map_key");

Referential Integrity
It is important to note that concurrent readers of an AtomicMap will essentially have the same view of the contents of the underlying structure, but since AtomicMaps use internal proxies, readers are isolated from concurrent writes and IsolationLevel.READ_COMMITTED and IsolationLevel.REPEATABLE_READ semantics are guaranteed. However, this guarantee is only present if the values stored in an AtomicMap are immutable (e.g., Strings, primitives, and other immutable types).

Mutable value objects which happen to be stored in an AtomicMap may be updated and, prior to being committed, or even replaced in the map, be visible to concurrent readers. Hence, AtomicMaps are not suitable for use with mutable value objects.

This interface, for all practical purposes, is just a marker interface that indicates that maps of this type will be locked atomically in the cache and replicated in a fine grained manner, as it does not add any additional methods to Map.

Since:

4.0

Author:

Manik Surtani

See Also:

DeltaAware, Delta, AtomicHashMap, AtomicMapLookup