Hazelcast Overview

This is just an evaluation summary. A shortened version of Hazelcast documentation. I pointed out the most important facts about it.

Hazelcast allows for distributing application data across cluster nodes. It is a peer-to-peer solution to avoid single point of failure.

• Data in the cluster is almost evenly distributed (partitioned) across all nodes. So each node carries ~ (1/n * total-data) + backups , n being the number of nodes in the cluster.
• Although it may be setup as Near Cache which disables even distribution
• How can this work ? Hazelcast allows you to run distributed queries on distributed map.
• Instead of getting entire entry set and iterating it locally, look for certain entries you are interested in
• map.values(new SqlPredicate("active AND age < 30"));
• OR
• map.values(e.is("active").and(e.get("age").lessThan(30)));
• queries run on each member in parallel and only the caller returns the results

• Distributed Events
• Hazelcast allows you to register for entry events to get notified when entries are added, updated or removed

• MembershipListener for cluster membership events
• InstanceListener for distributed instance creation and destroy events
• MigrationListener for partition migration start and complete events
• LifecycleListener for HazelcastInstance lifecycle events
• EntryListener for IMap and MultiMap entry events
• ItemListener for IQueue, ISet and IList item events
• MessageListener for ITopic message events

• Hazelcast allows you to load and store the distributed map entries from/to a persistent datastore such as relational database. Just supply it with a class that implements MapLoader and MapStore.
• Existing implementations for JPA spec and MongoDB

• Integration with Spring
• overall configuration
• registering distributed collections and maps and have them injected into beans
• caching via com.hazelcast.spring.cache.HazelcastCacheManager
• spring-data : JPA & MongoDB

• Transaction context :  txn.begin(); txn.commit() / txn.rollback();

• Hazelcast WM allows you to cluster user http sessions automatically
• Distributed Execution - running tasks in parallel within cluster
  
• Clients
• enables you to do all Hazelcast operations without being a member of the cluster. It connects to one of the cluster members and delegates all cluster wide operations to it
• Java Client
• Rest Client
• You can put a new key1/value1 entry into map “stocks” by issuing HTTP POST call to http://10.20.17.1:5701/hazelcast/rest/maps/stocks/key1

• All distributed objects such as your key and value objects have to be Serializable !
• Hazelcast has a very nice web based Management Center