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User Defined Services

In the case of special/custom needs, Hazelcast's SPI (Service Provider Interface) module allows users to develop their own distributed data structures and services.

Sample Case

Throughout this section, we create a distributed counter that will be the guide to reveal the Hazelcast SPI usage.

Here is our counter.

public interface Counter{
   int inc(int amount);
}

This counter will have the following features:

  • It will be stored in Hazelcast.
  • Different cluster members can call it.
  • It will be scalable, meaning that the capacity for the number of counters scales with the number of cluster members.
  • It will be highly available, meaning that if a member hosting this counter goes down, a backup will be available on a different member.

All these features will be realized with the steps below. In each step, a new functionality to this counter will be added.

  1. Create the class.
  2. Enable the class.
  3. Add properties.
  4. Place a remote call.
  5. Create the containers.
  6. Enable partition migration.
  7. Create the backups.