Starting the Member and Client

Having installed Hazelcast, you can get started.

In this short tutorial, you perform the following activities:

  1. Create a simple Java application using the Hazelcast distributed map and queue.

  2. Run our application twice to have a cluster with two members (JVMs).

  3. Connect to our cluster from another Java application by using the Hazelcast Native Java Client API.

Let’s begin.

  • The following code starts the first Hazelcast member and creates and uses the customers map and queue.

            Config cfg = new Config();
            HazelcastInstance instance = Hazelcast.newHazelcastInstance(cfg);
            Map<Integer, String> mapCustomers = instance.getMap("customers");
            mapCustomers.put(1, "Joe");
            mapCustomers.put(2, "Ali");
            mapCustomers.put(3, "Avi");
            System.out.println("Customer with key 1: "+ mapCustomers.get(1));
            System.out.println("Map Size:" + mapCustomers.size());
            Queue<String> queueCustomers = instance.getQueue("customers");
            System.out.println("First customer: " + queueCustomers.poll());
            System.out.println("Second customer: "+ queueCustomers.peek());
            System.out.println("Queue size: " + queueCustomers.size());
  • Run this GettingStarted class a second time to get the second member started. The members form a cluster and the output is similar to the following.

    Members {size:2, ver:2} [
        Member []:5701 - e40081de-056a-4ae5-8ffe-632caf8a6cf1 this
        Member []:5702 - 93e82109-16bf-4b16-9c87-f4a6d0873080

    Here, you can see the size of your cluster (size) and member list version (ver). The member list version is incremented when changes happen to the cluster, e.g., a member leaving from or joining to the cluster.

    The above member list format is introduced with Hazelcast 3.9. You can enable the legacy member list format, which was used for the releases before Hazelcast 3.9, using the system property hazelcast.legacy.memberlist.format.enabled. See the System Properties appendix. The following is an example for the legacy member list format:

    Members [2] {
        Member []:5701 - c1ccc8d4-a549-4bff-bf46-9213e14a9fd2 this
        Member []:5702 - 33a82dbf-85d6-4780-b9cf-e47d42fb89d4
  • Now, add the hazelcast-client-<version>.jar library to your classpath. This is required to use a Hazelcast client.

  • The following code starts a Hazelcast Client, connects to our cluster, and prints the size of the customers map.

    public class GettingStartedClient {
        public static void main( String[] args ) {
            ClientConfig clientConfig = new ClientConfig();
            HazelcastInstance client = HazelcastClient.newHazelcastClient( clientConfig );
            IMap map = client.getMap( "customers" );
            System.out.println( "Map Size:" + map.size() );
  • When you run it, you see the client properly connecting to the cluster and printing the map size as 3.

Hazelcast also offers a tool, Management Center, that enables you to monitor your cluster. You can download it from Hazelcast website’s download page. You can use it to monitor your maps, queues and other distributed data structures and members. Please see the Hazelcast Management Center Reference Manual for usage explanations.

By default, Hazelcast uses multicast to discover other members that can form a cluster. If you are working with other Hazelcast developers on the same network, you may find yourself joining their clusters under the default settings. Hazelcast provides a way to segregate clusters within the same network when using multicast. See the Creating Cluster Groups section for more information. Alternatively, if you do not wish to use the default multicast mechanism, you can provide a fixed list of IP addresses that are allowed to join.

Multicast mechanism is not recommended for production since UDP is often blocked in production environments and other discovery mechanisms are more definite. See the Discovery Mechanisms section.
You can also check the video tutorials here.