Starting 2 hazelcast instances synchronously on a single machine (with hazelcast.initial.min.cluster.size=2)

Question

How can I configure Hazelcast (optimally the version I currently use: 3.1.2) to run 2 hazelcast instances on a single machine, and block the first instance during startup until both instances are present?

hazelcast.initial.min.cluster.size

The blocking behavior described above can be implemented with the help of hazelcast.initial.min.cluster.size when running both instances on different machines: With the configuration:

Config cfg = new Config(); 
cfg.setProperty("hazelcast.initial.min.cluster.size",
  Integer.toString(minimumInitialMembersInHazelCluster));
cfg.getGroupConfig().setName(clusterName);
hazelInst = Hazelcast.newHazelcastInstance(cfg);

run on different machines, I get the output

Apr 15, 2014 9:31:39 AM com.hazelcast.instance.DefaultAddressPicker
INFO: Prefer IPv4 stack is true.
Apr 15, 2014 9:31:39 AM com.hazelcast.instance.DefaultAddressPicker
INFO: Picked Address[192.168.31.105]:5701, using socket ServerSocket[addr=/0:0:0:0:0:0:0:0,localport=5701], bind any local is true
Apr 15, 2014 9:31:40 AM com.hazelcast.system
INFO: [192.168.31.105]:5701 [dev] Hazelcast Community Edition 3.1.2 (20131120) starting at Address[192.168.31.105]:5701
Apr 15, 2014 9:31:40 AM com.hazelcast.system
INFO: [192.168.31.105]:5701 [dev] Copyright (C) 2008-2013 Hazelcast.com
Apr 15, 2014 9:31:40 AM com.hazelcast.instance.Node
INFO: [192.168.31.105]:5701 [dev] Creating MulticastJoiner
Apr 15, 2014 9:31:40 AM com.hazelcast.core.LifecycleService
INFO: [192.168.31.105]:5701 [dev] Address[192.168.31.105]:5701 is STARTING
Apr 15, 2014 9:31:43 AM com.hazelcast.cluster.MulticastJoiner
INFO: [192.168.31.105]:5701 [dev] 


Members [1] {
    Member [192.168.31.105]:5701 this
}

Apr 15, 2014 9:31:43 AM com.hazelcast.core.LifecycleService
INFO: [192.168.31.105]:5701 [dev] Address[192.168.31.105]:5701 is STARTED
Apr 15, 2014 9:31:43 AM HazelMultiInstanceExp <init>
SEVERE: debug: joined via JoinConfig{multicastConfig=MulticastConfig [enabled=true, multicastGroup=224.2.2.3, multicastPort=54327, multicastTimeToLive=32, multicastTimeoutSeconds=2, trustedInterfaces=[]], tcpIpConfig=TcpIpConfig [enabled=false, connectionTimeoutSeconds=5, members=[], requiredMember=null], awsConfig=AwsConfig{enabled=false, region='us-east-1', securityGroupName='null', tagKey='null', tagValue='null', hostHeader='ec2.amazonaws.com', connectionTimeoutSeconds=5}} with 1 members.
Apr 15, 2014 9:31:43 AM com.hazelcast.instance.DefaultAddressPicker
INFO: Prefer IPv4 stack is true.
Apr 15, 2014 9:31:43 AM com.hazelcast.instance.DefaultAddressPicker
INFO: Picked Address[192.168.31.105]:5702, using socket ServerSocket[addr=/0:0:0:0:0:0:0:0,localport=5702], bind any local is true
Apr 15, 2014 9:31:43 AM com.hazelcast.system
INFO: [192.168.31.105]:5702 [dev] Hazelcast Community Edition 3.1.2 (20131120) starting at Address[192.168.31.105]:5702
Apr 15, 2014 9:31:43 AM com.hazelcast.system
INFO: [192.168.31.105]:5702 [dev] Copyright (C) 2008-2013 Hazelcast.com
Apr 15, 2014 9:31:43 AM com.hazelcast.instance.Node
INFO: [192.168.31.105]:5702 [dev] Creating MulticastJoiner
Apr 15, 2014 9:31:43 AM com.hazelcast.core.LifecycleService
INFO: [192.168.31.105]:5702 [dev] Address[192.168.31.105]:5702 is STARTING
Apr 15, 2014 9:31:43 AM com.hazelcast.nio.SocketConnector
INFO: [192.168.31.105]:5702 [dev] Connecting to /192.168.31.105:5701, timeout: 0, bind-any: true
Apr 15, 2014 9:31:43 AM com.hazelcast.nio.SocketAcceptor
INFO: [192.168.31.105]:5701 [dev] Accepting socket connection from /192.168.31.105:60803
Apr 15, 2014 9:31:43 AM com.hazelcast.nio.TcpIpConnectionManager
INFO: [192.168.31.105]:5702 [dev] 60803 accepted socket connection from /192.168.31.105:5701
Apr 15, 2014 9:31:43 AM com.hazelcast.nio.TcpIpConnectionManager
INFO: [192.168.31.105]:5701 [dev] 5701 accepted socket connection from /192.168.31.105:60803
Apr 15, 2014 9:31:49 AM com.hazelcast.cluster.ClusterService
INFO: [192.168.31.105]:5702 [dev] 

Members [2] {
    Member [192.168.31.105]:5701
    Member [192.168.31.105]:5702 this
}

but run with two instances on one machine, I get

Apr 15, 2014 9:25:14 AM com.hazelcast.instance.DefaultAddressPicker
INFO: Prefer IPv4 stack is true.
Apr 15, 2014 9:25:14 AM com.hazelcast.instance.DefaultAddressPicker
INFO: Picked Address[192.168.31.105]:5701, using socket ServerSocket[addr=/0:0:0:0:0:0:0:0,localport=5701], bind any local is true
Apr 15, 2014 9:25:15 AM com.hazelcast.system
INFO: [192.168.31.105]:5701 [test3] Hazelcast Community Edition 3.1.2 (20131120) starting at Address[192.168.31.105]:5701
Apr 15, 2014 9:25:15 AM com.hazelcast.system
INFO: [192.168.31.105]:5701 [test3] Copyright (C) 2008-2013 Hazelcast.com
Apr 15, 2014 9:25:15 AM com.hazelcast.instance.Node
INFO: [192.168.31.105]:5701 [test3] Creating MulticastJoiner
Apr 15, 2014 9:25:15 AM com.hazelcast.core.LifecycleService
INFO: [192.168.31.105]:5701 [test3] Address[192.168.31.105]:5701 is STARTING
Apr 15, 2014 9:25:18 AM com.hazelcast.cluster.MulticastJoiner
INFO: [192.168.31.105]:5701 [test3] 


Members [1] {
    Member [192.168.31.105]:5701 this
}

Apr 15, 2014 9:25:18 AM com.hazelcast.instance.HazelcastInstanceImpl
INFO: [192.168.31.105]:5701 [test3] HazelcastInstance waiting for cluster size of 2

with the last INFO message repeated ad infinitum.

So the cluster size is the number of nodes in the cluster, not the number of hazelcast instances?

Blocking behavior on a single machine

I use cfg.setProperty("hazelcast.initial.min.cluster.size","2") so the two distributed instances start my distributed algorithm synchronously. Furthermore, it solves the problem that some hazelcast members are not found, see https://stackoverflow.com/a/20716919/750378.

So how do I avoid both problems when running on a single machine? It would be great if the cluster size would simple be the number of running hazelcast instances. Then I could keep my configuration above no matter how I deploy my two instances (on 1 or 2 machines).

Update

I have posted an issue about the cluster size at https://github.com/hazelcast/hazelcast/issues/2292.

Answer 1

You could use the same machine to run multiples Hazelcast instance. Under the hoods, Hazelcast binds differents ports for each instance.

Following, a simple test with two instances:

HazelcastInstance firstInstance = Hazelcast.newHazelcastInstance(new Config());
HazelcastInstance secondInstance = Hazelcast.newHazelcastInstance(new Config());

// Introducing a sample data in a map using the first instance
firstInstance.getMap("TEST_MAP").put("key", "test_value");

// Prints the value using the second instance. The result will be 'test_value'
System.out.println(secondInstance.getMap("TEST_MAP").get("key"));

When this code starts the console output is:

Members [2] {
    Member [192.168.216.1]:5702
    Member [192.168.216.1]:5703 this
}

As you can see, two instances were registered in the same IP but different ports.