Reference Manual 3.9-SNAPSHOT

Setting Up Clusters Other Network Configurations

All network related configurations are performed via the network element in the Hazelcast XML configuration file or the class NetworkConfig when using programmatic configuration. Following subsections describe the available configurations that you can perform under the network element.

Public Address

public-address overrides the public address of a member. By default, a member selects its socket address as its public address. But behind a network address translation (NAT), two endpoints (members) may not be able to see/access each other. If both members set their public addresses to their defined addresses on NAT, then that way they can communicate with each other. In this case, their public addresses are not an address of a local network interface but a virtual address defined by NAT. It is optional to set and useful when you have a private cloud. Note that, the value for this element should be given in the format host IP address:port number. See the following examples.

Declarative:

<network>
    <public-address>11.22.33.44:5555</public-address>
</network>

Programmatic:

Config config = new Config();
config.getNetworkConfig()
      .setPublicAddress( "11.22.33.44", "5555" );

Port

You can specify the ports that Hazelcast will use to communicate between cluster members. Its default value is 5701. The following are example configurations.

Declarative:

<network>
  <port port-count="20" auto-increment="false">5701</port>
</network>

Programmatic:

Config config = new Config();
config.getNetworkConfig().setPort( "5701" ); 
             .setPortCount( "20" ).setPortAutoIncrement( false );

port has the following attributes.

  • port-count: By default, Hazelcast will try 100 ports to bind. Meaning that, if you set the value of port as 5701, as members are joining to the cluster, Hazelcast tries to find ports between 5701 and 5801. You can choose to change the port count in the cases like having large instances on a single machine or willing to have only a few ports to be assigned. The parameter port-count is used for this purpose, whose default value is 100.

  • auto-increment: According to the above example, Hazelcast will try to find free ports between 5701 and 5801. Normally, you will not need to change this value, but it will come very handy when needed. You may also want to choose to use only one port. In that case, you can disable the auto-increment feature of port by setting auto-increment to false.

The parameter port-count is ignored when the above configuration is made.

Outbound Ports

By default, Hazelcast lets the system pick up an ephemeral port during socket bind operation. But security policies/firewalls may require you to restrict outbound ports to be used by Hazelcast-enabled applications. To fulfill this requirement, you can configure Hazelcast to use only defined outbound ports. The following are example configurations.

Declarative:

  <network>
    <outbound-ports>
      <!-- ports between 33000 and 35000 -->
      <ports>33000-35000</ports>
      <!-- comma separated ports -->
      <ports>37000,37001,37002,37003</ports> 
      <ports>38000,38500-38600</ports>
    </outbound-ports>
  </network>

Programmatic:

...
NetworkConfig networkConfig = config.getNetworkConfig();
// ports between 35000 and 35100
networkConfig.addOutboundPortDefinition("35000-35100");
// comma separated ports
networkConfig.addOutboundPortDefinition("36001, 36002, 36003");
networkConfig.addOutboundPort(37000);
networkConfig.addOutboundPort(37001);
...

Note: You can use port ranges and/or comma separated ports.

As shown in the programmatic configuration, you use the method addOutboundPort to add only one port. If you need to add a group of ports, then use the method addOutboundPortDefinition.

In the declarative configuration, the element ports can be used for both single and multiple port definitions.

Reuse Address

When you shutdown a cluster member, the server socket port will be in the TIME_WAIT state for the next couple of minutes. If you start the member right after shutting it down, you may not be able to bind it to the same port because it is in the TIME_WAIT state. If you set the reuse-address element to true, the TIME_WAIT state is ignored and you can bind the member to the same port again.

The following are example configurations.

Declarative:

  <network>
    <reuse-address>true</reuse-address>
  </network>

Programmatic:

...
NetworkConfig networkConfig = config.getNetworkConfig();

networkConfig.setReuseAddress( true );
...

Join

The join configuration element is used to discover Hazelcast members and enable them to form a cluster. Hazelcast provides multicast, TCP/IP, EC2, and jclouds® discovery mechanisms. These mechanisms are explained the Discovering Cluster Members section. This section describes all the sub-elements and attributes of join element. The following are example configurations.

Declarative:

   <network>
        <join>
            <multicast enabled="true">
                <multicast-group>224.2.2.3</multicast-group>
                <multicast-port>54327</multicast-port>
                <multicast-time-to-live>32</multicast-time-to-live>
                <multicast-timeout-seconds>2</multicast-timeout-seconds>
                <trusted-interfaces>
                   <interface>192.168.1.102</interface>
                </trusted-interfaces>   
            </multicast>
            <tcp-ip enabled="false">
                <required-member>192.168.1.104</required-member>
                <member>192.168.1.104</member>
                <members>192.168.1.105,192.168.1.106</members>
            </tcp-ip>
            <aws enabled="false">
                <access-key>my-access-key</access-key>
                <secret-key>my-secret-key</secret-key>
                <region>us-west-1</region>
                <host-header>ec2.amazonaws.com</host-header>
                <security-group-name>hazelcast-sg</security-group-name>
                <tag-key>type</tag-key>
                <tag-value>hz-members</tag-value>
            </aws>
            <discovery-strategies>
              <discovery-strategy ... />
            </discovery-strategies>
        </join>
   <network>

Programmatic:

Config config = new Config();
NetworkConfig network = config.getNetworkConfig();
JoinConfig join = network.getJoin();
join.getMulticastConfig().setEnabled( false )
            .addTrustedInterface( "192.168.1.102" );
join.getTcpIpConfig().addMember( "10.45.67.32" ).addMember( "10.45.67.100" )
            .setRequiredMember( "192.168.10.100" ).setEnabled( true );

The join element has the following sub-elements and attributes.

multicast element

The multicast element includes parameters to fine tune the multicast join mechanism.

  • enabled: Specifies whether the multicast discovery is enabled or not, true or false.
  • multicast-group: The multicast group IP address. Specify it when you want to create clusters within the same network. Values can be between 224.0.0.0 and 239.255.255.255. Default value is 224.2.2.3.
  • multicast-port: The multicast socket port that the Hazelcast member listens to and sends discovery messages through. Default value is 54327.
  • multicast-time-to-live: Time-to-live value for multicast packets sent out to control the scope of multicasts. See more information here.
  • multicast-timeout-seconds: Only when the members are starting up, this timeout (in seconds) specifies the period during which a member waits for a multicast response from another member. For example, if you set it as 60 seconds, each member will wait for 60 seconds until a leader member is selected. Its default value is 2 seconds.
  • trusted-interfaces: Includes IP addresses of trusted members. When a member wants to join to the cluster, its join request will be rejected if it is not a trusted member. You can give an IP addresses range using the wildcard (*) on the last digit of IP address, e.g., 192.168.1.* or 192.168.1.100-110.

tcp-ip element

The tcp-ip element includes parameters to fine tune the TCP/IP join mechanism.

  • enabled: Specifies whether the TCP/IP discovery is enabled or not. Values can be true or false.
  • required-member: IP address of the required member. Cluster will only formed if the member with this IP address is found.
  • member: IP address(es) of one or more well known members. Once members are connected to these well known ones, all member addresses will be communicated with each other. You can also give comma separated IP addresses using the members element.

imageNOTE: tcp-ip element also accepts the interface parameter. Please refer to the Interfaces element description below.

  • connection-timeout-seconds: Defines the connection timeout. This is the maximum amount of time Hazelcast is going to try to connect to a well known member before giving up. Setting it to a too low value could mean that a member is not able to connect to a cluster. Setting it to a too high value means that member startup could slow down because of longer timeouts, for example when a well known member is not up. Increasing this value is recommended if you have many IPs listed and the members cannot properly build up the cluster. Its default value is 5.

aws element

The aws element includes parameters to allow the members to form a cluster on the Amazon EC2 environment.

  • enabled: Specifies whether the EC2 discovery is enabled or not, true or false.
  • access-key, secret-key: Access and secret keys of your account on EC2.
  • region: The region where your members are running. Default value is us-east-1. You need to specify this if the region is other than the default one.
  • host-header: The URL that is the entry point for a web service. It is optional.
  • security-group-name: Name of the security group you specified at the EC2 management console. It is used to narrow the Hazelcast members to be within this group. It is optional.
  • tag-key, tag-value: To narrow the members in the cloud down to only Hazelcast members, you can set these parameters as the ones you specified in the EC2 console. They are optional.
  • connection-timeout-seconds: The maximum amount of time Hazelcast will try to connect to a well known member before giving up. Setting this value too low could mean that a member is not able to connect to a cluster. Setting the value too high means that member startup could slow down because of longer timeouts (for example, when a well known member is not up). Increasing this value is recommended if you have many IPs listed and the members cannot properly build up the cluster. Its default value is 5.

If you are using a cloud provider other than AWS, you can use the programmatic configuration to specify a TCP/IP cluster. The members will need to be retrieved from that provider, e.g., jclouds.

discovery-strategies element

The discovery-strategies element configures internal or external discovery strategies based on the Hazelcast Discovery SPI. For further information, please refer to the Discovery SPI section and the vendor documentation of the used discovery strategy.

AWSClient Configuration

To make sure EC2 instances are found correctly, you can use the AWSClient class. It determines the private IP addresses of EC2 instances to be connected. Give the AWSClient class the values for the parameters that you specified in the aws element, as shown below. You will see whether your EC2 instances are found.

public static void main( String[] args )throws Exception{ 
  AwsConfig config = new AwsConfig(); 
  config.setSecretKey( ... ) ;
  config.setSecretKey( ... );
  config.setRegion( ... );
  config.setSecurityGroupName( ... );
  config.setTagKey( ... );
  config.setTagValue( ... );
  config.setEnabled( true );
  AWSClient client = new AWSClient( config );
  List<String> ipAddresses = client.getPrivateIpAddresses();
  System.out.println( "addresses found:" + ipAddresses ); 
  for ( String ip: ipAddresses ) {
    System.out.println( ip ); 
  }
}

Interfaces

You can specify which network interfaces that Hazelcast should use. Servers mostly have more than one network interface, so you may want to list the valid IPs. Range characters ('*' and '-') can be used for simplicity. For instance, 10.3.10.* refers to IPs between 10.3.10.0 and 10.3.10.255. Interface 10.3.10.4-18 refers to IPs between 10.3.10.4 and 10.3.10.18 (4 and 18 included). If network interface configuration is enabled (it is disabled by default) and if Hazelcast cannot find an matching interface, then it will print a message on the console and will not start on that member.

The following are example configurations.

Declarative:

<hazelcast>
  ...
  <network>
    ...
    <interfaces enabled="true">
      <interface>10.3.16.*</interface> 
      <interface>10.3.10.4-18</interface> 
      <interface>192.168.1.3</interface>         
    </interfaces>    
  </network>
  ...
</hazelcast>

Programmatic:

Config config = new Config();
NetworkConfig network = config.getNetworkConfig();
InterfacesConfig interface = network.getInterfaces();
interface.setEnabled( true )
            .addInterface( "192.168.1.3" );

IPv6 Support

Hazelcast supports IPv6 addresses seamlessly (This support is switched off by default, please see the note at the end of this section).

All you need is to define IPv6 addresses or interfaces. The only current limitation is that you cannot define wildcard IPv6 addresses in the TCP/IP join configuration (tcp-ip element). Interfaces configuration does not have this limitation, you can configure wildcard IPv6 interfaces in the same way as IPv4 interfaces.

<hazelcast>
  ...
  <network>
    <port auto-increment="true">5701</port>
    <join>
      <multicast enabled="false">
        <multicast-group>FF02:0:0:0:0:0:0:1</multicast-group>
        <multicast-port>54327</multicast-port>
      </multicast>
      <tcp-ip enabled="true">
        <member>[fe80::223:6cff:fe93:7c7e]:5701</member>
        <interface>192.168.1.0-7</interface>
        <interface>192.168.1.*</interface>
        <interface>fe80:0:0:0:45c5:47ee:fe15:493a</interface>
      </tcp-ip>
    </join>
    <interfaces enabled="true">
      <interface>10.3.16.*</interface>
      <interface>10.3.10.4-18</interface>
      <interface>fe80:0:0:0:45c5:47ee:fe15:*</interface>
      <interface>fe80::223:6cff:fe93:0-5555</interface>
    </interfaces>
    ...
  </network>
  ...
</hazelcast>

JVM has two system properties for setting the preferred protocol stack (IPv4 or IPv6) as well as the preferred address family types (inet4 or inet6). On a dual stack machine, IPv6 stack is preferred by default, you can change this through the java.net.preferIPv4Stack=<true|false> system property. When querying name services, JVM prefers IPv4 addresses over IPv6 addresses and will return an IPv4 address if possible. You can change this through java.net.preferIPv6Addresses=<true|false> system property.

Also see additional details on IPv6 support in Java.

image NOTE: IPv6 support has been switched off by default, since some platforms have issues using the IPv6 stack. Some other platforms such as Amazon AWS have no support at all. To enable IPv6 support, just set configuration property hazelcast.prefer.ipv4.stack to false. Please refer to the System Properties section for details.