Configure a Kaazing Gateway Cluster

To create a cluster, you must configure multiple gateways to communicate with each other. This is accomplished by adding a cluster service to each Gateway. Once a cluster service is configured on each Gateway cluster member and the members are started, the clustered instances will handle connection-switching when another cluster member unexpectedly terminates. Cluster members share information about activity and which of their services are load balanced.

In the following procedure, two Gateway members are clustered. Additional members can be added or removed using the same steps.

Before You Begin

This procedure is part of Configure the Gateway for High Availability:

  1. Using the Gateway to Support High Availability
  2. Configure a Kaazing Gateway Cluster
  3. Set Up Kaazing Gateway as a Load Balancer
  4. Troubleshoot Kaazing Gateway Clusters and Load Balancing

To Create a Cluster with the Gateway

In this example, there are two Gateways. Each Gateway is listening on its IP address for incoming connections ( for the first Gateway and for the second Gateway), and both are connecting to the cluster group address udp://

  1. On the first Gateway (, add the following cluster configuration element in the Gateway configuration file (GATEWAY_HOME/conf/gateway-config.xml).


    The cluster element requires name, accept, and connect elements:

    • The name element can be any name. The name must be the same in the cluster service of every Gateway that wishes to join this cluster.
    • The accept element contains the URI on which the cluster member listens for other cluster members. The URI contains the local IP address of the member. If the Gateway cannot match the IP address in the accept URI to one of the host’s network interfaces, then the cluster startup process will fail.
      The URI in the accept uses a TCP scheme followed by the IP address of the network interface for the connection, and a port number (the port number in this example is arbitrary).
    • The connect element contains the URI used to discover other cluster members. The cluster element can contain a single connect that uses a multicast address (such as udp:// or multiple connect elements that use unicast addresses (such as tcp://
      • For multicast addressing, the connect element URI is known as the group address. This URI must be the same in the cluster service of every Gateway that wishes to join this cluster. The connect element URI uses a multicast address and port number (the port number in this example is a common multicast port number). Each cluster member sends multicast datagrams to the multicast address. The connect element may use a hostname instead of a multicast address, such as udp://, if the hostname resolves in DNS to the IP addresses of all of the cluster members.
      • For unicast addressing, there can be many connect elements, each pointing to a different cluster member. The cluster service does not require a connect URI for every other cluster member. The minimum requirement is that a cluster service have a connect for one other cluster member in order to join the cluster.
  2. On the second Gateway (, add the following cluster service element (note that its name and connect elements are identical to those in the cluster service on the first Gateway).


    Notice that this accept element in the second Gateway uses the same port number as the accept element in the first Gateway. These are different hosts and can therefore use the same port number. This also simplifies administration.

  3. Start both cluster members.
  4. When you shut down one of the instances, you should see the following message in the terminal that was used to start the remaining gateway instance:

    INFO Cluster member / is down
Note: For TCP and UDP URLs in accept, tcp.bind, udp.bind, and protocol.transport elements, you can use the name of a network interface in place of a hostname or IP address. For example, <accept>tcp://@eth0:8123</accept> (Linux/Mac) and <tcp.bind>[@Local Area Connection]:8123</tcp.bind> (Windows). Use square brackets around a subinterface name or when the name contains spaces (<tcp.bind>[@eth0:1]:8123</tcp.bind>). Binding to an interface binds to all IP addresses defined on that interface (IPv4, IPv6).

By using interface names instead of IP address, the Gateway configuration file, gateway-config.xml, can be copied between Gateway cluster members without the need to update each cluster member’s configuration with its IP address.

Next Step

Set Up Kaazing Gateway as a Load Balancer



In this document, you learned about configuring the Gateway for clustering. For more information about Gateway administration, see the documentation.