UDP broadcasting supports NameServer replication by allowing a client or Unified Broker request to be received by multiple NameServers listening on the same UDP port and configured on different machines within the same subnet. Because every host on a subnet receives every broadcast request, one or more of these hosts can support a NameServer that receives and handles the same messages. This provides fault tolerance for both a client connection request and a Unified Broker registration request.
To configure and use replicated NameServers:
1. Run each NameServer instance on a separate host located within the same subnet.
2. Configure each NameServer instance to listen on the same UDP port.
3. Configure each client application to send its connection request and each Unified Broker to send its registration request using the subnet UDP broadcast address instead of the NameServer host address.
There is one broadcast address for each subnet. Using this address and the specified UDP port number, a client or Unified Broker sends a single request that is recognized by every NameServer listening on that port in the subnet.
The figure shows a client, a Unified Broker, and two replicated NameServers. The NameServer configurations shown for NameServer NS1 (above the dotted line) appear as they might in the ubroker.properties file for each host.
In the figure, one NameServer is located on a machine with the IP address 172.20.0.7 and another is located on a machine with the IP address 172.20.16.12. Both NameServers listen on UDP port 5162. The UDP broadcast address for these NameServers is 172.20.255.255. The Unified Broker is configured to register with a controlling NameServer remote from the Unified Broker machine using the UDP broadcast address 172.20.255.255 as the hostName. When the Unified Broker registers with its controlling NameServer using the UDP broadcast, it registers with both replicated NameServers. Similarly, when the client broadcasts its connection request using 172.20.255.255 as the NameServer host name, both replicated NameServers receive the request. The client uses the Unified Broker connection returned by the first NameServer that responds.
Note that if the NameServer at IP address 172.20.0.7 moves to a different host on the subnet, for example, with IP address 172.20.16.5, neither the client application nor the Unified Broker configuration has to change.
To configure and use NameServer replication:
1. Install the NameServer on each host within a single subnet where you want to replicate a NameServer configuration.
2. Configure each replicated NameServer to listen on the same UDP port number.
3. Determine the UDP broadcast address for the subnet where the NameServer hosts reside. For more information, see Determiningthe broadcast address.
4. Configure each Unified Broker instance (AppServer, SonicMQ Adapter Broker, WebSpeed Transaction Server, or DataServer) to use a controlling NameServer as follows:
Location — Remote
Port number — The UDP port number that you specified in Step 2
Host name — The UDP broadcast address that you determined from Step 3
5. Provide connection parameters to the client (AppServer, DataServer, or WebSpeed) that specify the required Application Service name, the broadcast address from Step 3, and the UDP port number that you specified in Step 2.
Location — Remote
