Release 10.1A: OpenEdge Getting Started:
WebSpeed Essentials

NameServer

The NameServer serves as a hub through which a WebSpeed Messenger can locate a WebSpeed Transaction Server that provides the application services needed to fulfill a Web request. The NameServer provides location transparency that can ease deployment of your applications. The Enterprise version of the NameServer can also supply load balancing. Load balancing can improve performance and provide fault tolerance.

Understanding the NameServer’s load balancing option

Load balancing is a feature that allows client connection requests to be distributed, based on load, among multiple Unified broker instances that support the same Application Service. If you have installed the load-balancing option, the NameServer assigns client connections to the appropriate Unified broker instances based on weight factors that you specify.

If the weight factor that you specify for each Unified broker instance is appropriate in relation to the others, the effect is to assign more connections to broker instances with greater resources, and thus to balance connection load among all the instances. You can set the load-balancing weight factor for each Unified broker instance in the Progress Explorer or by editing the priorityWeight property in the ubroker.properties file.

Percentage weight factors

Properly specified, these weight factors give some sense of the amount of work that an individual WebSpeed Transaction Server instance can handle. For example, Table 2–3 shows the effect of weight factors specified for three WebSpeed Transaction Server instances registered for the same application service.

Table 2–3: Weight factors based on percentage 

WebSpeed Transaction Server name	Weight factor	% of time selected
WS1	20	20
WS2	20	20
WS3	60	60

The selection algorithm used by the NameServer guarantees that WS1 and WS2 are each selected 20% of the time and WS3 is selected 60% of the time. Thus, if the sum of weight factors for all WebSpeed Transaction Server instances that support the same application adds up to 100, each weight factor specifies the exact percentage of time that the NameServer selects the given WebSpeed Transaction Server instance over time.

Arbitrary weight factors

You can specify any sum of values (not necessarily 100), but the weight of each is always proportional to the sum, as shown in Table 2–4.

Table 2–4: Weight factors based on arbitrary sums 

WebSpeed Transaction Server name	Weight factor	% of time selected
WS1	2	2/7 = 28.57
WS2	2	2/7 = 28.57
WS3	3	3/7 = 42.86

Fail-over weight factor

Another use of Weight Factors is to provide connection-level fault tolerance by keeping a backup Transaction Server ready to take over the load if the other Transaction Servers in your network fail. If you assign a Weight Factor of zero to the backup Transaction Server, the NameServer does not select it to fill any of the incoming Web requests. If the NameServer loses connection with all the other Transaction Servers that support the application service, the NameServer directs all the Web requests to the backup Transaction Server.

For more information on load balancing and fault tolerance, see OpenEdge Getting Started: Installation and Configuration .

“No NameServer” configurations

While the NameServer can be useful, use of the NameServer is optional. There are several reasons why you might want to eliminate the NameServer from your configuration:

Simple configurations or low-demand deployments might not require location transparency and load balancing.
The NameServer uses the User Datagram Protocol (UDP). Some sites have restrictions that prohibit the use of UDP.

If you choose not to use the NameServer, configure your Transaction Server to indicate that it should not register with a NameServer. Then, configure your Messenger to connect directly to the Transaction Server. For more information, see the "Configuring a WebSpeed Transaction Server" section and the "Configuring a WebSpeed Messenger" section.

To eliminate the NameServer using Progress Explorer ():

Open your broker’s properties dialog box.
Select Controlling NameServer under the Broker node.
Deselect the Register With NameServer check box.
Choose OK.
Open your Messenger’s properties dialog box.
Select the Controlling NameServer node.
Deselect the Connect Using NameServer check box.
Type the hostname and port number of the broker.
Choose OK.

You can also eliminate the NameServer by directly editing the ubroker.properties file, although using Progress Explorer is less error-prone. For more information on Progress Explorer, see the "Progress Explorer" section. For more information on the ubroker.properties file, see the "ubroker.properties file" section.

To eliminate the NameServer by editing the ubroker.properties file:

Open install-dir/properties/ubroker.properties in a text editor.
Find the broker definition for your Transaction Server, for example:

[UBroker.WS.wsbroker1]

Note that wsbroker1 is the name of the Transaction Server.

Add and set the following property:

registerNameServer=0

Or, if registerNameServer is already set to 1, reset it to 0.

Find the definition for your Messenger. For example, if you use CGIIP:

[WebSpeed.Messengers.CGIIP]

Add and set the following property:

registerNameServer=0

Or, if registerNameServer is already set to 1, reset it to 0.

Add and set the port number for your broker. For example, if you are using the default wsbroker1:

Port=3055

Save and close the ubroker.properties file.
Note: When you eliminate the NameServer, the Messenger can only access one WebSpeed Transaction Server (broker). One of the advantages of using the NameServer is that you can run multiple brokers.