Progress
Installation and Configuration Guide
Version 9
for UNIX
NameServers
A NameServer is a single process that mediates client connections for a set of Unified Brokers that have registered with it. Any number and type of Unified Broker instance can register with a single NameServer, and each Unified Broker instance can register with exactly one NameServer. The NameServer that a broker instance registers with is the broker’s controlling NameServer.
NOTE: The NameServer is an optional component that you can use to support these servers: Progress AppServer, SonicMQ Adapter, WebSpeed, and DataServer products. However, since Progress provides the NameServer by default, the information and graphics throughout this chapter assume you are using the NameServer. For specific information about the optional usage of the NameServer, see your product documentation.When a Unified Broker instance starts up, it registers with its controlling NameServer by sending its location and other configuration information to help resolve a connection request for the broker. Part of this registration information is the Application Service that the Unified Broker supports. An Application Service is a designation for the particular business function that a Unified Broker provides. For more information on Application Services, see the "Unified Broker" section.
NameServers provide the following services for a Unified Broker product:
- Location Transparency — A requesting client does not need to know the network location of a Unified Broker instance. When a client attempts to create a connection to a Unified Broker instance, it first requests the connection from a NameServer to a broker that provides a specified Application Service. The NameServer then locates and assigns a broker to complete the connection that provides the specified Application Service.
- Server-level Fault Tolerance and Load Balancing — If you have installed the load-balancing option, you can provide server-level fault tolerance, where the NameServer can select from several Unified Broker instances to satisfy a client request.This option also allows you to balance connection load among multiple Unified Broker instances that provide the same Application Service. The NameServer then assigns connections among several Unified Broker instances based on a weight factor that you configure for each instance. For more information on server-level fault tolerance, see the "Understanding Server-level and Connection-level Fault Tolerance" section. For more information on how load-balancing affects Unified Broker operation, see the "Understanding Load Balancing" section.
- Connection-level Fault Tolerance — You can also make multiple NameServer instances available to help ensure that at least one NameServer is available even if another fails. In this type of configuration, one of several possible NameServers resolves the connection request. Thus, you can provide connection-level fault tolerance for requesting clients. For more information on connection-level fault tolerance, see the "Understanding Server-level and Connection-level Fault Tolerance" section.
These NameServer services are available to the following servers: AppServer, WebSpeed Transaction Server, Sonic Adapter, and DataServer products. Also, all communications with the NameServer use User Datagram Protocol (UDP). The default configuration is to use the NameServer. However, the NameServer is an option feature. If you elect not to use NameServer for any of these servers, these features are not available.
For more information on how your Unified Broker product uses NameServers, see your product documentation.
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