OpenEdge Getting Started: Installation and Configuration - Product ...

Understanding server-level and connection-level fault tolerance
Understanding server-level and connection-level fault
tolerance
By default, a Unified Broker instance relies on a single controlling NameServer to
resolve client connection requests and a single Unified Broker instance to provide
services to the client. You can configure the controlling NameServer so that multiple
NameServer instances are available to resolve any client connection request, thus
providing connection-level fault tolerance. If your product supports load balancing, you
can also configure a single NameServer to resolve each connection request using
multiple Unified Broker instances that support the same Application Service, thus
providing server-level fault tolerance. Figure 9 shows the relationship between these
configuration options.
Client
Server -level
fault tolerance
Unified
Broker
instances
NameServer
instance
Client
Figure 9: Server-level and connection-level fault tolerance
These two levels of fault tolerance operate as follows:
Connection -level
fault tolerance
NameServer
instances
Unified
Broker
instance
• Server-level fault tolerance — Allows multiple Unified Broker instances to
register with a NameServer for the same Application Service. A client requesting
a connection is connected to one of several registered Unified Broker instances
that the NameServer determines are available to provide the specified Application
Service. If appropriate weight factors are specified, the NameServer also
balances connection load among the several broker instances. For more
information on load balancing, see the “Understanding load balancing” section on
page 491.
• Connection-level fault tolerance — Allows you to configure a collection of
NameServers that work together to resolve a client connection request. You can
use two different techniques, individually or together, to implement a fault-tolerant
NameServer collection. This section describes these techniques and assumes
that you are familiar with the documentation on using the NameServer with your
Unified Broker product.
You can apply server-level and connection-level fault tolerance individually or together
to achieve the level of fault tolerance that your application requires.
OpenEdge Getting Started: Installation and Configuration 493