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Application Migration and Development Guide
Migrating AppServer and WebSpeed Applications : ABL application code migration : Migrating client connections to PAS for OpenEdge : Using load balancing
Using load balancing
The classic AppServer can optionally rely on a NameServer that allows clients to locate AppServer instances by their application service name, thereby relieving the clients of needing to be configured with an explicit network address and port to access a particular AppServer instance. This same NameServer can achieve server fault tolerance and load balancing for a high client load by having access to multiple AppServer instances that provide the same application service to clients.
Since it is a Web application server, PAS for OpenEdge does not use the OpenEdge NameServer. It does allow the use of a DNS load balancing service and server-side proxies that allow a client to connect to a server resource without having to know the explicit network address and port, thus achieving a similar level of fault tolerance and load balancing using multiple PAS for OpenEdge instances that support the same OE ABL Web application. Examples of a DNS load balancer and server-side proxies include Apache Camel and the Apache HTTP Server with mod_proxy.
All OpenEdge clients must convert to connecting to a URL that identifies both the OE ABL Web application and connection transport supported by the PAS for OpenEdge instances registered with the DNS server. For PAS for OpenEdge REST and SOAP clients, the URL changes similar to the changes required when you move classic AppServer REST or WSA Adapters to a different Web server.
Note: For more information about load balancing configuration options for PAS for OpenEdge, see Progress Application Server for OpenEdge: Administration Guide.