Technical data

Configuring Multiple Middle-Tiers with a Load Balancing Router
4-6 Advanced Topologies for Enterprise Deployments
To understand how to configure OracleAS Portal with LBR, it is important to
understand the internal architecture of Portal:
■ The Parallel Page Engine (PPE) in Portal makes loopback connections to Oracle
Application Server Web Cache for requesting page metadata information. In a
default configuration, OracleAS Web Cache and the OracleAS Portal middle-tier
are on the same machine and the loopback is local. When Oracle Application
Server is front-ended by an LBR, all loopback requests from the PPE will start
contacting OracleAS Web Cache through the LBR. Assume that the OracleAS
Portal middle-tier and OracleAS Web Cache are on the same machine, or even on
the same subnet. Then, without additional configuration, loopback requests result
in network handshake issues during the socket connection calls.
■ In order for loopbacks to happen successfully, you must set up a Network Address
Translation (NAT) bounce back rule in the LBR, which essentially configures the
LBR as a proxy for requests coming to it from inside the firewall. This causes the
response to be sent back to the source address on the network, and then forwarded
back to the client.
■ OracleAS Portal leverages OracleAS Web Cache to cache a lot of its content. When
cached content in OracleAS Web Cache changes, OracleAS Portal sends Web
Cache invalidation requests from the database to OracleAS Web Cache. OracleAS
Portal can only send invalidation messages to one Web Cache node. In an
OracleAS Web Cache cluster, Portal relies on one OracleAS Web Cache member to
invalidate content in the other member of the cluster.
■ When Oracle Application Server is front-ended by an LBR, the LBR must be
configured to accept invalidation requests from the database and balance the load
among the cluster members.
Table 4–1 Additional information About the Graphic
Machine Details
Load balancing router Machine Name: lbr.abc.com
IP Address: L1.L1.L1.L1
Listening Port: 80
Invalidation Port: 4001 (accessible only from
inside)
Oracle Application Server (Portal
and Wireless middle-tier) 1
Machine Name: m1.abc.com
IP Address: M1.M1.M1.M1
Oracle HTTP Server Listening Port: 7778
OracleAS Web Cache Listening Port: 7777
OracleAS Web Cache Invalidation Port: 4001
Oracle Application Server (Portal
and Wireless middle-tier) 2
Machine Name: m2.abc.com
IP Address: M2.M2.M2.M2
Oracle HTTP Server Listening Port: 7778
OracleAS Web Cache Listening Port: 7777
OracleAS Web Cache Invalidation Port: 4001