NonStop Server Guide for BEA WebLogic Server 8.1

Using the WS Plug-in
HP NonStop Server Guide for BEA WebLogic Server 8.1—529891-001
8-4
Architecture
If that process is not available, the request is routed to an alternate target
application server process.
WebLogic Server application servers provide support for persisting session details.
This enables an alternate target application server process to restore it.
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If a cookie is not present, the WS Plug-in routes the request to the least busy
application server process.
Architecture
The WS Plug-in is implemented as a Pathway CGI server class. It interacts with other
iTP Secure WebServer components as follows:
1. If iTP Secure WebServer is configured to use traditional TCP/IP, the distributor
process receives a request from the network. The distributor process sends the
request to an HTTP Daemon process. If NonStop TCP/IPv6 is configured, the
HTTP Daemon processes all listen on the same port and NonStop TCP/IPv6
distributes requests to specific HTTP Daemon processes.
2. The HTTP Daemon process determines whether it can service the request. The
HTTP Daemon can service the request if the file specified by the pathname
component of the URL is present in the iTP Secure WebServer's file system or is
supported by a mapping to another iTP Secure WebServer component (for
example, NonStop Servlets for JavaServer Pages).
3. If the HTTP Daemon process can service the request, it does not invoke the WS
Plug-in (in which case, the rest of the steps do not apply). If the HTTP Daemon
process cannot service the request, it invokes the WS Plug-in, using the NonStop
TS/MP Pathsend facility.
4. The WS Plug-in uses an internal table (loaded at startup from an SQL table) to
identify the cluster that can handle the request. It reads an SQL table to obtain the
status information for the prefix specified. If the availability of the target application
server processes in the cluster that this path is configured to use have been
changed, the WS Plug-in also checks the cluster status table. This method
prevents the WS Plug-in from sending requests to a failed target application server
process.
5. The WS Plug-in attempts to connect to the best-performing server in the cluster. If
the best-performing server is not available, the WS Plug-in updates the status
tables and connects to the next-best server. Failed target application server
processes are retried periodically. The retry interval is configurable using the
RETRY_PERIOD option in the server class definition.