Understanding Server Load Balancing

Installing and Configuring Software for Load-Balancing Servers

At this point you have planned your cluster and created metadata for your servers and spawners. In this last stage, you will install and configure the server and spawner software on the hosts of your cluster, copy and edit server configuration files, and then start or refresh your spawners or OLAP servers.

Install Server and Spawner Software

The last stage in the process of creating a load-balancing cluster involves the installation of server and spawner software on the hosts of your cluster, and the copying and editing of server configuration files onto your hosts.

To install server software and configuration files on your hosts, follow these steps:

Use the SAS Deployment Wizard in Install Only mode to install the server software on the first new host in your cluster. Use Install Only mode so that you do not install server configuration, start-up, or log files. Instead of installing those files automatically, you will add and edit the configuration files manually, later in this procedure. For now, to install server software, see "Adding a New Server in an Existing Application Server" in the chapter "Managing SAS Application Servers."
For the same host, and for all server types other than OLAP (workspace, pooled workspace, or stored process), use the SAS Deployment Wizard to install an object spawner on the same host. Use Configuration Mode to automatically install spawner configuration files.
Copy all of the server start-up files from the logical server to the host that received the new server. Be sure to include the subdirectories named logs and sasuser, along with all of their contents. The path to the source files on the logical server should be of the form: SAS-config-dir/Levn/SASApp1/OLAPServerLB1/*.*. The path to the target on the new host should be of the form: SAS-config-dir/Levn/SASApp1/OLAPServerLB1/OLAPLB1_2249, where OLAPServerLB1_2249 is the name of the new server on the new host.
Edit the server files as described in the remainder of this section, according to the operating environment of each host, so that the files reflect the name and port of the new server.
Repeat these steps for the other hosts, servers, and spawners in your cluster.

Edit sasv9_usermods.cfg

SAS asks that you not edit sasv9.cfg. Instead, edit sasv9_usermods.cfg. The user modifications file serves the same purpose as sasv9.cfg, because the contents of the .cfg files are hierarchical and inherited.

To edit the file that was originally copied from the cluster's logical server, on each new host in your cluster, follow these steps:

In the -OBJECTSERVERPARMS option, change SERVER= to point to the new server.
Add the PORT= option to specify the unique port number for the new server.
In the Windows operating environment, add the PROTOCOL=BRIDGE option.
Change the -LOGCONFIGLOC option to point to the logconfig.xml file on the new server.
Change the -SASUSER option to point to the subdirectory of the same name on the new server.
Change the -CONFIG and -AUTOEXEC search paths. Give thought to the configuration settings and AUTOEXEC actions that you will share among the servers in your cluster. Add your settings and actions to the appropriate level of the search paths.

Edit logconfig.xml

To edit the log configuration file logconfig.xml, follow these steps:

For the Rolling File Appender, change the value of the fileNamePattern parameter to specify the location of the .log file on the new host.
For the ARM File Appender, change the value of fileNamePattern parameter to specify the location of the .arm file on the new host.

All logging behavior can be configured, as described in the SAS Intelligence Platform: System Administration Guide.

CAUTION:: For clusters of SAS OLAP Servers, SAS DATA Step Batch Servers, and SAS/CONNECT Servers, make sure that each server in your cluster writes to a separate ARM log file. Sharing log files results in inaccurate log information.

Edit the .bat File

On Windows, to edit the .bat file for your new server, follow these steps:

Change the value of CONFIGDIR= to include the name of the new server. Be sure not to change the application server context, which is commonly specified by %APPSERVER_ROOT%. The new server needs to point to the application server of the first server in the cluster, which runs on a different host.
Change the start command to include the name of the new server.

Edit shortcuts.ini

Files with names such as OLAPServer_shortcuts.ini might contain user-defined shortcuts. Update the server name in the paths that appear in this file.

Edit OLAPServerSSCU.ini and Install the Service

In the Windows operating environment, edit the server name that appears in various option values in this file. When the edits are complete, run the .bat file in install mode. For example, you might execute the following command:

C:\SAS\Config\Lev1\SASApp1\OLAP_LB1_2249\OLAPServer.bat install

Edits for the UNIX and z/OS Operating Environments

Edit the following configuration files in the UNIX operating environment, or in UNIX System Services for the z/OS operating environment: rexx.cfg, tkmvsenv.fg and the server shell file (with a name such as OLAPserver.sh). In all of these files you need to change the name of the server.

Start or Refresh the Object Spawners or OLAP Servers

You should now start or refresh the object spawners or OLAP servers in the load-balancing cluster. Refreshing a spawner reinitializes it. The spawners or OLAP servers reread their configuration out of the metadata. As part of this refresh, the spawner shuts down any servers that it currently has started. If changes are made to the server or spawner configurations, the spawner can be refreshed in order to pick up and apply these new changes. For more information, see "Refresh the Object Spawner" in the chapter "Managing SAS Application Servers".

At this point, your load balancing cluster should be operational. Check the log files as needed to confirm operation.

Top of Page