Sun Java System Application Server Enterprise Edition 8.1 2005Q2 High Availability Administration Guide

Monitoring the HTTP Load Balancer Plug-in

Configuring Log Messages

The load balancer plug-in uses the web server’s logging mechanism to write log messages. The default log level on the Application Server is set to the default logging level on Sun Java System Web Server (INFO), Apache Web Server (WARN) and Microsoft IIS (INFO). The application server log levels - FINE, FINER, and FINEST map to the DEBUG level on the web server.

These log messages are written to the web server log files, and are in the form of raw data that can be parsed using scripts, or imported into spreadsheets to calculate required metrics.

Types of Log Messages

The load balancer plug-in generates the following types of log messages:

Load Balancer Configurator Log Messages

These messages will be logged when you are using idempotent URLs and error page settings.

An output for idempotent URL pattern configuration contains the following information:

Request Dispatch and Runtime Log Messages

These log messages are generated while a request is being load balanced and dispatched.

Configurator Error Messages

These errors appear if there are configuration problems, for example, if the custom error page referenced is missing.

Enabling Load Balancer Logging

The load balancer plug-in logs the following information:

Note –

When load balancer logging is enabled, and if the web server logging level is set to DEBUG or to print verbose messages, the load balancer writes HTTP session IDs in the web server log files. Therefore, if the web server hosting the load balancer plug-in is in the DMZ, do not use the DEBUG or similar log level in production environments.

If you must use the DEBUG logging level, turn off load balancer logging by setting require-monitor-data property to false in loadbalancer.xml.

ProcedureTo turn on load balancer logging

  1. Set the logging options in the web server. The procedure depends on the web server:

    • With Sun Java System Web Server

      In the server’s admin console, go to the Magnus Editor tab and set the Log Verbose option to On.

    • For Apache Web Server, set the log level to DEBUG.

    • For Microsoft IIS, set the log level to FINE in the file.

  2. Set the load balancer configuration’s monitor option to true.

    Use the asadmin create-http-lb-config command to set monitoring to true when you initially create the load balancer configuration, or use the asadmin set command to set it to true later. Monitoring is disabled by default.

Understanding Monitoring Messages

The format of the load balancer plug-in log messages is as follows.