JRun Administrator's Guide
Logging

Introduction

During startup and while executing an application, JRun generates logging messages, such as server status, error conditions, and performance statistics. JSPs, servlets, and EJBs can generate logging messages, too. You can see these messages in the JRun log file.

You can configure JRun to handle different types of messages and to log these messages to different destinations. You can also create your own logging component to perform customized filtering and writing.

In general, JRun's logging mechanism requires little overhead, so it will have only a minimal effect on your application's performance.

Note:   Generating debug information affects the performance of an application; use this option only when debugging the application.

This chapter describes the logging mechanism, including the default logging configuration, instructions that let you modify that configuration, and examples that show you how to make those changes.

Types of messages

JRun generates the following types of messages:

• Informational messages, including messages generated during startup and method timing messages
• Warning messages
• Error messages
• Debug information
• Metrics about the system and the connection between a web server and JRun (see Chapter 7, "Connection Monitoring")

You can configure the logging mechanism to log one or more message types. Use the JMC to modify the message types that are logged.

Message destinations

The logging mechanism can send messages to these destinations:

• The log file
• The console screen

Logging components

JRun supplies the following logging components:

• Threaded logger  Use this logger as a central queue. The component creating the log message (JRun, servlet, JSP, or EJB) posts the message in an in-memory queue and regains control immediately. A background thread then processes the queue and send the log message to the appropriate log writers. This design helps maintain performance within your application.
• File writer  Receives a logging event and writes it to a file. By default, the threaded logger routes messages to the file writer.
• Console writer  Routes logging events to the system's standard output device, typically the screen.

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