Chapter 11. The Logging Subsystem

11.1. Introduction

11.1.1. Overview of Logging

JBoss Enterprise Application Platform 6 provides highly configurable logging facilities for both its own internal use and for use by deployed applications. The logging subsystem is based on JBoss LogManager and it supports several third party application logging frameworks in addition to JBoss Logging.
The logging subsystem is configured using a system of log categories and log handlers. Log categories define what messages to capture, and log handlers define how to deal with those messages (write to disk, send to console etc).
All of this configuration can be performed in the Management Console or by using the CLI tool.

11.1.2. Application Logging Frameworks Supported By JBoss LogManager

JBoss LogManager supports the following logging frameworks:

11.1.3. Configure Boot Logging

The boot log is the record of events that occur while the server is starting up (or "booting").
The boot log can be configured by editing the logging.properties file. This file is a standard Java properties file and can be edited in a text editor. Each line in the file has the format of property=value.
Depending on whether you run the JBoss Enterprise Application Platform as a managed domain or standalone server, the full path to the logging.properties file is either EAP_HOME/domain/configuration/logging.properties or EAP_HOME/standalone/configuration/logging.properties.

11.1.4. Default Log File Locations

These are the log files that get created for the default logging configurations. The default configuration writes the server log files using periodic log handlers

Table 11.1. Default Log Files for a standalone server

Log File Description
EAP_HOME/standalone/log/boot.log
The server boot log. Contains log messages related to the startup of the server.
EAP_HOME/standalone/log/server.log
The Server Log. Contains all log messages once the server has launched.

Table 11.2. Default Log Files for a managed domain

Log File Description
EAP_HOME/domain/log/host-controller/boot.log
Host Controller boot log.Contains log messages related to the startup of the host controller.
EAP_HOME/domain/log/process-controller/boot.log
Process controller boot log. Contains log messages related to the startup of the process controller.
EAP_HOME/domain/servers/SERVERNAME/log/boot.log
Server Boot log for the named server. Contains log messages related to the startup of the specified server.
EAP_HOME/domain/servers/SERVERNAME/log/server.log
The server log for the named server. Contains all log messages for that server once it has launched.

11.1.5. About Log Levels

Log levels are an ordered set of enumerated values that indicate the nature and severity of a log message. The level of a given log message is specified by the developer using the appropriate methods of their chosen logging framework to send the message.
JBoss Enterprise Application Platform 6 supports all the log levels used by the supported application logging frameworks. The most commonly used six log levels are (in order of lowest to highest): TRACE, DEBUG, INFO, WARN, ERROR and FATAL.
Log levels are used by log categories and handlers to limit the messages they are responsible for. Each log level has an assigned numeric value which indicates its order relative to other log levels. Log categories and handlers are assigned a log level and they only process log messages of that level or higher. For example a log handler with the level of WARN will only record messages of the levels WARN, ERROR and FATAL.

11.1.6. Supported Log Levels

Table 11.3. Supported Log Levels

Log Level Value Description
FINEST 300
-
FINER 400
-
TRACE 400
Use for messages that provide detailed information about the running state of an application. Log messages of TRACE are usually only captured when debugging an application.
DEBUG 500
Use for messages that indicate the progress individual requests or activities of an application. Log messages of DEBUG are usually only captured when debugging an application.
FINE 500
-
CONFIG 700
-
INFO 800
Use for messages that indicate the overall progress of the application. Often used for application startup, shutdown and other major lifecycle events.
WARN 900
Use to indicate a situation that is not in error but is not considered ideal. May indicate circumstances that may lead to errors in the future.
WARNING 900
-
ERROR 1000
Use to indicate an error that has occurred that could prevent the current activity or request from completing but will not prevent the application from running.
FATAL 1100
Use to indicate events that could cause critical service failure and application shutdown and possibly cause JBoss Enterprise Application Platform 6 to shutdown.

11.1.7. About Log Categories

Log categories define a set of log messages to capture and one or more log handlers which will process the messages.
The log messages to capture are defined by their Java package of origin and log level. Messages from classes in that package and of that log level or lower are captured by the log category and sent to the specified log handlers.
Log categories can optionally use the log handlers of the root logger instead of their own handlers.

11.1.8. About the Root Logger

The root logger captures all log messages sent to the server (of a specified level) that are not captured by a log category. These messages are then sent to one or more log handlers.
By default the root logger is configured to use a console and a periodic log handler. The periodic log handler is configured to write to the file server.log. This file is sometimes referred to as the server log.

11.1.9. About Log Handlers

Log handlers define how captured log messages are recorded by JBoss Enterprise Application Platform. There are six types of log handler that can be configured: Console, File, Periodic, Size, Async and Custom.

11.1.10. Types of Log Handlers

Console
Console log handlers write log messages to either the host operating system’s standard out (stdout) or standard error (stderr) stream. These messages are displayed when JBoss Enterprise Application Platform 6 is run from a command line prompt. The messages from a Console log handler are not saved unless the operating system is configured to captured the standard out or standard error stream.
File
File log handlers are the simplest log handlers that write log messages to a specified file.
Periodic
Periodic file handlers write log messages to a named file until a specified period of time has elapsed. Once the time period has past then the file is renamed by appending the specified timestamp and the handler continues to write into a newly created log file with the original name.
Size
Size log handlers write log messages to a named file until the file reaches a specified size. When the file reaches a specified size, it is renamed with a numeric prefix and the handler continues to write into a newly created log file with the original name. Each size log handler must specify the maximum number of files to be kept in this fashion.
Async
Async log handlers are wrapper log handlers that provide asynchronous behaviour for one or more other log handlers. These are useful for log handlers that may have high latency or other performance problems such as writing a log file to a network file system.
Custom
Custom log handlers enable to you to configure new types of log handlers that have been implemented. A custom handler must be implemented as a Java class that extends java.util.logging.Handler and be contained in a module.

11.1.11. About Log Formatters

A log formatter is the configuration property of a log handler that defines the appearance of log messages from that handler. It is a string that uses a syntax based on java.util.Formatter class.
For example the log formatter string from the default configuration, %d{HH:mm:ss,SSS} %-5p [%c] (%t) %s%E%n , creates log messages that look like:
15:53:26,546 INFO  [org.jboss.as] (Controller Boot Thread) JBAS015951: Admin console listening on http://127.0.0.1:9990

11.1.12. Log Formatter Syntax

Table 11.4. Log Formatter Syntax

Symbol Description
%c The category of the logging event
%p The level of the log entry (info/debug/etc)
%P The localized level of the log entry
%d The current date/time (yyyy-MM-dd HH:mm:ss,SSS form)
%r The relative time (milliseconds since the log was initialised)
%z The time zone
%k A log resource key (used for localization of log messages)
%m The log message (including exception trace)
%s The simple log message (no exception trace)
%e The exception stack trace (no extended module information)
%E The exception stack trace (with extended module information)
%t The name of the current thread
%n A newline character
%C The class of the code calling the log method (slow)
%F The filename of the class calling the log method (slow)
%l The source location of the code calling the log method (slow)
%L The line number of the code calling the log method (slow)
%M The method of the code calling the log method (slow)
%x The Log4J Nested Diagnostic Context
%X The Log4J Message Diagnostic Context
%% A literal percent character (escaping)