2 Understanding WebLogic Logging Services

Components and Environment

There are two basic components in any logging system: a component that produces log messages and another component to distribute (publish) messages. WebLogic Server subsystems use a message catalog feature to produce messages and the Java Logging APIs to distribute them, by default. Developers can also use message catalogs for applications they develop.

The message catalog framework provides a set of utilities and APIs that your application can use to send its own set of messages to the WebLogic server log. The framework is ideal for applications that need to localize the language in their log messages, but even for those applications that do not need to localize, it provides a rich, flexible set of tools for communicating status and output.

See "Using Message Catalogs with WebLogic Server" in Oracle Fusion Middleware Using Logging Services for Application Logging for Oracle WebLogic Server.

In addition to using the message catalog framework, your application can use the weblogic.logging.NonCatalogLogger APIs to send messages to the WebLogic server log, for logging messages that do not need to be internationalized or are internationalized outside the WebLogic I18n framework. With NonCatalogLogger, instead of calling messages from a catalog, you place the message text directly in your application code.

See "Using the NonCatalogLogger APIs" in Oracle Fusion Middleware Using Logging Services for Application Logging for Oracle WebLogic Server.

To distribute messages, WebLogic Server supports Java based logging by default. The LoggingHelper class provides access to the java.util.logging.Logger object used for server logging. This lets developers take advantage of the Java Logging APIs to add custom handlers, filters, and formatters. See the Sun API documentation at http://java.sun.com/javase/6/docs/api/java/util/logging/package-summary.html.

Alternatively, you can configure WebLogic Server to use the Jakarta Project Log4j APIs to distribute log messages. See Log4j and the Commons Logging API.

Terminology

Logger - A Logger object logs messages for a specific subsystem or application component. WebLogic logging services use a single instance of java.util.logging.Logger for logging messages from the Message Catalogs, NonCatalogLogger, and the Debugging system.

Handler - A class that extends java.util.logging.Handler and receives log requests sent to a logger. Each Logger instance can be associated with a number of handlers to which it dispatches log messages. A handler attaches to a specific type of a log message; for example, the File Handler for the server log file.

Appender - An appender is Log4j terminology for a handler, in this case, an instance of a class that implements org.apache.log4j.Appender and is registered with an org.apache.log4j.Logger to receive log events.

Overview of the Logging Process

WebLogic Server subsystems or application code send log requests to Logger objects. These Logger objects allocate LogRecord objects which are passed to Handler objects for publication. Both loggers and handlers use severity levels and (optionally) filters to determine if they are interested in a particular LogRecord object. When it is necessary to publish a LogRecord object externally, a handler can (optionally) use a formatter to localize and format the log message before publishing it to an I/O stream.

Figure 2-1 shows the WebLogic Server logging process: WebLogic Catalog APIs or Commons Logging APIs are used for producing messages; Java Logging (default) and Log4j are options for distributing messages.

Figure 2-1 WebLogic Server Logging Process

Description of "Figure 2-1 WebLogic Server Logging Process"

Figure 2-1 illustrates the following process:

1. The client, in this case, a WebLogic Server subsystem or Java EE application, invokes a method on one of the generated Catalog Loggers or the Commons Logging implementation for WebLogic Server.

   1. When WebLogic Server message catalogs and the NonCatalogLogger generate messages, they distribute their messages to the server Logger object.

   2. The Jakarta Commons Logging APIs define a factory API to get a Logger reference which dispatches log requests to the server Logger object.

      The server Logger object can be an instance of java.util.logging.Logger or org.apache.log4j.Logger.

2. The server Logger object publishes the messages to any message handler that has subscribed to the Logger.

   For example, the Stdout Handler prints a formatted message to standard out and the File Handler writes formatted output to the server log file. The Domain Log Broadcaster sends log messages to the domain log, which resides on the Administration Server, and the JMX Log Broadcaster sends log messages to JMX listeners on remote clients.

Best Practices: Integrating Java Logging or Log4j with WebLogic Logging Services

Consider the following recommendations for using WebLogic logging services with Java Logging or Log4j:

• Use the Catalog and NonCatalog loggers or the Commons API for producing log messages for publishing by WebLogic logging services.

• Use a Java Logging or Log4j Logger reference for adding custom handlers, appenders, or filters to WebLogic logging services for publishing messages.

• If your application is configured for Java Logging or Log4j, in order to publish application events using WebLogic logging services, create a custom handler or appender that relays the application events to WebLogic logging services using the message catalogs or Commons API.

For more information, see How to Use Log4j with WebLogic Logging Services.

Server Log Files and Domain Log Files

Each WebLogic Server instance writes all messages from its subsystems and applications to a server log file that is located on the local host computer. By default, the server log file is located in the logs directory below the server instance root directory; for example, DOMAIN_NAME\servers\SERVER_NAME\logs\SERVER_NAME.log, where DOMAIN_NAME is the name of the directory in which you located the domain and SERVER_NAME is the name of the server.

In addition to writing messages to the server log file, each server instance forwards a subset of its messages to a domain-wide log file. By default, servers forward only messages of severity level NOTICE or higher. While you can modify the set of messages that are forwarded, servers can never forward messages of the DEBUG severity level. See "Forward messages to the domain log" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help.

The domain log file provides a central location from which to view the overall status of the domain. The domain log resides in the Administration Server logs directory. The default name and location for the domain log file is DOMAIN_NAME\servers\ADMIN_SERVER_NAME\logs\DOMAIN_NAME.log, where DOMAIN_NAME is the name of the directory in which you located the domain and ADMIN_SERVER_NAME is the name of the Administration Server. See "Change domain log file name and location" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help.

The timestamp for a record in the domain log is the timestamp of the server where the message originated. Log records in the domain log are not written in the order of their timestamps; the messages are written as soon as they arrive. It may happen that a Managed Server remains out of contact with the Administration Server for some period of time. In that case, the messages are buffered locally and sent to the Administration Server once the servers are reconnected.

How a Server Instance Forwards Messages to the Domain Log

To forward messages to the domain log, each server instance broadcasts its log messages. A server broadcasts all messages and message text except for messages of the DEBUG severity level.

The Administration Server listens for a subset of these messages and writes them to the domain log file. To listen for these messages, the Administration Server registers a listener with each Managed Server. By default, the listener includes a filter that allows only messages of severity level NOTICE and higher to be forwarded to the Administration Server. (See Figure 2-2.)

Figure 2-2 WebLogic Server and Domain Logs

Description of "Figure 2-2 WebLogic Server and Domain Logs"

For any given WebLogic Server instance, you can override the default filter and create a log filter that causes a different set of messages to be written to the domain log file. For information on setting up a log filter for a WebLogic Server instance, see "Create log filters" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help.

If the Administration Server is unavailable, Managed Servers continue to write messages to their local server log files. However, by default, when the servers are reconnected, not all the messages written during the disconnected period are forwarded to the domain log file. A Managed Server keeps a specified number of messages in a buffer so they can be forwarded to the Administration Server when the servers are reconnected.

The number of messages kept in the buffer is configured by the LogMBean attribute DomainLogBroadcasterBufferSize. DomainLogBroadcasterBufferSize controls the frequency with which log messages are sent from the managed server to the domain server. With the development default of 1, there is not batching of log messages; only the last logged message is forwarded to the Administration Server domain log. For example, if the Administration Server is unavailable for two hours and then is restored, the domain log will not contain any messages that were generated during the two hours. See "MSI Mode and the Domain Log File" in Oracle Fusion Middleware Managing Server Startup and Shutdown for Oracle WebLogic Server. In production mode, the default buffer size on the managed server is 10. When the buffer reaches its capacity, the messages in the buffer are flushed by sending them to the domain log on the administration server. For performance reasons, it is recommended that you set this value to 10 or higher in production. A higher value will cause the buffer to be broadcast to the domain log less frequently.

If you have configured a value greater than 1, that number of messages will be forwarded to the domain log when the Managed Server is reconnected to the Administration Server.

Server Log

The server log records information about events such as the startup and shutdown of servers, the deployment of new applications, or the failure of one or more subsystems. The messages include information about the time and date of the event as well as the ID of the user who initiated the event.

You can view and sort these server log messages to detect problems, track down the source of a fault, and track system performance. You can also create client applications that listen for these messages and respond automatically. For example, you can create an application that listens for messages indicating a failed subsystem and sends E-mail to a system administrator.

The server log file is located on the computer that hosts the server instance. Each server instance has its own server log file. By default, the server log file is located in the logs directory below the server instance root directory; for example, DOMAIN_NAME\servers\SERVER_NAME\logs\SERVER_NAME.log, where DOMAIN_NAME is the name of the directory in which you located the domain and SERVER_NAME is the name of the server. See "Change server log file name and location" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help.

To view messages in the server log file, you can log on to the WebLogic Server host computer and use a standard text editor, or you can log on to any computer and use the log file viewer in the Administration Console. See "View server logs" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help.

In addition to writing messages to a log file, each server instance prints a subset of its messages to standard out. Usually, standard out is the shell (command prompt) in which you are running the server instance. However, some operating systems enable you to redirect standard out to some other location. By default, a server instance prints only messages of a NOTICE severity level or higher to standard out. (A subsequent section, Message Severity describes severity levels.) You can modify the severity threshold so that the server prints more or fewer messages to standard out.

If you use the Node Manager to start a Managed Server, the messages that would otherwise be output to stdout or stderr when starting a Managed Server are instead displayed in the Administration Console and written to a single log file for that server instance, SERVER_NAME.out. The server instance's output log is located in the same logs directory, below the server instance root directory, along with the WebLogic Server SERVER_NAME.log file; for example, DOMAIN_NAME\servers\SERVER_NAME\logs\SERVER_NAME.out, where DOMAIN_NAME is the name of the directory in which you located the domain and SERVER_NAME is the name of the server.

The Node Manager writes its own startup and status messages to a single log file, NM_HOME/nodemanager.log, where NM_HOME designates the Node Manager installation directory, by default, WL_HOME/common/nodemanager.

For more information on Node Manager log files, see "Node Manager Configuration and Log Files" in Oracle Fusion Middleware Node Manager Administrator's Guide for Oracle WebLogic Server.

Subsystem Logs

The server log messages and log file communicate events and conditions that affect the operation of the server or the application. Some subsystems maintain additional log files to provide an audit of the subsystem's interactions under normal operating conditions. The following list describes each of the additional log files:

• The HTTP subsystem keeps a log of all HTTP transactions in a text file. The default location and rotation policy for HTTP access logs is the same as the server log. You can set the attributes that define the behavior of HTTP access logs for each server or for each virtual host that you define. See "Setting Up HTTP Access Logs" in Oracle Fusion Middleware Configuring Server Environments for Oracle WebLogic Server and "Enable and configure HTTP logs" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help.

• Each server has a transaction log which stores information about committed transactions coordinated by the server that may not have been completed. WebLogic Server uses the transaction log when recovering from system crashes or network failures. You cannot directly view the transaction log - the file is in a binary format.

  The Transaction Manager uses the default persistent store to store transaction log files. Using the Administration Console, you can change where the default store is located. See "Configure the default persistent store for Transaction Recovery Service migration" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help.

• The WebLogic Auditing provider records information from a number of security requests, which are determined internally by the WebLogic Security Framework. The WebLogic Auditing provider also records the event data associated with these security requests, and the outcome of the requests. Configuring an Auditing provider is optional. The default security realm (myrealm) does not have an Auditing provider configured. See "Configuring the WebLogic Auditing Provider" in Oracle Fusion Middleware Securing Oracle WebLogic Server.

  All auditing information recorded by the WebLogic Auditing provider is saved in WL_HOME\DOMAIN_NAME\servers\SERVER_NAME\logs\DefaultAuditRecorder.log. Although an Auditing provider is configured per security realm, each server writes auditing data to its own log file in the server directory.

• The JDBC subsystem records various events related to JDBC connections, including registering JDBC drivers and SQL exceptions. The events related to JDBC are now written to the server log, such as when connections are created or refreshed or when configuration changes are made to JDBC objects. See "Monitoring WebLogic JDBC Resources" in Oracle Fusion Middleware Configuring and Managing JDBC for Oracle WebLogic Server.

• JMS logging is enabled by default when you create a JMS server, however, you must specifically enable it on message destinations in the JMS modules targeted to this JMS server (or on the JMS template used by destinations).

  JMS server log files contain information on basic message life cycle events, such as message production, consumption, and removal. When a JMS destination hosting the subject message is configured with message logging enabled, then each of the basic message life cycle events will generate a message log event in the JMS message log file.

  The message log is located in the logs directory, below the server instance root directory, DOMAIN_NAME\servers\SERVER_NAME\logs\jmsServers\SERVER_NAMEJMSServer\jms.messages.log, where DOMAIN_NAME is the name of the directory in which you located the domain and SERVER_NAME is the name of the server.

  After you create a JMS server, you can change the default name of its log file, as well as configure criteria for moving (rotating) old log messages to a separate file. See "Configure topic message logging" in the Oracle Fusion Middleware Oracle WebLogic Server Administration Console Help and "Monitoring JMS Statistics and Managing Messages" in Oracle Fusion Middleware Configuring and Managing JMS for Oracle WebLogic Server.

Format of Output to Standard Out and Standard Error

When a WebLogic Server instance writes a message to standard out, the output does not include the #### prefix and does not include the Server Name, Machine Name, Thread ID, User ID, Transaction ID, Diagnostic Context ID, and Raw Time Value fields.

Here is an example of how the message from the previous section would be printed to standard out:

<Sept 22, 2004 10:51:10 AM EST> <Notice> <WebLogicServer> <BEA-000360> <Server started in RUNNING mode>

In this example, the message attributes are: Locale-formatted Timestamp, Severity, Subsystem, Message ID, and Message Text.