Logging Quick Guide (SAP Library

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Logging Quick Guide

This Quick Guide gives an overview of:

● general rules for using the logging infrastructure

● preparation steps

● usage of logging and tracing

● configuration steps

● performance remarks

General Rules

● Bear in mind the difference between logs and traces. Logs are mainly addressed to an administrator of a customer system; traces – to a developer and support organization.

● An administrator is not interested in the details of the software architecture but in areas according to his/her administration tasks.

● A developer, however, wants to see the details of the software control flow. A log file can be a good starting point for error analysis done by support engineers.

● Logs are written to Categories, and traces – to Locations. Categories corresponds to administration tasks and are shared between different applications. Locations refer to certain points in the coding and can be identified with package-, class-, or function names.

● During normal operation, developers and support engineers are not looking on a running system. The administrator, however, has to check the system regularly. This implies that traces have not to be shown during normal operation, but logs do.

● For performance reasons, in the current J2EE configuration no traces are written during normal operation, but logs of severity INFO and higher are.

● Messages with severity DEBUG and PATH must be written as traces, not as log messages.

● Any error message (with severity ERROR or FATAL) is recommended to be written as a log message.

● Log files must have an extension .log, trace files – an extension .trc.

● Use always the exception framework as a basis to define your own exceptions.

Preparation Steps

Locations

Locations emits trace records. In every important class, create a reference to a Location, which corresponds to the fully qualified name of this class: private static final Location LOCATION = location.getLocation(Locking.class);

Use a static String object to hold the name of the method: String METHOD = “createLock(String)”;

Configuration Considerations

● The default severity setting for categories has to be INFO (so all log messages with severity INFO or higher will be written)

● The default severity setting for locations has to be ERROR.

Therefore, if you have exceptions, which you always want to trace, use the traceThrowableT method of the Location class.

● You can manually edit the log configuration XML file of your category or location and deploy it with libraries, interfaces, or applications. To deploy a logging configuration together with your component, you have to include the XML file into its corresponding archive. The name of the XML file must be "log-configuration.xml". It must follow a particular syntax.

For more information, see log-configuration.dtd.

Note

If the log-configuration.xml file is to be deployed with an application, it must be placed in the META-INF directory of the application's archive.

If it is to be deployed with a library or interface, it must be placed in the subdirectory called "dispatcher(or server)/descriptors". Whether the XML file will be in the "dispatcher/descriptors" only, or in the "server/descriptors" only, or in both directories, it depends on the cluster node the component is deployed to.

● You can use the SAP NetWeaver Developer Studio to add a log-configuration.xml file to your project and configure it during development.

For more information, see Log Configuration with SAP Netweaver Developer Studio.

● You can modify your logging configuration at runtime using the Visual Administrator.

For more information, see Logging Configuration Using the Visual Administrator.

Performance remarks

● If you have parameters, never build Strings yourself, always use the {n}-replacement

● If you have to make calculations for traces, check first if the tracing is active.

Then use the following: LOCATION.beLogged(severity)