Define logging rules

Logging rules are defined separately for each part of the Alfabet functionality for which logging is provided. You can define different log levels for each functionality and different log targets. For each logging rule, you can define either one or multiple log targets, depending on your log infrastructure.

Define a default log level.

NLog uses a hierarchy of log levels. The levels are:

You can define which levels of log messages shall be used in the logging rules. NLog provides different methods for definition of log levels. In the Alfabet NLog example configuration files, specification of a minimum log level is used. If you specify, for example, a minimum log level of Error , only log levels with position 4 and higher in the hierarchy are written to the log file. You will see only Error and Fatal log messages. To ease change of the general log level, the Alfabet NLog example configuration files use a variable for the definition of the minimum log level:

• <variable name="log-level" value="Warn" />

In the rules, the minimum log level specification is specified via the variable:

• <logger name="alfabetlogger.UserLogon" minlevel="${var:log-level}" writeTo="file-all" final="true" />

To change the log level for all rules, you can change the value of the variable to the new log level and it will be automatically applied to all rules. If you want to change the log level for a single rule, you can delete the variable definition from the rule and overwrite it with the text specification of the log level.

Define logging rules.

Specify log details in the <rules> section of the NLog configuration file. Each functionality has a separate XML element <logger> with the following XML attributes:

• name: The functionality to be logged. A list of functionalities is given below.
• minlevel: The minimum position in the hierarchy of log levels considered in the log file. Log messages from lower positions are not creating any entry in the log. You can define the minlevel using the standard log level variables defined in the variable in the format minlevel="${var:log-level}"

  The levels are:

  Position	Log level	Description
  0	Trace	Most verbose level. Usually only activated for development.
  1	Debug	Debugging level including internal event logging.
  2	Info	Information level logging progress or application lifetime events.
  3	Warn	Warnings about validation issues or temporary failures are logged.
  4	Error	Erros where functionality has failed and exceptions are logged.
  5	Fatal	Most critical level. Log messages are only created when the application is about to abort.
  6	Off	No logging is done.

• writeTo: The name of the target of the log messages. You can define one target or multiple targets comma separated.
• final: If set to true , no other rules are executed after execution of this rule. As for most of the functionalities only one XML element <logger> is specified, this setting is used for all of them to end scanning for next rules.

For some of the loggers, filters are defined:

• For the alfabetlogger.System logger, two rules are defined, each having a filter. One rule implements logging to console during execution. The next rule blocks logging of .NET generated information to file.
• For the * logger, the re-execution of messages already covered by other loggers is suppressed.

The following loggers are available for Alfabet functionality.