About Logging

The Log4j 2 logging architecture provides a new approach to asynchronous logging. It uses asynchronous loggers, which submit log events to a work queue for later handling by the appropriate appenders.

More details can be found in the Log4j 2 async loggers documentation

Rhino offers support for mixed synchronous and asynchronous logging through logger configuration commands. Correctly configuring asynchronous logging has some complexity, discussed in how to Configure a Logger.

Rhino 2.6 introduces access to the Mapped Diagnostic Context (MDC) as a tool to tag and correlate log messages throughout an activity’s life cycle. This tagging can be combined with the new filters to allow very fine grained control of logging and tracing.

A simple SIP example of useful context would be including the P-charging-vector header. As this uniquely identifies a single call, it becomes trivial to identify all log messages related to handling an individual call. Identification (or filtering) remains simple even under load, with multiple calls handled in parallel.

The Logging Context Facility discusses MDC in greater detail.

Subsystems within the Rhino SLEE send log messages to specific loggers. For example, the rhino.facility.alarm logger periodically receives messages about which alarms are currently active within the Rhino SLEE.

Examples of logger names include:

Log levels can be assigned to individual loggers to filter how much information the SLEE produces:

Each log level will log all messages for that log level and above. For example, if a logger is set to the INFO level (the default), all of the log messages logged at the INFO, WARN, ERROR, and FATAL levels will be logged as well.

If a logger is not assigned a log level, it inherits its parent’s. For example, if the rhino.management logger has not been assigned a log level, it will have the same effective log level as the rhino logger.

The root logger is a special logger which is considered the parent of all other loggers. By default, the root logger is configured with the INFO log level. In this way, all other logger will output log messages at the INFO log level or above unless explicitly configured otherwise.

System administrators can use the console to create some simple log appenders. Full appender creation is available through the Rhino Element Manager (REM). These append log messages to destinations such as the console, a log file, socket, or Unix syslog daemon. At runtime, when Rhino logs a message (as permitted by the log level of the associated logger), Rhino sends the message to the log appender for writing. Types of log appenders include:

Filters can be applied to both loggers and appenders to restrict the set of log messages that are reported by a logger or through an appender. They provide a more flexible limiting approach than log level alone. Configuring filters can be performed using the Rhino Element Manager or by modifying an export of the logging configuration. A list of the filters available by default and their configuration properties can be found in the Log4j 2 filter documentation

An example filter configuration setting for limiting log levels to Finer in namespace volte and Info in all other namespaces is shown below:

If three trace messages are emitted by the service

With the service deployed in namespace volte only the Warning will be logged:

otherwise both the Finer and Warning messages will be logged:

The default threshold of Finer will cause the Finest message to never be logged.

Rhino contains several logging plugins to extend the functionality of Log4j 2 to aid SLEE management and provide additional context to logs.

Rhino log configuration variables include a rhino namespace containing options useful for providing additional context in log files. These are:

SLEE 1.1 provides tracer objects for logging messages from deployed components.

Rhino logs all messages sent to a Tracer under the trace.<notification source>.<tracer name> logger.

In an extension of the SLEE specification Rhino allows configuration of tracer levels at coarser grain than the component tracer. This extended functionality is accessed through the Rhino logging configuration. For example setloglevel trace Finest will set the default tracer level to Finest. All tracers not explicitly set will log at levels from Finest up. To support this SLEE extension root tracers for individual notification sources inherit their levels from the trace logger. It is also permitted to unset the root tracer level for a given notification source using setTracerLevel. Unsetting the root tracer level reverts to using the inherited level.

A further extension of the SLEE specification allows for full use of logging management commands against Tracers. A SLEE 1.1 Tracer may have appenders and filters added to further customise tracing output, both to JMX notifications, and logging destinations. Any supported appender may be used, so logging destinations are not restricted to file only.