Hi George, Comments inline. On 19.04.2012 16:15, George C. Hawkins wrote:
Hallo --
We have a system where we have what I'll call groups.
Each group has a numeric identifier and when a new group is created a corresponding large set of heterogeneous objects are created.
These objects are not shared between groups.
Whenever any of these objects log anything we always want to see the numeric identifier (of the group to which they belong) in the log message.
I take the above statement as the specification for what you wish to achieve. [cut]
logger.error("limit exceeded", groupId.args());
I'm inclined to think using Markers would be better. I would create a Marker instance in every class where I also had a logger, and initialize it such that its name would return something like "groupId=" + groupId.
However comments like the following on stackoverflow suggest this is an inappropriate use of Markers:
http://stackoverflow.com/a/4167298/245602
At the moment though I think I'll ignore this and uses Markers unless someone can suggest a better approach?
You could use markers. However, once a marker is created it lives until the app stops. To get around this problem you could create "detached" markers. See the getDetachedMarkers() method in in MarkerFactory. Instead of markers, I would suggest writing a conversion specifier [1], with conversion word %groupID and converter GroupIDConverter. Given that converters have access to all fields of the ILoggingEvent, including the parameters, GroupIDConverter could output the group id in the presence of a parameter of type GroupID. class MyObject { Logger logger = LoggerFactory.getLogger(MyObject.class); public GroupID getGroupId() { return ...; } void foo() { logger.info("Doing foo", getGroupId()); } } The trick here is to pass myObject's groupId as a parameter but have no corresponding anchor point, i.e. there is no '{}' in "Doing foo". You could factor the code so that objects with groupIds log by emitting their groupId as the last parameter (with no corresponding '{}'). HTH, [1] http://logback.qos.ch/manual/layouts.html#customConversionSpecifier
Regards,
/George
-- Ceki http://twitter.com/#!/ceki