Hi Jason,
It makes sense only to index log messages that are written somewhere. Thus, it only
makes sense to peek at log events that are handled by an appender as those are the
only one that have a chance of being ever written. Many other messages are dropped by
the category instance because of the basic selection rule, i.e. the category instance
priority must be smaller or equal to the log statement priority.
My initial proposed solution is to attach a org.apache.log4j.spi.Filter that
consistently returned NEUTRAL but before returning performs Lucene indexing of the log
event. There are two problems with this approach:
1) If the Lucene filter is placed first in the filtering chain, then a later filter
can order to drop an indexed event. Thus, unwritten events are logged.
2) Filters have only access to org.apache.log4j.spi.LoggingEvent objects, not the
formatted event.
You might actually not be interested in the formatted event in that case there is one
easy solution: just sub-class the appender that you would like to index and override
it's subAppend method. As in
public class IndexedFileAppender extends FileAppender {
// When subAppend is called, we are assured that the
// event will be logged barring programming or hardware
// errors
void subAppender(LoggingEvent e) {
super.subAppend(e);
index(e); // do your Lucene indexing here
}
}
If you place the index invocation before super.subAppend you have preprocessing.
My main message here is that indexing is best done in the concerned appender. We can
either add pre-processing and post-processing support to *all* appenders or let the
appender handle indexing it self. I am more inclined for the latter solution mostly to
keep the log4j API as small as possible. Do other users want generalized pre- or
post-append processing? Regards, Ceki
At 23:06 11.03.2001 -0500, Jason van Zyl wrote:
>Hi,
>
>I was wondering if there was any sort of hook to process a log
>message before it is actually logged.
>
>I would like to index the log messages using Lucene so that
>the logs are searchable.
>
>Where is the best place to grab hold of the contents of
>a message before it is actually logged?
>
>I can do this myself by hacking around but maybe this
>pre-processing of log messages might be generally
>useful. Maybe I can already do this. Any pointers?
>
>Thanks,
>
>--
>jvz.
>
>Jason van Zyl
>[EMAIL PROTECTED]
>
>http://jakarta.apache.org/velocity
>http://jakarta.apache.org/turbine
>
>
>
>
>---------------------------------------------------------------------
>To unsubscribe, e-mail: [EMAIL PROTECTED]
>For additional commands, e-mail: [EMAIL PROTECTED]
I hope to see you at my ApacheCon 2001 presentation
entitled "Log4j, A Logging Package for Java".
See http://ApacheCon.Com/2001/US/ for more details.
----
Ceki Gülcü Web: http://qos.ch
av. de Rumine 5 email: [EMAIL PROTECTED] (preferred)
CH-1005 Lausanne [EMAIL PROTECTED]
Switzerland Tel: ++41 21 351 23 15
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
