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From Harry Metske <harry.met...@gmail.com>
Subject Re: Restart logging?
Date Mon, 07 Sep 2009 18:55:20 GMT
Andrew,
see https://issues.apache.org/jira/browse/JSPWIKI-376

We have implemented slf4j to abstract away from specific logging
implementations.
PropertyConfigurator is a log4j specific class, if you would directly use
that class as coded below, you would revert all the effort done in
JSPWIKI-376 and we would rely again on log4j.
What you should at least do is first check if log4j is on the classpath and
then use reflection to get to the PropertyConfigurator. If there is no log4j
on the classpath we should disappoint the user by saying "sorry, no log4j
present, we can't do reconfigure logging right now".
LoggerFactory.registerLoggerMBean does a similar classpath-check/reflection
trick.
If we all think that slf4j abstraction wasn't a good idea because we have
thrown away all the log4j-specific goodies, we should get rid of slf4j
again, thereby reverting JSPWIKI-376. (vote ?)

A sort of meet in the middle might be to only change the log4j.properties
file, and require a webapp reload for the "logging restart" to work.

regards,
Harry

2009/9/7 Andrew Jaquith <andrew.r.jaquith@gmail.com>

> Ok, I figured it out. Google is my friend. I simply added this to the
> [new] WikiEngine.restart() method:
>
>        LogManager.resetConfiguration();
>        ClassLoader cl = this.getClass().getClassLoader();
>        URL log4jprops = cl.getResource( "log4j.properties" );
>        if (log4jprops != null)
>            PropertyConfigurator.configure(log4jprops);
>
> ...and that's all it took. I'll check this in soon.
>
> Hat-tip goes to Alan Green at bright-green.com. :)
>
> Now, this might not work if somebody swaps out their logging
> configuration, so we might want to add in some safeguards to see if
> Log4j is actually being used. But to Janne's point, this is about the
> first-use experience. Which has now improved dramatically. :)
>
> Andrew
>
> On Mon, Sep 7, 2009 at 5:43 AM, Dalen, Andre
> van<andre.van.dalen@siemens.com> wrote:
> >
> >> Another possibility is to switch to Simple logging, which always goes
> >
> >> to stdout - in Tomcat's case, catalina.out.  Then there would be no
> >> need to provide configuration on Install.jsp, which would simplify our
> >
> >> install process even more.
> >
> > Such simple logging would not give enough control on resource use.
> > It would be better imho to switch to log4j instead.
> >
> > Eventually a reload is shorthand for the sequence shutdown, startup.
> > Logging libraries should give their user control over when the shutdown
> > happens
> > exactly, so I would assume a reload won't be a problem if implemented
> > as a shutdown of the logging subsystem followed by a startup.
> >
> >        regards, Andre
> >
> > -----Original Message-----
> > From: Janne Jalkanen [mailto:janne.jalkanen@ecyrd.com]
> > Sent: maandag 7 september 2009 8:26
> > To: jspwiki-dev@incubator.apache.org
> > Subject: Re: Restart logging?
> >
> >
> > I don't think there's a simple way to do that through slf4j, simply
> > because log configuration is very specific to the actual logging
> > library used. For example, java.util.logging has a single global
> > LogManager, and to restart that one would mean writing our own
> > ClassLoader...
> >
> > However, since this is about first-use experience, it's unlikely that
> > someone would both be savvy enough to first switch the logging library
> > - THEN go and apply the easy-install process. So we might get away
> > simply by reconfiguring whichever logging library we happen to be
> > shipping with.
> >
> > Another possibility is to switch to Simple logging, which always goes
> > to stdout - in Tomcat's case, catalina.out.  Then there would be no
> > need to provide configuration on Install.jsp, which would simplify our
> > install process even more.
> >
> > /Janne
> >
> > On 7 Sep 2009, at 00:52, Andrew Jaquith wrote:
> >
> >> Hi Harry,
> >>
> >> The idea is to configure the wiki, including logging settings, using
> >> the installer screen. Then, after pressing the "Configure!" button,
> >> presto! the wiki is configured the way it should be without needing to
> >> restart the webapp. Instant gratification! It is much better than
> >> having to restart the webapp.
> >>
> >> Right now, in my local builds, everything *except* the log file change
> >> seems to work fine. The goal is to have the desired log file location
> >> (configured via the installer) reflected immediately -- the logs start
> >> going to that file. So I want to know how best to do that. Whether it
> >> is JMX or whatever, I don't care. But I am not a logging expert; hence
> >> the broadcast. If you have ideas I'd like to hear about them.
> >>
> >> Andrew
> >>
> >> On Sun, Sep 6, 2009 at 12:45 PM, Harry
> >> Metske<harry.metske@gmail.com> wrote:
> >>> Well,
> >>>
> >>> we have our own logging layer (org.apache.wiki.log) which talks to
> >>> slf4j
> >>> which talks to a real logging implementation (with log4j as the
> >>> default).
> >>> The first two don't have support for configuring logging at all,
> >>> the writer
> >>> of slf4j says you also shouldn't :
> >>> http://www.slf4j.org/faq.html#configure_logging
> >>> Log4j itself does support dynamic configuration of logging, but
> >>> that has
> >>> explicitly not been put in the slf4j interface.
> >>>
> >>> We do however have some way of dynamically configuring our loggers,
> >>> and
> >>> that's through the MBeans (currently you have to use jconsole to do
> >>> it, but
> >>> a nice GUI for it would still be nice). This is however limited.
> >>>
> >>> So with "restart logging" you could something in that direction,
> >>> but again,
> >>> that is limited to log4j, if you run another logging
> >>> implementation, you are
> >>> left alone in the dark.
> >>>
> >>> BTW, what exactly would be the difference between restarting the
> >>> engine and
> >>> reloading the whole webapp ?
> >>>
> >>> regards,
> >>> Harry
> >>>
> >>> 2009/9/6 Andrew Jaquith <andrew.r.jaquith@gmail.com>
> >>>
> >>>> Hi all --
> >>>>
> >>>> I am doing a bunch of work on the installer/config code. I've
> >>>> already
> >>>> got some really cool features implemented (LDAP config and live
> >>>> testing, Stripesification of the interface, configuration of
> >>>> multiple
> >>>> properties files simultaneously...). One thing I would REALLY like
> >>>> to
> >>>> do is to be able to apply changes to the wiki WITHOUT requiring a
> >>>> webapp reload.
> >>>>
> >>>> To that end, I wrote a restart() method for the WikiEngine, and it
> >>>> seems to work perfectly except in one respect: I can't figure out
> >>>> how
> >>>> to restart the logging subsystem. Any hints? I'd like to be able to
> >>>> allow the admin to specify the desired log file location, and after
> >>>> restart all of the logging is redirected there.
> >>>>
> >>>> Actually, there is one more thing: how does one set the Priha page
> >>>> directory? I'm pretty sure there's a setting in priha.properties
> >>>> that
> >>>> needs to be set, but I don't know what it is.
> >>>>
> >>>> Andrew
> >>>>
> >>>
> >
> >
>

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