Re: Restart logging?

[Andrew Jaquith]

Hi Janne --

A little experimentation with the live-install code suggests that  
Priha's RepositoryManager doesn't know how to un-cache its  
RepositoryImpl instances. Or to put it differently, there doesn't seem  
to be a way to reload or restart one.

Thoughts?

On Sep 7, 2009, at 13:04, Janne Jalkanen <janne.jalka...@ecyrd.com>  
wrote:


I'm not sure anybody thinks that slf4j was a bad idea :-).  I think  
Andrew's solution below is ok (though we might want to use  
Reflection to find the PropertyConfigurator).  It's good enough for  
first-use experience certainly, since we ship with log4j enabled by  
default. Besides, since Install.jsp only knows how to configure  
log4j, we don't need this functionality for anyone else either.

Also, I think some log libs know how to reload themselves if you  
change the config file.

/Janne

On 7 Sep 2009, at 21:55, Harry Metske wrote:

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.jaqu...@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.da...@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.jalka...@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.met...@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.jaqu...@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