Re: Restart logging?

Mon, 07 Sep 2009 11:15:34 -0700
This of course works only in the case someone is using log4j and the PropertyConfigurator and nothing very exotic - which is of course what we're doing in the default installation... 


We could just output a log message that the log could not be reset in  
case it's something we don't know what it is.


/Janne

On 7 Sep 2009, at 14:55, Andrew Jaquith wrote:


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<[email protected]> 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:[email protected]]
Sent: maandag 7 september 2009 8:26
To: [email protected]
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<[email protected]> 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 <[email protected]>


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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