RE: How to have multiple loggers with shared code also using the logger?
Here's an update on the logger issue. It too me long to figure out because I
ran into an issue about privileged servlets and had to write my own
log4j.properties parser.
The original code posted earlier in this thread works in that it creates a
different logger for web application, and allows the user to stop and restart
the application.
public static Logger getLogger()
{
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
URL log4j_properties = classLoader.getResource(log4j_app.properties);
String loggerName = log4j_properties.toString(); // throws
NullPointerException if log4j_app.properties does not exist
synchronized (MyLog.class)
{
Logger logger =
Logger.getRootLogger().getLoggerRepository().exists(loggerName);
if (logger == null)
{
logger = Logger.getLogger(loggerName);
PropertyConfigurator.configure(log4j_properties);
System.out.println(Created logger: loggerName= + loggerName);
}
return logger;
}
}
One bug with the above is the line
PropertyConfigurator.configure(log4j_properties);
The above re-configures the root logger with the new log4j.properties, so
basically the new configuration applies to all loggers. What would be nice is
PropertyConfigurator.configure(logger, log4j_properties);
that configures only the specified logger with the log4j_properties.
Unfortunately, log4j does not have such a function, so I wrote my own (but it
only supports the properties used in my log4j_app.properties files).
Now, if web application 1 calls MyLog.getLogger() or calls common code that
calls MyLog.getLogger() then the first logger will be used, and similarly for
web application 2.
Finally, I create a servlet
import org.apache.catalina.manager.ManagerServlet;
public class TomcatManagerServlet extends ManagerServlet
The servlet is called for /reload, and it calls super.doGet() after doing
some checks.
It turns out that only privileged web applications can instantiate
ManagerServlet, so one has to have the following in context.xml:
Context privileged=true
I'm not sure what is the practical impact of setting privileged=true, though
the docs said something about the catalina and shared class loaders.
So upon calling
http://localhost/mywebservice/reload?path=/
the ROOT application is stopped and started. After the application restart,
all users are logged out and they have to log in again, but the logger
continues to work. A call to MyLog.getLogger() does not re-create the logger.
The logger is really owned by the common code in ${catalina.home}/lib. The
code
URL log4j_properties = classLoader.getResource(log4j_app.properties);
just gets the URL of the log4j.properties file. However, there is no pointer
to anything in the webapp, so it's possible to stop the webapp. And the line
PropertyConfigurator.configure(log4j_properties);
opens the URL (by calling log4j_properties.getInputStream()), reads it, and
closes it. So no stream in the webapp is open, and it's possible to stop the
webapp.
--- On Thu, 1/15/09, Caldarale, Charles R chuck.caldar...@unisys.com wrote:
From: Caldarale, Charles R chuck.caldar...@unisys.com
Subject: RE: How to have multiple loggers with shared code also using the
logger?
To: Tomcat Users List users@tomcat.apache.org
Date: Thursday, January 15, 2009, 11:28 AM
From: removeps-gro...@yahoo.com
[mailto:removeps-gro...@yahoo.com]
Subject: RE: How to have multiple loggers with shared
code
also using the logger?
How does one redploy a single application? Strange, I
could not find any information on this seemingly basic
task on google.
Read the real docs first, then Google only if needed.
http://tomcat.apache.org/tomcat-6.0-doc/deployer-howto.html#Deploying%20on%20a%20running%20Tomcat%20server
http://tomcat.apache.org/tomcat-6.0-doc/manager-howto.html
- Chuck
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RE: How to have multiple loggers with shared code also using the logger?
Thanks, this makes sense. However, I'd like to find out what is being held
onto by the log4j.jar. So I'd like to test it out. How does one redploy a
single application? Strange, I could not find any information on this
seemingly basic task on google. Thanks again.
--- On Wed, 1/14/09, Caldarale, Charles R chuck.caldar...@unisys.com wrote:
From: Caldarale, Charles R chuck.caldar...@unisys.com
Subject: RE: How to have multiple loggers with shared code also using the
logger?
To: Tomcat Users List users@tomcat.apache.org
Date: Wednesday, January 14, 2009, 9:27 PM
From: removeps-gro...@yahoo.com
[mailto:removeps-gro...@yahoo.com]
Subject: RE: How to have multiple loggers with shared
code
also using the logger?
And since the log4j.jar resides in the
${catalina.home}/lib
folder, this root logger is used by all web apps.
The log4j.jar is only there because you put it there. It
does not come with the Tomcat distribution, and it's
normally placed in the WEB-INF/lib directory of each webapp
that needs it.
By having such a jar in a common location, you've
pretty much guaranteed that you'll have to take Tomcat
down to redeploy a single webapp - the old webapp won't
go away because log4j will be hanging onto references to it.
(A common cause of PermGen filling up after redeployments.)
The servlet spec (and experience) strongly suggest that
webapps be kept as isolated as possible for this kind of
reason.
- Chuck
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OTHERWISE PROPRIETARY MATERIAL and is thus for use only by
the intended recipient. If you received this in error,
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RE: How to have multiple loggers with shared code also using the logger?
From: removeps-gro...@yahoo.com [mailto:removeps-gro...@yahoo.com] Subject: RE: How to have multiple loggers with shared code also using the logger? How does one redploy a single application? Strange, I could not find any information on this seemingly basic task on google. Read the real docs first, then Google only if needed. http://tomcat.apache.org/tomcat-6.0-doc/deployer-howto.html#Deploying%20on%20a%20running%20Tomcat%20server http://tomcat.apache.org/tomcat-6.0-doc/manager-howto.html - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
RE: How to have multiple loggers with shared code also using the logger?
Because of the classloading hierarchy. Once the logger is
initialized with the common classloader, everybody uses that
one.
Thanks. I studied the Apache logger code.
When we call org.apache.log4j.Logger.getLogger(), it calls functions of
LogManager. The static initializer block of LogManager gets log4j.properties
using the thread's class loader, so if the first webapp I run is mywebservice,
then it will get log4j.properties from mywebservice, such as
mywebservice/WEB-INF/classes/log4j.properties. The root logger will be
initialized using this log4j.properties file, and all new loggers will inherit
this configuration, which does not seem very useful.
And since the log4j.jar resides in the ${catalina.home}/lib folder, this root
logger is used by all web apps.
So what I did is
(1) Create a log4j.properties in ${catalina.home}/lib/log4j.properties or in a
jar file here.
(2) This properties file should contain the configuration shared by all app
loggers. For me, the file is one line:
log4j.rootLogger=warn
(3) Rename log4j.properties in each webapp and swingapp and JUnit test app to
log4j_app.properties.
(4) Modify MyLog.getLogger(), which is a function in a jar file that is shared
by all apps (ie. a function in ${catalina.home}/lib) so that when a logger is
created, initialize the logger from the appropriate log4j_app.properties.
import org.apache.log4j.PropertyConfigurator;
/**
* This function attempts to locate log4j_app.properties using the
* thread's classloader, and returns a logger using the location of
* log4j_app.properties as the logger name.
* The logger will be initialized with the configuration in
log4j_app.properties.
* This allows each application within the web server will use its own
logger.
* This function is thread-safe, and callers don't need to synchronized on
MyLog.
* @return
* @throws NullPointerException if log4j_app.properties does not exist
*/
public static Logger getLogger()
{
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
URL log4j_properties = classLoader.getResource(log4j_app.properties);
String loggerName = log4j_properties.toString();
synchronized (MyLog.class)
{
Logger logger =
Logger.getRootLogger().getLoggerRepository().exists(loggerName);
if (logger == null)
{
logger = Logger.getLogger(loggerName);
PropertyConfigurator.configure(log4j_properties);
System.out.println(Created logger: loggerName= + loggerName);
}
return logger;
}
}
Don't do that. Keep just one copy of the source
somewhere, just have your packaging script put the .class
file in the webapp package. No need to have an abstract
class or subclasses.
Not sure if that would work as the log4j.jar is in ${catalina.home}/lib, so the
root logger is shared by all apps.
(1) Pass a logger from the webapp to the common code
-- ie.
to add a Logger argument to all the functions in the
common
code, but this sounds tedious.
That's the cost of keeping things isolated, which is a
worthwhile goal.
(2) In each webapp have a filter that sets a thread
local
variable like ThreadLocalLogger threadLogger.
Just make sure you clear the ThreadLocal on *every*
possible exit path out of your request processing. If you
don't, you will have memory leaks in PermGen causing it
to fill up as webapps are redeployed.
-
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
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RE: How to have multiple loggers with shared code also using the logger?
From: removeps-gro...@yahoo.com [mailto:removeps-gro...@yahoo.com]
Subject: RE: How to have multiple loggers with shared code
also using the logger?
And since the log4j.jar resides in the ${catalina.home}/lib
folder, this root logger is used by all web apps.
The log4j.jar is only there because you put it there. It does not come with
the Tomcat distribution, and it's normally placed in the WEB-INF/lib directory
of each webapp that needs it.
By having such a jar in a common location, you've pretty much guaranteed that
you'll have to take Tomcat down to redeploy a single webapp - the old webapp
won't go away because log4j will be hanging onto references to it. (A common
cause of PermGen filling up after redeployments.)
The servlet spec (and experience) strongly suggest that webapps be kept as
isolated as possible for this kind of reason.
- Chuck
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
MATERIAL and is thus for use only by the intended recipient. If you received
this in error, please contact the sender and delete the e-mail and its
attachments from all computers.
-
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
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RE: How to have multiple loggers with shared code also using the logger?
-Original Message- From: removeps-gro...@yahoo.com [mailto:removeps-gro...@yahoo.com] How to have multiple loggers with shared code also using the logger? This is more of a log4j question that a Tomcat one. From a brief look at the log4j sources it looks as if you'll need a custom RepositorySelector that used the context classloader to select the repository to use. I thought log4j did that by default. I could be wrong on that or I might have read the source code incorrectly. Mark - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
RE: How to have multiple loggers with shared code also using the logger?
From: removeps-gro...@yahoo.com [mailto:removeps-gro...@yahoo.com]
Subject: How to have multiple loggers with shared code also
using the logger?
How to have multiple loggers with shared code also using the logger?
In ${catalina.home}/lib there is a jar file that contains class MyLog.
Doctor, doctor, it hurts when I do this.
The simple fix is: don't do it. Package your webapps so that each contains a
copy of MyLog rather than putting that class in the common location. You can
still maintain the same source, just make sure the .class file is located
locally in each webapp that uses it.
- Chuck
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
MATERIAL and is thus for use only by the intended recipient. If you received
this in error, please contact the sender and delete the e-mail and its
attachments from all computers.
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RE: How to have multiple loggers with shared code also using the logger?
Why is it what I'm trying to do not working though? It seems that my
MyLog.getLogger function does find the correct logger name, and that
Logger.getLogger() is always using the the first log4j.properties that was
found.
Yeah, I had tried something like this, namely to have a class AbstractMyLog in
the common folder, and a class MyLog in each of the webapps that derives from
AbstractMyLog so as to minimize code changes. But then the common code also
needs to write to the log file, and it should use the log file of the web
application that called it.
The other ideas I had are:
(1) Pass a logger from the webapp to the common code -- ie. to add a Logger
argument to all the functions in the common code, but this sounds tedious.
(2) In each webapp have a filter that sets a thread local variable like
ThreadLocalLogger threadLogger.
--- On Tue, 1/13/09, Caldarale, Charles R chuck.caldar...@unisys.com wrote:
From: Caldarale, Charles R chuck.caldar...@unisys.com
Subject: RE: How to have multiple loggers with shared code also using the
logger?
To: Tomcat Users List users@tomcat.apache.org
Date: Tuesday, January 13, 2009, 6:21 AM
From: removeps-gro...@yahoo.com
[mailto:removeps-gro...@yahoo.com]
Subject: How to have multiple loggers with shared code
also
using the logger?
How to have multiple loggers with shared code also
using the logger?
In ${catalina.home}/lib there is a jar file that
contains class MyLog.
Doctor, doctor, it hurts when I do this.
The simple fix is: don't do it. Package your webapps
so that each contains a copy of MyLog rather than putting
that class in the common location. You can still maintain
the same source, just make sure the .class file is located
locally in each webapp that uses it.
- Chuck
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR
OTHERWISE PROPRIETARY MATERIAL and is thus for use only by
the intended recipient. If you received this in error,
please contact the sender and delete the e-mail and its
attachments from all computers.
-
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
For additional commands, e-mail:
users-h...@tomcat.apache.org
-
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
For additional commands, e-mail: users-h...@tomcat.apache.org
RE: How to have multiple loggers with shared code also using the logger?
From: removeps-gro...@yahoo.com [mailto:removeps-gro...@yahoo.com] Subject: RE: How to have multiple loggers with shared code also using the logger? Why is it what I'm trying to do not working though? It seems that my MyLog.getLogger function does find the correct logger name, and that Logger.getLogger() is always using the the first log4j.properties that was found. Because of the classloading hierarchy. Once the logger is initialized with the common classloader, everybody uses that one. Yeah, I had tried something like this, namely to have a class AbstractMyLog in the common folder, and a class MyLog in each of the webapps that derives from AbstractMyLog so as to minimize code changes. Don't do that. Keep just one copy of the source somewhere, just have your packaging script put the .class file in the webapp package. No need to have an abstract class or subclasses. (1) Pass a logger from the webapp to the common code -- ie. to add a Logger argument to all the functions in the common code, but this sounds tedious. That's the cost of keeping things isolated, which is a worthwhile goal. (2) In each webapp have a filter that sets a thread local variable like ThreadLocalLogger threadLogger. Just make sure you clear the ThreadLocal on *every* possible exit path out of your request processing. If you don't, you will have memory leaks in PermGen causing it to fill up as webapps are redeployed. - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
