log4j: Logging to same file from multiple contexts?

[David Filip]

Dear Tomcat Users,

Apologies if this is more of a log4j question, but I thought that I'd start here, in case Tomcat has any easy remedies.

I have a common webapp that I deploy to multiple, different contexts.

In log4j.properties, I have a few different log files defined, e.g., for logins:

log4j.appender.logins=org.apache.log4j.DailyRollingFileAppender
log4j.appender.logins.file=${catalina.home}/logs/logins.log
log4j.appender.logins.datePattern='.'yyyy-MM-dd
log4j.appender.logins.append=true
log4j.appender.logins.layout=org.apache.log4j.PatternLayout
log4j.appender.logins.layout.ConversionPattern=[%d{MM/dd/yyyy HH:mm:ss}] [%p] [%C{1}]: %m%n

log4j.logger.com.colornet.CAP.Actions.LoginAction=info, logins
log4j.logger.com.colornet.CAP.Util.LoginTokenTag=info, logins

However, as you may have guessed, if I have the same log4j configuration file for each context, the contexts tend to over-write each other.

Is there any way to have the SAME log4j.properties deployed too multiple contexts play nicely and not overwrite each other, but merely append each other?

Extra credit question (although sounds even more like a log4j question, so apologies): If not, is there any way to define the file path, e.g.:

log4j.appender.logins.file=${catalina.home}/logs/logins.log

to include the specific context? I have found a few references on the 'Net, e.g., ${contextPath}, ${servletName}, etc., which don't seem to work.

My goal (desire?) is to have the same webapp and configuration and web.xml and log4j.properties, etc., deployed to every web context, but not have one context overwrite another content's entries.

Of course, as the Mick once said, "You can't always have what you want".

Please let me know if this is possible.

Thanks,

Dave.

[Jäkel, Guido]

Dear Dave,

I walk through that years before, too.

Yes - you can't let write different Log4J Appenders to the same file or you get this garbage.

Yes - you have property resolving here, but there are no properties you need.


We did a solution using an additional servlet called at application init that temporary define a property from the application parameters like virtual host and context path, write out the first logging entry to let initialize Log4J here, i.e. read the configuration file with the current parameter and finally undefine the parameter (for savety). This sequence has to by synchronized by an JVM-wide singleton to prevent parallel execution in case you have more than one application using this. Write me an email if I should search for the source code.


Another solution is to use a SocketAppender and an "central" receiver anywhere (running with a standalone JVM)

<appender name="remote" class="org.apache.log4j.net.SocketAppender">
<param name="RemoteHost" value="${log4j.remotehost}" /> <-- this name is NOT related to log4j, you may choose any you want.
<param name="Port" value="${log4j.remoteport}" />
<param name="ReconnectionDelay" value="10" />
<param name="LocationInfo" value="false" />
</appender>


<appender name="async" class="org.apache.log4j.AsyncAppender">
<param name="BufferSize" value="4096" />
<param name="blocking" value="false" />
<param name="LocationInfo" value="false" />
<appender-ref ref="remote" />
</appender>

[...]

<root>
<level value="ERROR" />
<appender-ref ref="file" /> <-- local file logging
<appender-ref ref="async" />
</root>

The AsyncAppender is chained on top to have a fuse not to block logging (and the application) in case of trouble with the receiver.


Greetings

Guido

-----Original Message-----
Sent: Monday, October 08, 2018 8:28 PM
Subject: log4j: Logging to same file from multiple contexts?
Dear Tomcat Users,
Apologies if this is more of a log4j question, but I thought that I'd start here, in case Tomcat has any easy remedies.
I have a common webapp that I deploy to multiple, different contexts.
log4j.appender.logins=org.apache.log4j.DailyRollingFileAppender
log4j.appender.logins.file=${catalina.home}/logs/logins.log
log4j.appender.logins.datePattern='.'yyyy-MM-dd
log4j.appender.logins.append=true
log4j.appender.logins.layout=org.apache.log4j.PatternLayout
log4j.appender.logins.layout.ConversionPattern=[%d{MM/dd/yyyy HH:mm:ss}] [%p] [%C{1}]: %m%n
log4j.logger.com.colornet.CAP.Actions.LoginAction=info, logins
log4j.logger.com.colornet.CAP.Util.LoginTokenTag=info, logins
However, as you may have guessed, if I have the same log4j configuration file for each context, the contexts tend to over-write
each other.
Is there any way to have the SAME log4j.properties deployed too multiple contexts play nicely and not overwrite each other, but
merely append each other?
Extra credit question (although sounds even more like a log4j question, so apologies): If not, is there any way to define the
log4j.appender.logins.file=${catalina.home}/logs/logins.log
to include the specific context? I have found a few references on the 'Net, e.g., ${contextPath}, ${servletName}, etc., which
don't seem to work.
My goal (desire?) is to have the same webapp and configuration and web.xml and log4j.properties, etc., deployed to every web
context, but not have one context overwrite another content's entries.
Of course, as the Mick once said, "You can't always have what you want".
Please let me know if this is possible.
Thanks,
Dave.

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[Christopher Schultz]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

David,

Post by David Filip
Dear Tomcat Users,
Apologies if this is more of a log4j question, but I thought that
I'd start here, in case Tomcat has any easy remedies.
I have a common webapp that I deploy to multiple, different
contexts.
In log4j.properties, I have a few different log files defined,
log4j.appender.logins=org.apache.log4j.DailyRollingFileAppender
log4j.appender.logins.file=${catalina.home}/logs/logins.log
log4j.appender.logins.datePattern='.'yyyy-MM-dd
log4j.appender.logins.append=true
log4j.appender.logins.layout=org.apache.log4j.PatternLayout
log4j.appender.logins.layout.ConversionPattern=[%d{MM/dd/yyyy
HH:mm:ss}] [%p] [%C{1}]: %m%n
log4j.logger.com.colornet.CAP.Actions.LoginAction=info, logins
log4j.logger.com.colornet.CAP.Util.LoginTokenTag=info, logins
However, as you may have guessed, if I have the same log4j
configuration file for each context, the contexts tend to
over-write each other.
Is there any way to have the SAME log4j.properties deployed too
multiple contexts play nicely and not overwrite each other, but
merely append each other?
Extra credit question (although sounds even more like a log4j
question, so apologies): If not, is there any way to define the
log4j.appender.logins.file=${catalina.home}/logs/logins.log
to include the specific context? I have found a few references on
the 'Net, e.g., ${contextPath}, ${servletName}, etc., which don't
seem to work.
My goal (desire?) is to have the same webapp and configuration and
web.xml and log4j.properties, etc., deployed to every web context,
but not have one context overwrite another content's entries.
Of course, as the Mick once said, "You can't always have what you want".
Please let me know if this is possible.

I'm not sure it's really a great idea to have all these separate
context logging to the same log file(s), but here is a way to do this:

1. Move (*move!*) your log4j.jar file from WEB-INF/lib to Tomcat's
lib/ directory

2. Move (*move!) your log4j.properties file from WEB-INF/classes to
Tomcat's lib/ directory. You may have to wrap it in a JAR file.

This ought to allow log4j to initialize a single time, and each
application will use that singly-initialized log4j instance.

- -chris
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