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From Remko Popma <remko.po...@gmail.com>
Subject Re: looking for source
Date Sun, 06 Nov 2016 03:09:56 GMT
I will update the javadoc on the LogEvent interface to mention that Layouts and Appenders should
get the Throwable from the event and that the Message object may not be the instance initially
used in the Logger API to capture the message parameters and Throwable. 

Sent from my iPhone

> On 6 Nov 2016, at 11:16, Nicholas Duane <nickdu@msn.com> wrote:
> 
> Thanks, I'll check out the link you provided.
> 
> 
> I guess since log4j2 exposes:
> 
> 
> logger.error(String message);
> 
> 
> and
> 
> 
> logger.error(String message, Throwable t);
> 
> 
> As well as a bunch of others, I wasn't sure if it was the logging framework that did
the work of composing a single message out of the parameters to the call.  Otherwise you'll
get different behavior using different appender/layout, as we're seeing with our appender/layout.
> 
> 
> Thanks,
> 
> Nick
> 
> ________________________________
> From: Remko Popma <remko.popma@gmail.com>
> Sent: Saturday, November 5, 2016 10:03 PM
> To: Log4J Users List
> Subject: Re: looking for source
> 
> Nick,
> 
> If you want to combine the formatted message string and the stack trace into a single
string in your layout then yes, that is one way to do that.
> 
> For reference, take a look at the MessagePatternConverter and ThrowablePatternConverter
(used by Log4j's PatternLayout): https://github.com/apache/logging-log4j2/tree/master/log4j-core/src/main/java/org/apache/logging/log4j/core/pattern
> 
> Conceptually the Message and the Throwable are separate parts of the LogEvent. I think
what may have caused some confusion is that initially ParameterizedMessage captures message
parameters and the Throwable in a single vararg array, but please consider that an implementation
detail.
> 
> Sent from my iPhone
> 
>> On 6 Nov 2016, at 10:33, Nicholas Duane <nickdu@msn.com> wrote:
>> 
>> Thanks.  I have no problem doing that.  Just wondering what needs to be done and
how?  I guess I was hoping that the logging framework, eg. log4j, handled combining the message
and the exception such that no matter what appender/layout you used you'd get consistent results.
 Sounds like that's not the case.  So are you saying I need to combine the message and the
exception myself within our appender/layout?
>> 
>> 
>> From the code I included below you can see we're doing:
>> 
>> 
>> String message = logEvent.getMessage().getFormattedMessage();
>> 
>> 
>> to get the event's message.  Are you saying we should be doing something like this:
>> 
>> 
>> StringWriter sw = new StringWriter();
>> logEvent.getThrown().printStackTrace(new PrintWriter(sw));
>> String exceptionAsString = sw.toString();
>> String message = logEvent.getMessage().getFormattedMessage() + "\n" + exceptionAsString;
>> 
>> 
>> Thanks,
>> 
>> Nick
>> 
>> ________________________________
>> From: Remko Popma <remko.popma@gmail.com>
>> Sent: Saturday, November 5, 2016 9:16 PM
>> To: Log4J Users List
>> Subject: Re: looking for source
>> 
>> The point is that in a custom layout/appender you should get the throwable from the
LogEvent, not from the Message. That is the design that all Layouts and Appenders follow and
should follow.
>> 
>> The Message object passed to the Layout may no longer have the Throwable.
>> 
>> Sent from my iPhone
>> 
>>> On 6 Nov 2016, at 10:01, Nicholas Duane <nickdu@msn.com> wrote:
>>> 
>>> Thanks for the info.  Unfortunately I'm not following.  If someone can point
me to the source in question I will certainly look it over.  My sample outputs the message
(%msg) and when the method logger.error(String message, Throwable t) is called it seems some
code is combining the supplied string message with the exception message and stack trace.
 Just wondering what code is doing that as I'm told someone using our appender/layout is not
seeing the exception.
>>> 
>>> 
>>> Thanks,
>>> 
>>> Nick
>>> 
>>> ________________________________
>>> From: Remko Popma <remko.popma@gmail.com>
>>> Sent: Friday, November 4, 2016 9:58 PM
>>> To: Log4J Users List
>>> Subject: Re: looking for source
>>> 
>>> The Throwable is initially captured in the Message (usually ParameterizedMessage
or its garbage-free equivalent), but is later transferred to the LogEvent.
>>> 
>>> By the time the LogEvent reaches the Layout, the Message instance may be a different
Object than the one that originally held the Throwable.
>>> 
>>> The Layout should get the Throwable from the LogEvent, not from the Message.
>>> 
>>> Remko
>>> 
>>> Sent from my iPhone
>>> 
>>>> On 5 Nov 2016, at 7:50,Nicholas Duane <nickdu@msn.com> wrote:
>>>> 
>>>> Thanks for the replies.  Let me ask a more pointed question now as rummaging
through the source will probably take me hours.  I'm curious about the overloads with the
throwable, for instance:
>>>> 
>>>> 
>>>> logger.error("some message", <some throwable>);
>>>> 
>>>> 
>>>> What's the expected behavior?  Meaning, what is the logging framework going
to do with the message and the exception?  I know the message is usually output via the message
property in the pattern layout.  But what happens with the throwable?  Is there some code
responsible for constructing a message which combines the supplied message with the throwable
exception message and callstack?
>>>> 
>>>> 
>>>> I wrote the following simple java sample:
>>>> 
>>>> 
>>>> import org.apache.logging.log4j.Logger;
>>>> import org.apache.logging.log4j.LogManager;
>>>> 
>>>> public class Test
>>>> {
>>>> private static final Logger logger = LogManager.getLogger(Test.class);
>>>> 
>>>> public static void main(String[] args)
>>>> {
>>>>      logger.info("entered main");
>>>> try
>>>>         {
>>>>         throw(new IllegalArgumentException("bad argument"));
>>>>         }
>>>> catch(Throwable t)
>>>>         {
>>>>         logger.error("caught exception", t);
>>>>         }
>>>> logger.info("exiting main");
>>>> }
>>>> }
>>>> 
>>>> 
>>>> Here is the log4j2.xml file:
>>>> 
>>>> 
>>>> <?xml version="1.0" encoding="UTF-8"?>
>>>> <Configuration status="WARN">
>>>> <Appenders>
>>>>     <Console name="Console" >
>>>>         <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36}
\
>>>> - %msg%n"/>
>>>>     </Console>
>>>> </Appenders>
>>>> <Loggers>
>>>> <Root level="info">
>>>>         <AppenderRef ref="Console"/>
>>>> </Root>
>>>> </Loggers>
>>>> </Configuration>
>>>> 
>>>> 
>>>> Here is the output to the console when I run the sample:
>>>> 
>>>> 
>>>> [nick@thinkpad log4j]$ java Test
>>>> 16:37:57.681 [main] INFO  Test - entered main
>>>> 16:37:57.683 [main] ERROR Test - caught exception
>>>> java.lang.IllegalArgumentException: bad argument
>>>> at Test.main(Test.java:13) [log4j/:?]
>>>> 16:37:57.689 [main] INFO  Test - exiting main
>>>> 
>>>> 
>>>> So there does seem to be some code which is combining the message with the
exception.  Just wondering where that happens.  Now onto my specific problem.  We've got someone
saying that when they use the error() method which takes a string message and an throwable
the exception information is not making it to our central repository.  We have written our
own appender and our own layout.  Here is a snippet from our appender:
>>>> 
>>>> 
>>>> String serializedEvent = (String) getLayout().toSerializable(logEvent);
>>>> 
>>>> Here is a snippet from our layout:
>>>> 
>>>> 
>>>> String message = logEvent.getMessage().getFormattedMessage();
>>>> 
>>>> 
>>>> It seems the message above does not include any exception info.  What are
we doing wrong?
>>>> 
>>>> 
>>>> Thanks,
>>>> 
>>>> Nick
>>>> 
>>>> ________________________________
>>>> From: Remko Popma <remko.popma@gmail.com>
>>>> Sent: Friday, November 4, 2016 10:42 AM
>>>> To: Log4J Users List
>>>> Subject: Re: looking for source
>>>> 
>>>> Sure. Start in AbstractLogger in the API module: https://github.com/apache/logging-log4j2/blob/master/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java
> [https://avatars1.githubusercontent.com/u/47359?v=3&s=400]<https://github.com/apache/logging-log4j2/blob/master/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java>
> 
> apache/logging-log4j2<https://github.com/apache/logging-log4j2/blob/master/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java>
> github.com
> logging-log4j2 - Mirror of Apache Logging Log4J2
> 
> 
>> [https://avatars1.githubusercontent.com/u/47359?v=3&s=400]<https://github.com/apache/logging-log4j2/blob/master/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java>
>> 
>> apache/logging-log4j2<https://github.com/apache/logging-log4j2/blob/master/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java>
>> github.com
>> logging-log4j2 - Mirror of Apache Logging Log4J2
>> 
>> 
>>> [https://avatars1.githubusercontent.com/u/47359?v=3&s=400]<https://github.com/apache/logging-log4j2/blob/master/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java>
>>> 
>>> apache/logging-log4j2<https://github.com/apache/logging-log4j2/blob/master/log4j-api/src/main/java/org/apache/logging/log4j/spi/AbstractLogger.java>
>>> github.com
>>> logging-log4j2 - Mirror of Apache Logging Log4J2
>>> 
>>> 
>>>> 
>>>> and at some point you probably also want to look at the concrete subclass
Logger in the core module: https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/Logger.java
> [https://avatars1.githubusercontent.com/u/47359?v=3&s=400]<https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/Logger.java>
> 
> apache/logging-log4j2<https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/Logger.java>
> github.com
> logging-log4j2 - Mirror of Apache Logging Log4J2
> 
> 
>>> [https://avatars1.githubusercontent.com/u/47359?v=3&s=400]<https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/Logger.java>
>>> 
>>> apache/logging-log4j2<https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/Logger.java>
>>> github.com
>>> logging-log4j2 - Mirror of Apache Logging Log4J2
>>> 
>>> 
>>>> 
>>>> Hope this helps to get you started.
>>>> 
>>>> It may be easier to use an IDE and check out the whole project (https://logging.apache.org/log4j/2.x/source-repository.html).
> Log4j – Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
> logging.apache.org
> Access from Behind a Firewall. Refer to the documentation of the SCM used for more information
about access behind a firewall.
> 
> 
>> Log4j – Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
>> logging.apache.org
>> Access from Behind a Firewall. Refer to the documentation of the SCM used for more
information about access behind a firewall.
>> 
>> 
>>> Log4j - Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
>> Log4j – Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
>> logging.apache.org
>> Access from Behind a Firewall. Refer to the documentation of the SCM used for more
information about access behind a firewall.
>> 
>> 
>>> logging.apache.org
>>> Access from Behind a Firewall. Refer to the documentation of the SCM used for
more information about access behind a firewall.
>>> 
>>> 
>>>> Log4j - Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
>> Log4j – Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
>> logging.apache.org
>> Access from Behind a Firewall. Refer to the documentation of the SCM used for more
information about access behind a firewall.
>> 
>> 
>>> Log4j - Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
>> Log4j – Source Repository - Apache Log4j 2<https://logging.apache.org/log4j/2.x/source-repository.html>
>> logging.apache.org
>> Access from Behind a Firewall. Refer to the documentation of the SCM used for more
information about access behind a firewall.
>> 
>> 
>>> logging.apache.org
>>> Access from Behind a Firewall. Refer to the documentation of the SCM used for
more information about access behind a firewall.
>>> 
>>> 
>>>> logging.apache.org
>>>> Access from Behind a Firewall. Refer to the documentation of the SCM used
for more information about access behind a firewall.
>>>> 
>>>> 
>>>> 
>>>> Enjoy!
>>>> Remko
>>>> 
>>>> Sent from my iPhone
>>>> 
>>>>> On 4 Nov 2016, at 23:29, Nicholas Duane <nickdu@msn.com> wrote:
>>>>> 
>>>>> I'm not that familiar with java and java conventions, package names,
etc.  I'm trying to find the source for log4j2's implementation of logger.error(String, Throwable);.
 Can someone point me to that?  I was looking around here:
>>>>> 
>>>>> 
>>>>> https://git-wip-us.apache.org/repos/asf?p=logging-log4j2.git;a=tree;hb=refs/heads/master
>>>>> 
>>>>> 
>>>>> But couldn't seem to find what I was looking for.
>>>>> 
>>>>> 
>>>>> Thanks,
>>>>> 
>>>>> Nick
>>> 
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>>> 
>> 
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