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Migrating from log4j 1.2 to log4j2

I am in the process of migrating my application from log4j 1.2 to log4j2-2.8.1 version.
Following is the existing 1.x configuration in log4j.properties file.
log4j.appender.JSERRORFILE=org.apache.log4j.DailyRollingFileAppender
log4j.appender.JSERRORFILE.File=${log4j.loglocation}/jserror.log
log4j.appender.JSERRORFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.JSERRORFILE.layout.ConversionPattern=%d %-5p %c - %m%n
log4j.logger.com.app.JavascriptLogger=ERROR,JSERRORFILE
log4j.additivity.com.app.JavascriptLogger=false
Converted this to equivalent xml configuration log4j2.xml :
<RollingFile name="JSERRORFILE" fileName="${log-path}/jserror.log">
<PatternLayout pattern="%d %-5p %c - %m%n" />
</RollingFile>
<Logger name="com.app.JavascriptLogger" level="ERROR" additivity="false">
<AppenderRef ref="JSERRORFILE"/>
</Logger>
After conversion,I keep getting the following error :
org.apache.logging.log4j.core.config.ConfigurationException: Arguments given for element RollingFile are invalid
Any help would be appreciated.

You need to tell the RollingFile appender when to rollover (trigger policy) and what the result of a rollover should look like.
If you want to rollover at some regular interval (TimeBasedTriggeringPolicy or CronTriggeringPolicy) you need to specify a filePattern containing a SimpleDateFormat-like string. If you want to rollover to prevent large files (SizeBasedTriggeringPolicy), you need to specify a filePattern containing %i.
The filePattern is the relative or absolute path of the location you want the old (rolled over) file to be moved to.
Example:
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
<Appenders>
<RollingFile name="RollingFile" fileName="logs/app.log"
filePattern="logs/$${date:yyyy-MM}/app-%d{MM-dd-yyyy}-%i.log.gz">
<PatternLayout>
<Pattern>%d %p %c{1.} [%t] %m%n</Pattern>
</PatternLayout>
<Policies>
<CronTriggeringPolicy schedule="0 0 0 * * ?"/>
<SizeBasedTriggeringPolicy size="250 MB"/>
</Policies>
</RollingFile>
</Appenders>
<Loggers>
<Root level="error">
<AppenderRef ref="RollingFile"/>
</Root>
</Loggers>
</Configuration>
The cron expression above fires once a day.
For details and more examples see the RollingFile appender section of the user manual.

Archiving log file using log4j2 2.5

I have been trying to archive my application logs file which are older than a certain period. Noticed that since log4j 2.5 we have a Deletetag which let's you define the criteria based on which we can delete/archive our logs. Tried using this but I am somehow not able to crack it. Tried with a 30day 30d value and that isn't working on my server and neither is a 20 second policy PT20S working in my Dev Machine.
Any direction is greatly appreciated.
XML is as below:
<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
<Appenders>
<Console name="Console" target="SYSTEM_OUT">
<PatternLayout pattern="%d{yyyyMMdd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
</Console>
<RollingFile name="RollingFile" fileName="C://logs///test.log" filePattern="C://logs//test-%d{MM-dd-yyyy}.log.gz" ignoreExceptions="false">
<PatternLayout pattern="%d{yyyyMMdd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
<TimeBasedTriggeringPolicy />
<DefaultRolloverStrategy>
<Delete basePath="C://logs//" maxDepth="2">
<IfFileName glob="*/test-*.log.gz" />
<IfLastModified age="PT20S" />
</Delete>
</DefaultRolloverStrategy>
</RollingFile>
</Appenders>
<Loggers>
<Root level="INFO">
<AppenderRef ref="Console" />
<AppenderRef ref="RollingFile" />
</Root>
</Loggers>
</Configuration>

If you're using Windows the file and filePattern of the RollingFile appender can use single slashes. The double slashes may confuse it.
You can debug by setting <Configuration status="trace"> in the beginning of the configuration file.
Update:
The rolled over files end up in the c:/logs directory (filePattern="C://logs//test-%d{MM-dd-yyyy}.log.gz").
However, the Delete action is configured to only look at files ending in "log.gz" that are in subdirectories of c:/logs. Files in the c:/logs directory itself are not matched by glob="*/test-*.log.gz".
To fix this, use glob="test-*.log.gz".
It was mentioned in the comments that changing glob to regex also resolved the problem.

log4j2 prints new line between stdout

Why does log4j prints a new line break in stdout appender?
my log4j2.xml:
<?xml version="1.0" encoding="UTF-8"?>
<Configuration xmlns="http://logging.apache.org/log4j/2.0/config">
<Appenders>
<File name="FILE" fileName="<<FILEPATH>>\logfile.log"
append="true">
<PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} | %-5p | %l - %m%n" />
</File>
<File name="UIFILE" fileName="<<FILEPATH>>\uilogfile.log"
append="true">
<PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} | %m%n" />
</File>
<Console name="STDOUT" target="SYSTEM_OUT">
<PatternLayout>
<pattern>[%-5p] %C{2} - %m%n</pattern>
</PatternLayout>
</Console>
</Appenders>
<Loggers>
<Logger name="org.apache.log4j.xml" level="INFO"/>
<Logger name="com.foo" level="DEBUG" />
<Logger name="com.foo.services.web.controllers.FOOLoggingController"
level="INFO">
<AppenderRef ref="UIFILE" />
</Logger>
<Root>
<AppenderRef ref="STDOUT" />
<AppenderRef ref="FILE" />
</Root>
</Loggers>
</Configuration>
everything works fine but I get a new line between outputs, don't know why!
I tried few things like removing %n from the pattern layout but when i do this, the log itself stops coming. The file output is good. It doesn't prints new line in between. Has someone faced a similar issue?

I solved this issue by replacing %n with \n inside the Console's pattern string. So the Console appender would look like:
<Console name="STDOUT" target="SYSTEM_OUT">
<PatternLayout pattern ="[%-5p] %C{2} - %m \n" />
</Console>

Replacing with \n is not a good solution.
You should make sure if there is another logging framework wrapping your logs to standard output.
This happening in case of application servers, where deployed applications use a logging framework to send formatted messages to standard output, and server uses its own active logging framework to wrap the message around with its own format, before sending it to standard output.
This causes double formatting & therefore double newlines. Check your runtime, if there is an active logger wrapping your messages.

Time based triggering policy in log4j2

I am trying to create new log files on an hourly basis. I am using TimeBasedTriggerringPolicy of lo4j2 in RollingFileAppender. Below is the sample xml configuration code i have taken from log4j2 official site.
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
<Appenders>
<RollingFile name="RollingFile" fileName="logs/app.log" filePattern="logs/$${date:yyyy-MM}/app-%d{yyyy-MM-dd-HH}-%i.log.gz">
<PatternLayout>
<Pattern>%d %p %c{1.} [%t] %m%n</Pattern>
</PatternLayout>
<Policies>
**
<TimeBasedTriggeringPolicy interval="1" modulate="true" />
**
<SizeBasedTriggeringPolicy size="250 MB" />
</Policies>
</RollingFile>
</Appenders>
<Loggers>
<Root level="error">
<AppenderRef ref="RollingFile" />
</Root>
</Loggers>
</Configuration>
In the interval attribute I have set 1 which signifies 1 hour.
But still my file does not roll every 1 hour.
Please help me find any mistake.
Note : I have included beta9 of log4j2 (which is the latest)

1 here indicates 1 day and not 1 hour. I have manually tested with below configuration.
<RollingFile name="T" fileName="/data_test/log/abc.log"
filePattern="/data_test/log/abc-%d{MM-dd-yyyy}-%i.log">
<PatternLayout>
<Pattern>%d{ISO8601} %-5p [%t] (%F:%L) - %m%n</Pattern>
</PatternLayout>
<Policies>
<TimeBasedTriggeringPolicy interval="1" modulate="true"/>
<SizeBasedTriggeringPolicy size="100 KB" />
</Policies>
</RollingFile>
For manual testing, I change the system date and time.
First, try with increasing 1 hour. The log files will be generated but not as per the expectation.
Then change the system date, increase by 1 day and then see the results.
Suppose the last log file (abc.log) on day 29-Oct is of 50 KB. Configuration size is 100 KB. If we change the day (increase by 1 day) and then run.
Then, last file will be renamed 29-Oct-(some sequence number).log (50 KB file as it is copied) and new file will be created with abc.log
I have tried this with simple servlet with below configuration in web.xml
<context-param>
<param-name>log4jConfiguration</param-name>
<param-value>log4j2.xml</param-value>
</context-param>
keep log4j2.xml in src folder. log4j2.xml is not loaded if we keep it in classpath.

Log4j documentations:
interval -> (integer) How often a rollover should occur based on the most
specific time unit in the date pattern. For example, with a date
pattern with hours as the most specific item and and increment of 4
rollovers would occur every 4 hours. The default value is 1.
You should change the filename pattern if you would like to create it every hour.

As Abid mentioned, interval value is interpreted in context of pattern that is specified as part of filePattern. It starts with lowest denomination. For example,if pattern contains S, frequency will be in millisecond. It supports the date pattern as described in detail as part of SimpleDateFormat java doc http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html

You do have a non-empty log file (otherwise there is nothing to roll over)?
Note that even though the name is "TimeBased..." It will not actually roll over at the specified time, but at the first log event that arrives after the time threshold has been exceeded. Can you try with a small test program that logs something after 61 minutes or so and see if the problem still occurs?
If it doesn't roll over with the above test program, you may have found a bug. In that case please raise it on the log4j issue tracker. (Be sure to attach the test program the team can use to reproduce the issue).

Everyday day Rolling
<RollingFile name="RollingFile" fileName="logs/app.log"
filePattern="logs/app.%d{yyyy-MM-dd}.log" ...>
...
<TimeBasedTriggeringPolicy interval="1" modulate="true" />
Everyday Hour Rolling
<RollingFile name="RollingFile" fileName="logs/app.log"
filePattern="logs/app.%d{yyyy-MM-dd-HH}.log" ...>
...
<TimeBasedTriggeringPolicy interval="1" modulate="true" />
Everyday 5 day Rolling
<RollingFile name="RollingFile" fileName="logs/app.log"
filePattern="logs/app.%d{yyyy-MM-dd}.log" ...>
...
<TimeBasedTriggeringPolicy interval="5" modulate="true" />
Everyday 5 hours Rolling
<RollingFile name="RollingFile" fileName="logs/app.log"
filePattern="logs/app.%d{yyyy-MM-dd-HH}.log" ...>
...
<TimeBasedTriggeringPolicy interval="5" modulate="true" />
Every Month Rolling
<RollingFile name="RollingFile" fileName="logs/app.log"
filePattern="logs/app.%d{yyyy-MM}.log" ...>
...
<TimeBasedTriggeringPolicy interval="1" modulate="true" />
Hope these cases will helps very well in understanding how filePattern and interval are related.

The time interval interpretation depends on file pattern you are using. The following configuration rolls file every second for me.
<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
<Appenders>
<Console name="A" target="SYSTEM_OUT">
<PatternLayout pattern="%d [%t] %-5p {%F:%L} %x - %m%n" />
<ThresholdFilter level="INFO" onMatch="ACCEPT" onMismatch="DENY"/>
</Console>
<RollingFile name="R"
fileName="/home/xxx/yyy/myapp.log" filePattern="/home/xxx/yyy/myapp-%d{yyyy-MM-dd-HH-mm-ss}-%i.log">
<PatternLayout pattern="%d [%t] %-5p {%F:%L} %x - %m%n" />
<Policies>
<TimeBasedTriggeringPolicy interval="1" />
</Policies>
</RollingFile>
</Appenders>
<Loggers>
<Root level="INFO">
<AppenderRef ref="A" />
<AppenderRef ref="R" />
</Root>
</Loggers>
</Configuration>

According to your TimeBasedTriggeringPolicy configuration, logger will only populate the logs every day not every hour.
AFAIK,You can achieve the functionality by changing the filePattern from HH(Hours) to dd(Days).
I have modified your config.xml. Try This
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="warn" name="MyApp" packages="">
<Appenders>
<RollingFile name="RollingFile" fileName="logs/app.log" filePattern="logs/$${date:yyyy-MM}/app-%d{yyyy-MM-dd}-%i.log.gz">
<PatternLayout>
<Pattern>%d %p %c{1.} [%t] %m%n</Pattern>
</PatternLayout>
<Policies>
**
<TimeBasedTriggeringPolicy interval="1" modulate="true" />
**
<SizeBasedTriggeringPolicy size="250 MB" />
</Policies>
</RollingFile>
</Appenders>
<Loggers>
<Root level="error">
<AppenderRef ref="RollingFile" />
</Root>
</Loggers>
</Configuration>
For more details check this
Hope this will workout for you too.

Issue with logging exceptions

After porting big project to log4j2, i noticed that logging of exceptions doesn't work. Such code
logger.error("Error occurred", e);
doesn't log exception call stack. The log for the above line contains only:
21/07/2013 15:51:34 ERROR [MyTask-1] [MyManager] Error occurred
Please help to configure the logger.
Updated:
My log4j2.xml generally looks like this (i removed rest of the appenders and loggers):
<?xml version="1.0" encoding="UTF-8"?>
<configuration name="server" monitorInterval="30">
<appenders>
<!-- ################# All Appender ############################### -->
<RollingFile name="AllAppender" fileName="${sys:workspace}/logs/all.log" filePattern="${sys:workspace}/archive/logs/all_%d{yyyy-MM-dd_HH}.log">
<PatternLayout>
<pattern>%d{dd/MM/yyyy HH:mm:ss} %-5p [%t] [%c{1}] %m%n</pattern>
</PatternLayout>
<Policies>
<OnStartupTriggeringPolicy />
<TimeBasedTriggeringPolicy interval="1" modulate="true"/>
<SizeBasedTriggeringPolicy size="10 MB"/>
</Policies>
<DefaultRolloverStrategy max="50"/>
</RollingFile>
</appenders>
<loggers>
<!-- #################################################################################################### -->
<!-- ################################### Loggers definitions ############################################ -->
<!-- #################################################################################################### -->
<logger name="com" level="debug">
<appender-ref ref="AllAppender" />
</logger>
<root level="debug">
<appender-ref ref="AllAppender"/>
</root>
</loggers>
By the way, monitorInterval doesn't work for me. I have to restart tomcat in order to update logger configuration.

What version of log4j2 are you using? I remember this being an issue in older betas but it was fixed around beta5 or so... If you are using a recent beta, could you file a bug report?
As a workaround you can replace %m%n at the end of your pattern with %m%ex%n.