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Support Article

Logging behaviour is different between prlogging and prlog4j

SA-64217

Summary



Post upgrade to Pega 7.3.1, the new prlog4j2.xml prevents the creation of the current log file with the current date.

In Pega 7.1.8, log file can be defined with the date and saved. When the system is rolled over, a new file is created with the current date and it can be the current log file.

When creating the log filename without a date, the rollover for filename occurs correctly. However, the log management using Splunk does not work.



Error Messages



Not Applicable


Steps to Reproduce

  1. Update from Pega 7.1.8 to Pega 7.3.1.
  2. Add a filename in the appender, such as fileName="${sys:pega.logdir}/PegaRULES-${date:MM-dd-yyyy}.log".

This creates the log file during the initial start up. However, after rollover, two files are named as: 

  • PegaRULES-08-15-2018.log
  • PegaRULES-08-15-2018-1.log

The actual date is retained and 1 is added at the end.


Root Cause



Log4j2 does prevents the addition of a date to the filename for RollingRandomAccessFile appender. Adding a date, causes the rolling behavior to not use the date.


Resolution



Here's the explanation for the reported behavior:

In the earlier log4j implementation, used in the earlier Pega applications, appenders are declared as below:

    <appender name="PEGA" class="com.pega.pegarules.priv.util.DailySizeRollingFileAppenderPega">
      <param name="FileNamePattern" value="'C:/PRPC/PRPCLogs/719/PegaRULES-'yyyy-MMM-dd'.log'"/>
      <param name="MaxFileSize" value="50MB" />
      <layout class="com.pega.apache.log4j.PatternLayout">
       <param name="ConversionPattern" value="%d [%20.20t] [%10.10X{pegathread}] [%20.20X{tenantid}] [%20.20X{app}] (%30.30c{3}) %-5p %X{stack} %X{userid} - %m%n"/>
      </layout>
     </appender>

Only a FileNamePattern parameter is used to accept a filename and specify a date as above.
As a result, when the server is started, a log file is created using the above example with the "PegaRULES-2018-Aug-20.log" current date.
At midnight, the system creates "PegaRULES-2018-Aug-21.log" which is a new log file. All the current log items enter this new file.

In log4j2, this works differently. The file appender and has two parameters (fileName and filePattern) instead of one as in the older version.

For example,

        <RollingRandomAccessFile  name="PEGA" fileName="${sys:pega.logdir}/PegaRULES.log" filePattern="${sys:pega.logdir}/PegaRULES-%d{MM-dd-yyyy}-%i.log.gz">
            <PatternLayout>
                <Pattern>%d [%20.20t] [%10.10X{pegathread}] [%20.20X{tenantid}] [%20.20X{app}] (%30.30c{3}) %-5p %X{stack} %X{userid} - %m%n</Pattern>
            </PatternLayout>
            <Filters>
                <!--Deny message logged under ALERT log level-->
                <ThresholdFilter level="ALERT" onMatch="DENY" onMismatch="NEUTRAL"/>
            </Filters>        
            <Policies>
                <TimeBasedTriggeringPolicy />
                <SizeBasedTriggeringPolicy size="250 MB"/>
            </Policies>
            <DefaultRolloverStrategy max="20"/>
        </RollingRandomAccessFile>   

This logs to one file with a static file name. For example, PegaRULES.log.

The content is moved to another file, for example, PegaRULES-08-20-2018.log.

However, the system continues to log to PegaRULES.log.

According to the Apache website, the RollingFileAppender works in Log4j2 2.8. However, the RollingRandomAccessFile does not work according to the JIRA item.

Published October 28, 2018 - Updated October 8, 2020

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