Creating daily logs with Log4j?

Question

What configuration values are needed to setup Log4j to use the following pattern?
MyApp-Mon.log
MyApp-Tue.log
MyApp-Wed.log
Etc

With each file containing the days log.

This sounds easy enough to do with Log4j's DailyRollingFileAppender but I am having trouble.
Here is my current config;

<appender name="daily-file" class="org.apache.log4j.DailyRollingFileAppender">
    <param name="Threshold" value="info"/>
    <param name="DatePattern" value="'-'EE'.log'"/>
    <param name="file" value="MyApp"/>
    <param name="Append" value="true" />
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{EEE MMM dd hh:mm:ss zzz yyyy} %-5p %l - %m%n"/>
    </layout>
</appender>

I based this config on this blog post, but it is not behaving in the way he describes. The log is being created as MyApp with no extension.

Can anyone help me out here?

Answer 1

the current logfile is named MyApp, then tomorrow it will be renamed by Myapp-yesterday and so on

but the current log has always the default name.

Answer 2

Looking at the JavaDocs for the DailyRollingFileAppender, all the examples they set out have specific, numeric date patterns, not day-name patterns. Have you tried to see if using one of their examples works? If so, and yours doesn't, then I'd assume that the DailyRollingFileAppender doesn't support the use of a date pattern containing 'E' (the day of the week).

Answer 3

I based this config on this blog post, but it is not behaving in the way he describes. The log is being created as MyApp with no extension.

This is what you told Log4J to do with this line:

<param name="file" value="MyApp"/>

Log4J uses the value of this option as log file name and the pattern is only applied when the roll over occurs, as documented:

For example, if the File option is set to /foo/bar.log and the DatePattern set to '.'yyyy-MM-dd, on 2001-02-16 at midnight, the logging file /foo/bar.log will be copied to /foo/bar.log.2001-02-16 and logging for 2001-02-17 will continue in /foo/bar.log until it rolls over the next day.

So everything looks normal to me.

To obtain the desired behavior, you could write your own Appender. It looks like James Stauffer did something very similar (see this answer) but he extends FileAppender. It should be easy to adapt his work for a DailyRollingFileAppender subclass though.

Answer 4

In response to your comment to Pascal's answer:

Would a ln -s MyApp.log MyApp-NOW.log work? Your legacy log viewer would show MyApp-NOW.log via the symbolic link and log4j can roll-over MyApp.log to MyApp-TUE.log at midnight.