Allow to dynamically change log filename using {dynamic name} segment

[simon04]

Description

Allow to dynamically change log filename. Say you have a task consisting of the steps foo, bar, baz, and you'd like to obtain log files foo.log, bar.log, baz.log

This PR would allow to:

Configuration.set("writer.file", "logs/{dynamic name: init}.log");
Configuration.set("writer.policies", "dynamic name");
runInit(); // logs are written to logs/init.log
DynamicNameSegment.setDynamicName("foo");
runFoo(); // logs are written to logs/foo.log
DynamicNameSegment.setDynamicName("bar");
runBar(); // logs are written to logs/bar.log
DynamicNameSegment.setDynamicName("baz");
runBaz(); // logs are written to logs/baz.log

Would you be willing to support this feature? Is this draft implementation a feasible way to accomplish the goal? Is there a more concise way?

Definition of Done

• I read contributing.md
• There are no TODOs left in the code
• Code style follows the tinylog standard
• All classes and methods have Javadoc
• Changes are covered by JUnit tests including edge cases, errors, and exception handling
• Maven build works including compiling, tests, and checks (mvn verify)
• Changes are committed by a verified email address that is assigned to the GitHub account (https://github.com/settings/emails)

Documentation

Additions or amendments for the public documentation:

• document dynamic name segment including example code from above
• document dynamic name policy

Agreements

• I agree that my changes will be published under the terms of the Apache License 2.0 (mandatory)
• I agree that my GitHub user name will be published in the release notes (optional)

[pmwmedia]

Thank you for your pull request, and yes, I'm willing o support this feature.

Improvement suggestions:

• Fix the code style
• Support an initial log name as parameter aka log file reset: my-log-file
• LogFileResetPolicy does not need to be based on DailyPolicy (if you need both, you can configure it on runtime via daily, log file reset)
• I'm not completely happy with the names LogFileResetPolicy and LogFileSegment, but I don't know a better name by now

[simon04]

• Fix the code style

Done.

• Support an initial log name as parameter aka log file reset: my-log-file

Done.

• LogFileResetPolicy does not need to be based on DailyPolicy (if you need both, you can configure it on runtime via daily, log file reset)

Very nice!

• I'm not completely happy with the names LogFileResetPolicy and LogFileSegment, but I don't know a better name by now

Me neither. I also dislike the cross dependency between the two classes. Is there a better way? Should one class implement both interfaces?

Related (and more elaborated) concepts in other logging libraries are:

• http://logback.qos.ch/manual/appenders.html#SiftingAppender
• https://logging.apache.org/log4j/2.x/manual/appenders.html#RoutingAppender

[pmwmedia]

You can fix the build by adding a bug pattern for ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD for org.tinylog.policies.LogFileResetPolicy into configuration/spotbugs-filters.xml.

[pmwmedia]

Some thoughts and suggestions:

• The actual log name could be stored in LogFileSegment instead of LogFileResetPolicy. This will make the LogFileResetPolicy a bit more complex, but allows to use the LogFileSegment without having a LogFileResetPolicy.
• Currently, my favorite naming would be DynamicNameSegment and DynamicNamePolicy. However, other ideas are welcome :)
• I have just noticed that JUnit tests for LogFileResetPolicy are missing.
• I thought about merging the segment and policy to a single class. However, I think having separate classes are better readable and maintainable.

[codecov]

Codecov Report

Merging #230 (b9893ed) into v2.5 (57a450b) will decrease coverage by 0.04%.
The diff coverage is 80.76%.

@@             Coverage Diff              @@
##               v2.5     #230      +/-   ##
============================================
- Coverage     94.59%   94.54%   -0.05%     
- Complexity     2722     2741      +19     
============================================
  Files           136      138       +2     
  Lines          5220     5246      +26     
  Branches        686      689       +3     
============================================
+ Hits           4938     4960      +22     
- Misses          154      157       +3     
- Partials        128      129       +1     

Impacted Files	Coverage Δ
...main/java/org/tinylog/path/DynamicNameSegment.java	75.00% <75.00%> (ø)
...n/java/org/tinylog/policies/DynamicNamePolicy.java	83.33% <83.33%> (ø)
...pl/src/main/java/org/tinylog/path/DynamicPath.java	95.00% <100.00%> (+0.08%)	⬆️
...in/java/org/tinylog/writers/RollingFileWriter.java	82.75% <0.00%> (+0.86%)	⬆️

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[pmwmedia]

The release build fails because Java 6 does not support java.util.Objects.equals().

[pmwmedia]

The code looks perfect! I found only a view Javadoc issues.

[pmwmedia]

Thank you for your changes. It looks perfect for me :)

[simon04]

Thank you for your patient and constructive reviews!

Sorry for a few glitches in Java 6 compatibility – I'm no longer used to write code targetting Java 6...

[github-actions]

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