[MCHECKSTYLE-440] how to reuse the checkstyle cache from a new environment

• Type: Task
• Status: Closed
• Priority: Major
• Resolution: Information Provided
• Affects Version/s: 3.3.0
• Component/s: checkstyle:check
• Assignee: Unassigned
• Reporter: Nianjun Sun
• Created: 08/Aug/23 11:31
• Updated: 09/Aug/23 08:23
• Resolved: 09/Aug/23 08:23

Description

Hi, dear Checkstyle plugin team,
  
This is Nianjun from the Apache/ShardingSphere team. Recently, we added the checkstyle:check as required check in our GitHub action. This action is triggered by every single pull request and checks the Java code style for all modules.
  
I noticed that running checkstyle:check takes almost 1 minute to check nearly 300 modules.this takes too much time for the reviewer to merge the code. I know that Checkstyle generates a cache file called 'checkstyle-cachefile' in the target folder. So, I tried caching all 'checkstyle-cachefile' files in the target folder by 
actions/cache@v3 for the next GitHub action run.  
However, this approach didn't work and I'm not sure how the Checkstyle cache works...
  
Interestingly, when I execute the command `mvn checkstyle:check -Dcheckstyle.skip=false -T1C` twice in our GitHub action, it only takes 15 seconds on the second run. This makes me think that the cache file is working.
  
I also tried downloading these 'checkstyle-cachefile' files from GitHub's cache and putting them in each module's target folder, but it still takes 1 minute to complete.
  
I'm not sure if 'checkstyle-cachefile' has an expiration period or if it depends on some environment information or something else entirely. Could you please provide some tips or give me a brief description of how 'checkstyle-cachefile' works?
  
Thank you!