JoaoJandre opened a new pull request, #7131:
URL: https://github.com/apache/cloudstack/pull/7131

   ### Description
   
   This PR normalizes ACS's loggers and upgrades log4j 1.2 to log4j 2.19. Back 
in 2015, PR #714 tried to normalize the loggers but, because that normalization 
caused some issues with the VMware module, it ended up being reverted. This PR 
intends to follow that PR's footsteps and normalize all of the loggers in ACS. 
The objective of reducing unnecessary logger declarations, and reduce the area 
of impact to upgrade ACS's logger framework from log4j 1.2 to log4 2.19. 
   
   The log4j upgrade was done similarly to the proposed here 
https://github.com/apache/cloudstack/pull/2992#issuecomment-439132311, and is 
more detailed ahead.
   
   The logger normalization includes:
   - Classes that could have their loggers inherited from their ancestors had 
their own loggers deleted;
   - Most loggers didn't have to be static, thus most of them were normalized 
so that they wouldn't be;
   - loggers are protected now;
   - Static logger's names are now 'LOGGER';
   - Non-static logger's names are now 'logger';
   - New class DbUpgradeAbstractImpl created so that all Upgraders extend it 
and inherit its logger;
   - The following classes now have loggers (so that all their children can 
inherit their loggers):
   `BaseElement`, `PipelineImpl`, `AbstractRect`, `AbstractSmartLifeCycle`, 
`ManagedContextRunnable`, `Command`, `RuleApplier`, `VmWork`, 
`ModelObjectBase`, `SnapshotStrategyBase`, `VifDriver`.
   
   To normalize all the loggers in ACS, the following steps were performed:
   
   1. The DbUpgradeAbstractImpl class was created;
   2. This script https://pastebin.pl/view/6ff71b26 was used to make all the 
Upgraders extend the DbUpgradeAbstractImpl class (I manually had to correct 
some of them afterward);
   3. I ran this script https://pastebin.pl/view/89931790 for all ACS java 
classes; the, I checked if classes can inherit the logger from their ancestor*; 
if they can, then remove their current logger instantiation. If they cannot 
then leave the instantiation, but make it non-static. And in some cases, rename 
the logger references to `logger`;
   4. I tried to build ACS many times and manually fixed the errors, most of 
them were because some loggers did indeed have to be static.
   
   *The ancestor list I created came from a previous iteration of this process, 
where I tried to simply remove logger instantiation from any class that 
extended any other class, the list was created while manually fixing the errors.
   
   For the log4j upgrade, the following steps were performed:
   
   1. The relevant pom.xml files were updated;
   2. This script https://pastebin.pl/view/0b6b77f9 was used to update all the 
logger imports;
   3. I tried to build ACS many times and manually fixed the errors.
   
   About the log4j upgrade:
   
   - The DOMConfigurator does not exist in log4j2, its functionality was moved 
to the Configurator class;
   - Both NDC and MDC were merged into the ThreadContext class;
   
   Disclaimers:   
   - The new log4j2 configuration file format is not backwards compatible with 
the old one, users must update their configuration files to match with the new 
format. I used the official apache documentation to upgrade the default 
configurations, available 
[here](https://logging.apache.org/log4j/2.x/manual/migration.html#Log4j2ConfigurationFormat).
   
   - If you call EncryptorCLI manually, you must also pass the log4j2 jar path 
(which should be in the same directory as cloud-utils).
   
   The are still some points to address/discuss in order to make this PR ready:
   
   - ~~Refactor the following classes so that they can be used in 
log4j2:`SnmpTrapAppender`, `AlertsSyslogAppender`, `TestAppender`, 
`SnmpEnhancedPatternLayout`~~;
   - ~~Convert CglibThrowableRenderer functionality to log4j2;~~
   - The log4j 1.2 dependency could not be completely removed because juniper 
contrail has log4j as a dependency.
   - ~~Test logging for management, agent, usage, SSVMs and CPVMs~~
   
   ### Types of changes
   
   - [ ] Breaking change (fix or feature that would cause existing 
functionality to change)
   - [ ] New feature (non-breaking change which adds functionality)
   - [ ] Bug fix (non-breaking change which fixes an issue)
   - [X] Enhancement (improves an existing feature and functionality)
   - [X] Cleanup (Code refactoring and cleanup, that may add test cases)
   
   ### Feature/Enhancement Scale or Bug Severity
   
   #### Feature/Enhancement Scale
   
   - [X] Major
   - [ ] Minor
   
   #### Bug Severity
   
   - [ ] BLOCKER
   - [ ] Critical
   - [ ] Major
   - [ ] Minor
   - [ ] Trivial
   
   
   ### Screenshots (if appropriate):
   
   
   ### How Has This Been Tested?
   I tested if both the console and the file appenders were logging correctly 
in the management server, agents, and system VMs. 


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