FQDNS - Module

[ESiebigteroth]

Description:
With the current implementation (in salt core grains), when there is a DNS misconfiguration, salt would get stuck/crash in unpredictable ways.
Moving the fqdns computation to a salt module would keep salt core grains fast and reliable.

Impact:

This change would impact SUSE Manager, so adaptations are required.
This can also impact a customer that is currently using the fqdns grains from Salt (if any). They would still have access to the information but they would have to call the salt module to retrieve it (available on demand not by default). Because of this, we have to document it in the release notes.

Pros:

Make salt more reliable by keeping the core grains fast and reliable
Prevent L3s from customers with misconfigured DNS (hard to see it is a DNS problem, they could see that salt-minion is taking a long time to start and would thing it's a performance problem in Salt)

Todo:

• check saltstack/salt documentation for grains

• check saltstack/salt writing a custom module

• create your custom module

• check code for current implementation

• update your custom module with the above implementation

• check salt modules reference list for a better home for your module

• refactor (DRY)

• make sure the core grains are still working after refactoring

• add configuration parameter to disable fqdns grains (true by default)

• write tests for the module and for grains (if don't exist) and for the parameter

• write some documentation:

  • Try to find where the source for this pages is:
    • https://docs.saltstack.com/en/latest/ref/grains/all/salt.grains.core.html
    • https://docs.saltstack.com/en/latest/ref/modules/all/salt.modules.network.html
  • Add section for the parameter to disable core.fqdns grains
  • Add link to documentation for network.fqdns module (new home)
  • Add documentation for network.fqdns in the salt.modules.network doc page

• Take a look at the release process for the package https://github.com/openSUSE/salt/wiki/Workflow (it will be useful once your PR will be accepted)