Help me to understand what sort of communicaiton /information will transform from ICINGA Web to POSTGRES DB and vice versa ?
Advantage of using Two Masters? if we decide to not to use HA?
Hello there!
Could you maybe specify your questions a little more? They are a little too broad for me to answer properly, and I think you would also get better answers if you opened separate topics for each question, going in a bit more detail about the background of your questions.
I will just link you some documentation here, so you can do your research a little easier, hope that helps 
About the database there are these resources to read up on: Ressources Database and if you’re feeling like a deep dive: Icinga 1 docs about the DB model.
You can read up on distributed monitoring here.
Have a nice week!
Feu