I have two TomCat servers. They are redundant and of equal weight.
They talk to a DB, it is replicated across 3 nodes, A->B->C (a chain, not a tree like A->B & A->C)
The DB servers need to know who is master so that one can always be enabled as a master (ie: RO mode off.) The Tomcat servers also need to know this, but they can determine that by seeing which DB is in RW mode.
How do you determine who should be the DB master? How you determine who has failled, how do you define such a failure?
(ie: if B dies, C DOESN'T become the master because A is still fine, unless A died too. If C can't see A or B, is it master? or did it's network card fail?) |
