The patch proposes adding a new binding_index to the
RouterL3AgentBinding table, with an additional Unique Constraint that
enforces a single <router_id, binding_id> per router. This goes a long
way into fixing 2 issues:
1. When scheduling a non-HA router, we only use binding_index=1. This
means that only a single row containing that router_id can be
committed into the database. This in fact prevents over-scheduling of
non-HA routers. Note that for the HA router case, the binding_index
is simply copied from the L3HARouterAgentPortBinding (since they are
always created together they should always match).
2. This sets the ground-work for a refactor of the l3 scheduler - by
using this binding and db-based limitation, we can schedule a router
to agents using the RouterL3AgentBinding, while postponing the
creation of L3HARouterAgentPortBinding objects for the agents until
they ask for it (using sync_routers). This will be a major
improvement over todays "everything can create
L3HARouterAgentPortBinding" way of things).
Closes-Bug: #1535557
Change-Id: I3447ea5bcb7c57365c6f50efe12a1671e86588b3
b1ec8d523d