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9. Considering the HA, traffic controller should instantiate at least 2 of those plugins, and should be
    able to monitor the health of those instances of plugins. when any of instances is down, traffic controller
    can restart/recreate one for it again.

LoadBalancer (aka LB controller?)

LBer(controller) is used to balance incoming load across multiple istio-ingress-gateways. It shall be able to be aware
of the run-time load of various working uService instances which are distributed on different edge clouds or the general
load level of each kind of uService in each edge cloud by interacting with actual LB(e.g. metallb, or other module except metallb)
running on one edge cloud. Metallb is responsible for the load balance jobs between instances of uService within an edge cloud,
while LBer(controller) shall be in charge of guiding the traffic load to multiple edge clouds. LBer(controller) should be aware of
the public IPs (achieved by using metallb? or SDWAN?) of all edge clouds. 

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Sequence flows

Test cases

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