balancer: establish only one TCP connection with the same endpoint, …

[cfc4n]

[fixed] #3192

[linux-foundation-easycla]

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• ❌ CFC4N (3b5e004)

[menghanl]

It's a feature for the users to create multiple TCP connections to same endpoint, if that's what they want.
Multiple TCP connections are only created if the metadata field is set to different values.
It's user's responsibility to set metadata accordingly to control number of TCP connections.

I think the current behavior is correct, and this is the old balancer API, which is already deprecated. Please try the new balancer API (https://godoc.org/google.golang.org/grpc/balancer)