To ease the transition for users, the original gRPC
port can still operate in a deprecated mode as either
plain-text or TLS mode. This behavior should be removed
in a future release whenever we no longer support this.
The resulting behavior from this commit is:
`ports.grpc > 0 && ports.grpc_tls > 0` spawns both plain-text and tls ports.
`ports.grpc > 0 && grpc.tls == undefined` spawns a single plain-text port.
`ports.grpc > 0 && grpc.tls != undefined` spawns a single tls port (backwards compat mode).
The client is set to send keepalive pings every 30s. The server
keepalive enforcement must be set to a number less than that,
otherwise it will disconnect clients for sending pings too often.
MinTime governs the minimum amount of time between pings.
Previously, public referred to gRPC services that are both exposed on
the dedicated gRPC port and have their definitions in the proto-public
directory (so were considered usable by 3rd parties). Whereas private
referred to services on the multiplexed server port that are only usable
by agents and other servers.
Now, we're splitting these definitions, such that external/internal
refers to the port and public/private refers to whether they can be used
by 3rd parties.
This is necessary because the peering replication API needs to be
exposed on the dedicated port, but is not (yet) suitable for use by 3rd
parties.
Derek Menteer