Add a Connection Broker for GRPC plugins #52
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@mitchellh The In that file is the implementation of the GRPCBroker as well as the server/client used for the gRPC stream. |
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Whew, took a bit to work through this but this looks good.
It'd be great to see docs on how this works put into the docs/ folder. That is a recent addition (with initial grpc) so its less in depth but I'd like to start making sure we update that so that the whole system is easier to understand going forward.
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| // This is the implementation of plugin.Plugin so we can serve/consume this. |
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Should be plugin.GRPCPlugin instead of plugin.Plugin.
Nevermind, this embeds plugin.NetRPCUnsupportedPlugin which is the plugin.Plugin implementation.
grpc_broker.go
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| case s := <-s.send: |
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Minor nit, but perhaps rename s into something else, since s initially refers to *gRPCBrokerServer, but after the assignment it's a *sendErr. Even though there's not conflict in overriding s in this case, it makes it somewhat harder to read. Same for StartStream on the client side.
This adds a broker object that can serve and dial connections via connection ids. It uses a streaming gRPC service to communicate the connection details between a client and a plugin. Each
AcceptAndServecall opens a new listener socket and sends the connection info down the stream to the dialer. Since a new connection is opened every call, these calls should be used sparingly. Multiple gRPC server implementations can be registered to a singleAcceptAndServecall.Plugins written in another language will, optionally, have to implement the gRPC server/client for the broker, but we provide the proto file for this definition.
Unfortunately there is a slight API breaking change with the
GRPCPlugininterface. TheGRPCServerandGRPCClientnow accept aGRPCBrokeras the first parameter. Open to ideas on how to make this BC.