[GitHub] [arrow] zeroshade commented on a change in pull request #10297: ARROW-12746: [Go][Flight] append instead of overwriting outgoing metadata

[GitBox <gi...@apache.org>]

zeroshade commented on a change in pull request #10297:
URL: https://github.com/apache/arrow/pull/10297#discussion_r630587448



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File path: go/arrow/flight/client_auth.go
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@@ -65,7 +65,7 @@ func createClientAuthUnaryInterceptor(auth ClientAuthHandler) grpc.UnaryClientIn
 			return status.Errorf(codes.Unauthenticated, "error retrieving token: %s", err)
 		}
 
-		return invoker(metadata.NewOutgoingContext(ctx, metadata.Pairs(grpcAuthHeader, tok)), method, req, reply, cc, opts...)

Review comment:
       the `ctx` variable passed in is the "context" that was created by the caller and passed. The user could add metadata (ie: headers) to the context by calling `NewOutgoingContext`. The problem is that by calling `NewOutgoingContext` here, we're dropping any metadata they had stuck in the context and replacing it with the auth metadata. So they're gonna lose any extra headers/metadata a caller intended on passing with the request.
   
   By calling `AppendToOutgoingContext` if there is no metadata it'll create some, but if there already is metadata in the context that was placed there by the caller, we're just gonna add the authentication header to the metadata, preserving the caller's metadata instead of dropping it completely.




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