Hey @eoogbe, should this be done against api_core instead? (we're about to drop gax)

@jonparrott When you say "about to", how soon do you mean? Routing headers are pretty critical path.

@lukesneeringer and @landrito can speak to that.

@eoogbe I also thought about this a while and I can't see why we need this. Metadata can already be specified by gapic clients in the generated method.

For example, we could update this generated code:

def create_book(self, name, read=False, ...):
    request = book_pb2.Book(
        name=name,
        read=read,
    )

    return self._create_book(request, ...)

to just this:

def create_book(self, name, read=False, ...):
    request = book_pb2.Book(
        name=name,
        read=read,
    )

    metadata = [
        ('x-google-request-params',
         'name={}&book.read={}'.format(request.name, request.read)),
    ]

    return self._create_book(
        request, metadata=metadata, ...)

Therefore obviating the need for this complex "overlay" logic. Am I missing something?

@jonparrott Fair enough

Cool - glad we could figure out a simpler solution. :)