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P5: Require a gRFC for large scale changes to gRPC core #233
P5: Require a gRFC for large scale changes to gRPC core #233
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I think this bullet in particular needs to be more nuanced. I do absolutely agree that a gRFC is appropriate for large structural changes to these kinds of APIs, but I think we also have a lot of changes to these APIs that are smaller in scope, where requiring a gRFC doesn't seem like a positive cost/benefit trade-off.
In particular, the resolver and LB policy APIs have been seeing a fair amount of small changes over time, some as part of the xDS work and others just as we evolve the client channel architecture, which we've currently been free to do since they are not yet public APIs. It's been very convenient to make these kinds of changes happen slowly over time, and I think that would be a much heavier-weight approach if every small change required a gRFC.
To make this more concerete, here are some examples of actual changes we've made to these APIs over the years, grouped based on whether or not I think the change should require a gRFC moving forward:
First, the changes that I think should require a gRFC:
ResultHandler
interface) and Restructure how addresses and service config are passed from resolver to LB policy grpc#18357 (restructure how addresses flow from resolver to LB policy)Here are a few that I think are borderline; the scope or impact of the changes probably justifies a gRFC, but the fact that there don't happen to be any external LB policy implementations today mean that the changes didn't affect anyone:
CreateSubchannel()
separately instead of encoding in channel args)ConnectedSubchannel
from LB policy API)And here are the ones that I think are small enough that they should not require a gRFC:
WorkSerializer
orResultHandler
)std::function<>
for LB policy callback to intercept trailing metadata)CreateChannel()
from LB policy helper API)absl::Status
)RequestReresolutionLocked()
must immediately return a new result)NextLocked()
semantics to differentiate between fatal and transient failures)(I think there are more in that last category, but I didn't take the time to go back further into the history.)
Given the above, I propose something like the following for these extension points:
WDYT?
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Not opposed, but wanted to throw out an alternative:
This gRFC includes a light-weight update procedure for prior gRFC's that fall into it's domain.
Suppose we retroactively document the interfaces we're worried about here and publish them as gRFC's and then going forward we use the update process (and tune the timing to something that makes sense).
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Isn't this one already covered by P3? If not, can you give an example of what would be included in this?
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I think I was thinking about internal extensibility... I'll clean this one up.
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Can you give an example of this?
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One that's happened before: L6 introduced the restriction that a C++11 compiler was required to compile Core, L59 required a standard library be dynamically linkable. Neither formally required a gRFC (no API changes), but we did so anyway because it felt right - this tries to formalize that.
New changes that might fall into that: taking a large dependency, refactoring in a way that prevents a known use case... things that would require a large scale change to undo.
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Changed text.
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Same question here, an example would help.
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Added some text.