Update documentation to reflect protobuf limitation of 2GB

[easwars]

Based on the internal post https://yaqs.corp.google.com/eng/q/4724221033530261504#a1n3, the protobuf team is adding documentation about the 2GiB limit of protobuf message size. We should probably link to that, from our call options: MaxCallRecvMsgSize and MaxCallSendMsgSize

See internal update to the doc: https://critique.corp.google.com/cl/564773603

[dfawley]

We should probably link to that, from our call options: MaxCallRecvMsgSize and MaxCallSendMsgSize

It's fine to mention it, but of course protobuf isn't the only codec we support, so things should be written with that in mind.

[arvindbr8]

@easwars -- does that mean our default here is slightly more than supported?

grpc-go/rpc_util.go

Line 360 in fd9ef72

// `math.MaxInt32`.

MaxInt32 = 2.147483647 GB

[arvindbr8]

@easwars -- I have a feeling we might confuse users by mentioning the limit thats limited to protobuf encoding. Do you still strongly feel that we should include it?

[easwars]

I understand that users who deal with messages which are anywhere close to this size are a very very small fraction, and putting this detail in the docstring might confuse others. So, I'm ok closing this or mentioning this is one of our examples/guides dealing with encoding.

[easwars]

The size limits have made it to the official protobuf docs: https://engdoc.corp.google.com/eng/doc/devguide/proto/programming-guides/encoding.md?cl=head#size-limit