Using gRPC for (local) inter-process communication (2021)

There's a mountain of grpc-centric python code at $dayjob and it's been miserable to live with. Maybe it's less awful in c/c++, or at least confers some decent performance there. In python it's hot garbage.

Strongly agree, it’s has loads of problems, my least favourite being the schema is not checked in the way you might think, there’s not even a checksum to say this message and this version of the schema match. So when there’s old services/clients around and people haven’t versioned their schema’s safely (there was no mechanism for this apart from manually checking in PRs) you can get gibberish back for fields that should contain data. It’s basically just a binary blob with whatever schema the client has overlaid so debugging is an absolute pain. Unless you are Google scale use a text based format like JSON and save yourself a lot of hassle.

There is an art to having forwards and backwards compatible RPC schemas. It is easy, but it is surprisingly difficult to get people to follow easy rules. The rules are as follows:

  1) Never change the type of a field
  2) Never change the semantic meaning of a field
  3) If you need a different type or semantics, add a new field

Pretty simple if you ask me.

If I got to choose my colleagues this would be fine, unfortunately I had people who couldn’t understand eventual consistency. One of the guys writing Go admitted he didn’t understand what a pointer was etc. etc.