Adds automation for generating the map of `gRPC Method Name → Rate Limit Type`
used by the middleware introduced in #15550, and will ensure we don't forget
to add new endpoints.
Engineers must annotate their RPCs in the proto file like so:
```
rpc Foo(FooRequest) returns (FooResponse) {
option (consul.internal.ratelimit.spec) = {
operation_type: READ,
};
}
```
When they run `make proto` a protoc plugin `protoc-gen-consul-rate-limit` will
be installed that writes rate-limit specs as a JSON array to a file called
`.ratelimit.tmp` (one per protobuf package/directory).
After running Buf, `make proto` will execute a post-process script that will
ingest all of the `.ratelimit.tmp` files and generate a Go file containing the
mappings in the `agent/grpc-middleware` package. In the enterprise repository,
it will write an additional file with the enterprise-only endpoints.
If an engineer forgets to add the annotation to a new RPC, the plugin will
return an error like so:
```
RPC Foo is missing rate-limit specification, fix it with:
import "proto-public/annotations/ratelimit/ratelimit.proto";
service Bar {
rpc Foo(...) returns (...) {
option (hashicorp.consul.internal.ratelimit.spec) = {
operation_type: OPERATION_READ | OPERATION_WRITE | OPERATION_EXEMPT,
};
}
}
```
In the future, this annotation can be extended to support rate-limit
category (e.g. KV vs Catalog) and to determine the retry policy.
Previously, public referred to gRPC services that are both exposed on
the dedicated gRPC port and have their definitions in the proto-public
directory (so were considered usable by 3rd parties). Whereas private
referred to services on the multiplexed server port that are only usable
by agents and other servers.
Now, we're splitting these definitions, such that external/internal
refers to the port and public/private refers to whether they can be used
by 3rd parties.
This is necessary because the peering replication API needs to be
exposed on the dedicated port, but is not (yet) suitable for use by 3rd
parties.
Ronald