How to determine field sizes

[akutz]

#132 adds default field size limits to the spec, but I'm not sure the spec clearly identifies how to determine the size of a thing. For example, if using the gRPC wire protocol, a string takes up a byte per character. Therefore identifying the size a map<string, string> consumes in Go would entail iterating the key/value pairs, converting them to []byte slices, and the summing the lengths of those slices. Since Go string types are just arbitrary bytes, it cannot be assumed a string is always UTF-8 (string literals, however, are).

Still, that's just calculate the size of a map<string, string> in Go, not all other possible languages. I guess the question is, should field size be related to the wire protocol encoding of a field, its elements, a specific encoding, etc.?

[akutz]

cc @jdef @saad-ali @jieyu

In addition to determining field sizes, I noticed that the spec calls out string and map<string, string> types, but omits the type repeated string. Is this on purpose? For example:

  // Indicate that the volume will be accessed via the filesystem API.
  message MountVolume {
    // The filesystem type. This field is OPTIONAL.
    // An empty string is equal to an unspecified field value.
    string fs_type = 1;

    // The mount options that can be used for the volume. This field is
    // OPTIONAL. `mount_flags` MAY contain sensitive information.
    // Therefore, the CO and the Plugin MUST NOT leak this information
    // to untrusted entities. The total size of this repeated field
    // SHALL NOT exceed 4 KiB.
    repeated string mount_flags = 2;    
  }

Should the field mount_flags be limited to the same 4KiB size limit that applies to map data?

[saad-ali]

Still, that's just calculate the size of a map<string, string> in Go, not all other possible languages. I guess the question is, should field size be related to the wire protocol encoding of a field, its elements, a specific encoding, etc.?

Yes we should clarify the how size is calculated.

Should the field mount_flags be limited to the same 4KiB size limit that applies to map data?

Yes, that would be good to do.

[saad-ali]

Not a blocker for 1.0.rc