RPC

INTRO

As you may know, Erlang has its own binary encoding BERT inside its virtual machine, called BEAM. For enterprise RPC usually, you use protobuf or MessagePack or Thrift or ASN.1 binary parser generators. However, as you may know Erlang is not so fast in any tasks except moving binaries between sockets. So we at Synrc usually use native Erlang BERT encoding on all clients with zero encoding/decoding on server side.

The encoders/decoders could be of two types: strict (with checking the model for particular type signature with Sums and Products) and general which encode/decode anything that can be translated into correct encoding. For example, JavaScript encode/decode generator presented in this repo is just like that (it doesn’t check types and constants, given in Erlang HRL files). However, Swift version has the ability to check encoded/decoded term to comply the Erlang Type Specification.

Samples

First, you can choose the language which is not presented in this repo and try to implement your own BERT enc/dec generator for this language using Swift (Type Spec precise) and JavaScript (open relay) generator as examples.

The aim of this contest is to create encoders/decoders for each language and make bridges to other protocol descriptive formats like Can’n’Proto or protobuf!

Erlang HRL


  -record(error, { code=[] :: [] | binary() }).


  -record(ok, { code=[] :: [] | binary() }).


  -record(io, { code=[] :: [] | #ok{} | #error{},
                data=[] :: [] | <<>> 
                  | { atom(), binary() | integer() } }).

Swift Model


  class Err {
    var code: AnyObject?
  }


  class Ok {
    var code: AnyObject?
  }


  class Io {
    var code: AnyObject?
    var data: AnyObject?
  }

Swift Spec


  Chain(types: [
     Model(value:Tuple(name: "io", body: [
          Model(value:Chain(types: [
               Model(value: Tuple(name:"ok", body: [
                    Model(value:Atom())])),
               Model(value: Tuple(name:"error", body: [
                    Model(value:Atom())]))])),
          Model(value:Tuple(name:"", body:[
               Model(value:Atom()),
               Model(value:Chain(types: [
                    Model(value:Binary()),
                    Model(value:Number())]))]))])) ])

JavaScript


  function check() {
    var res = true;
    //@TODO: MORE TEST DATA
    testData = [
        1,
        [1, 2, 3],
        "string",
        {tup: 'io', code: 'login', data: {tup: '$', 0: 'Auth', 1: 12}},
        {tup: 'io', code: 'login', data: {tup: 'Auth'}},
        {tup: 'io', code: 'login', data: {tup: '$', 0: 'doe', 1: 12}},
        {tup: 'Roster', userlist: [{tup: 'Contact'}], status: 'get'},
        {tup: 'p2p', from: 'john', to: 'doe'},
        {tup: 'Profile', accounts: [1], status: 'maxim'}
    ];
    testData.forEach(function (o) {
        var o = JSON.stringify(o);
        var d = JSON.stringify(
                decode(dec(enc(encode(o)).buffer)))
                 .replace(/\\/g, '');

        if (JSON.stringify(o) != JSON.stringify(
             decode(dec(enc(encode(o)).buffer)))) {
            console.log("Original: " + o + " #&60;=&&62; Decode: " 
                + d + " %c [Error]", "color: red");
            res = false;
        } else {
            console.log("Data: " + o + " %c [OK]", "color: green");
        }
    });

    return res;
  }

Protobuf Sample

Erlang BERT/HRL (source):


 -type authType()   :: google_api | facebook_api | mobile |
                       email | voice | resend | verify | 
                       push | logout | get | delete | clear.

 -type authStatus() :: invalid_version | mismatch_user_data |
                       number_not_allowed | session_not_found |
                       attempts_expired | invalid_sms_code |
                       invalid_jwt_code | permission_denied |
                       invalid_data.

 -record('Feature',  { id    = [] :: [] | binary(),
                       key   = [] :: [] | binary(),
                       value = [] :: [] | binary(),
                       group = [] :: [] | binary()}).

 -record('Auth',     { client_id   = [] :: [] | binary(),
                       dev_key     = [] :: [] | binary(),
                       user_id     = [] :: [] | binary(),
                       phone       = [] :: [] | binary(),
                       token       = [] :: [] | binary(),
                       type        = email :: authStatus(),
                       sms_code    = [] :: [] | binary(),
                       attempts    = [] :: [] | integer(),
                       services    = [] :: list(atom()),
                       settings    = [] :: list(#'Feature'{}),
                       push        = [] :: [] | binary(),
                       os          = [] :: [] | ios | android | web,
                       created     = [] :: [] | integer(),
                       last_online = [] :: [] | integer() }).

Proto V3 (target):


 enum osEnum {
    ios = 0;
    android = 1;
    web = 2;
 }

 enum authStatus {
    invalid_version = 0;
    mismatch_user_data = 1;
    number_not_allowed = 2;
    session_not_found = 3;
    attempts_expired = 4;
    invalid_sms_code = 5;
    invalid_jwt_code = 6;
    permission_denied = 7;
    invalid_data = 8;
 }

 message Feature {
    string id = 1;
    string key = 2;
    string value = 3;
    string group = 4;
 }

 message Auth {
    string client_id = 1;
    string dev_key = 2;
    string user_id = 3;
    string phone = 4;
    string token = 5;
    authStatus type = 6;
    string sms_code = 7;
    int64 attempts = 8;
    repeated google.protobuf.Any services = 9;
    repeated Feature settings = 10;
    string push = 11;
    osEnum os = 12;
    int64 created = 13;
    int64 last_online = 14;
 }

Run


 $ mad com
 ==> "/Users/maxim/depot/synrc/bert"
 Generated Protobuf Model: "priv/protobuf/authType.proto"
 Generated Protobuf Model: "priv/protobuf/authStatus.proto"
 Generated Protobuf Model: "priv/protobuf/Feature.proto"
 Generated Protobuf Model: "priv/protobuf/Auth.proto"
 Generated Protobuf Model: "priv/protobuf/AuthError.proto"
 Compiling /src/bert_sample.erl
 OK

Credits

Yuri Maslovsky — ERLANG
Maxim Sokhatsky — GOOGLE, JAVASCRIPT
Dmytro Boiko — ERLANG, JAVASCRIPT
Anton Makarov — SWIFT
Viacheslav Katsuba — JAVASCRIPT