Expose response status and metadata

[bojand]

Currently for unary and request stream calls there is no easy way to get metadata and status if we want those

Server:

function sayHello(call, callback) {
  const md = new grpc.Metadata()
  md.set('foo', 'bar')
  call.sendMetadata(md)

  const smd = new grpc.Metadata()
  smd.set('biz', 'baz')
  callback(null, { message: 'Hello ' + call.request.name }, smd);
}

With the core client:

const call = client.sayHello({ name: user }, function (err, response) {
  console.log('response')
  console.log(response)
});

call.on('metadata', m => {
  console.log('metadata')
  console.dir(m, {depth: 4, colors: true})
})

call.on('status', m => {
  console.log('status')
  console.dir(m, {depth: 4, colors: true})
})

metadata
Metadata { _internal_repr: { foo: [ 'bar' ] } }
response
{ message: 'Hello world' }
status
{ code: 0,
  details: 'OK',
  metadata: Metadata { _internal_repr: { biz: [ 'baz' ] } } }

[bojand]

A proposal:

From an api perspective... we could keep the present api for easy of use, simplicity, and compatibility. In addition we could introduce a new "lower-level" Request and Response API, something similar to:

Fluent Request API:

const caller = require('grpc-caller')
const PROTO_PATH = path.resolve(__dirname, './protos/helloworld.proto')
const client = caller('0.0.0.0:50051', PROTO_PATH, 'Greeter')

const req = new client.Request('sayHello', { name: 'Bob'}) // the method we wish to invoke with the params
  .setOptions({}) // any normal "call" options
  .setMetadata({'request-id': '1234'}) // request call metadata
  .responseMetadata(true) // we care about getting the response metadata, if false we won't wait for and catch the 'metadata' event
  .responseStatus(true) // we care about getting the response status, if false we won't wait for and catch the 'status' event

const res = await req.exec() // promise based, optionally take callback for callback-based API

console.log(res.response) 
// the response payload / "body"
// { message: 'Hello Bob!' }

console.log(res.metadata) 
// the response "header" metadata converted into a map for us
// { foo: 'bar' }

console.log(res.status) 
/*
the response status / trailer metadata: 
{ code: 0,
  details: 'OK',
  metadata: { biz: 'baz' } }
*/

console.log(res.call) // just the call instance itself

We could wrap the above in an simpler functional API:

const res = await client.request('sayHello', { name: 'Bob'}) 
  .setOptions({})
  .setMetadata({'request-id': '1234'})
  .responseMetadata(true)
  .responseStatus(true)
  .exec()

or callback based:

client.request('sayHello', { name: 'Bob'}) 
  .setOptions({})
  .setMetadata({'request-id': '1234'})
  .responseMetadata(true)
  .responseStatus(true)
  .exec((err, res) => {
    console.log(res.response)
})

Underneath the present "simple" API would be implemented using the more verbose API.

[yoitsro]

Hey @bojand. First, thanks for all your gRPC work with Node. I appreciate it massively!

Second, how's progress coming along with this? I've seen you've got your req_res branch in progress and it's looking good so far!

I need access to the response metadata, hence why I'm here :)

[bojand]

Hello, Yea I think I got it mostly working but wasn't really happy with the resulting API or something for some reason and I think I kind of abandoned it... Don't remember now heh. I'll have to return to this soon and review it with a clearer mind now and see what's up.

[bojand]

@yoitsro I believe #11 adds the functionality. Please provide feedback on the new API. Note that now you have to explicitly add grpc dependency in your package.json. Thanks!

[yoitsro]

@bojand Thank you so much for this! I've not had chance to check it out yet, but will do in a few days time. And yeah, it makes sense having grpc required separately. It's similar to what I do with https://github.com/yoitsro/joigoose and mongoose :)

[bojand]

#11 is merged and published as 0.5.0.