loopback-connector-grpc

The gRPC connector enables LoopBack applications to interact with gRPC services.

Installation

In your application root directory, enter:
``
$ npm install loopback-connector-grpc --save
`

This will install the module from npm and add it as a dependency to the application's package.json file.

Configuration

To interact with a gRPC API, configure a data source backed by the gRPC connector:

With code:

`javascript
var ds = loopback.createDataSource('grpc', {
connector: 'loopback-connector-grpc',
spec: 'note.proto',
});
`

With JSON in datasources.json (for example, with basic authentication):

`
"gRPCDataSource": {
"name": "gRPCDataSource",
"connector": "grpc",
"spec": "note.proto",
"security": {
"type" : "basic",
"username": "the user name",
"password": "thepassword"
}
`

Data source properties

Specify the options for the data source with the following properties.

| Property | Description | Default |
|----------|-------------|-----------|
| connector | Must be 'loopback-connector-grpc' to specify gRPC connector| None |
|spec | HTTP URL or path to the gRPC specification file (with file name extension .yaml/.yml or .json). File path must be relative to current working directory (process.cwd()).| None |
|validate | When true, validates provided spec against gRPC specification 2.0 before initializing a data source. | false|
| security | Security configuration for making authenticated requests to the API. | None |

$3

Basic authentication:

`javascript
security: {
rootCerts: 'rootCerts.crt', // Path to root certs
key: 'gprc.key', // Path to client SSL private key
cert: 'grpc.crt' // Path to client SSL certificate
}
`

$3

The gRPC connector loads the API specification document asynchronously. As a result, the data source won't be ready to create models until it is connected. For best results, use an event handler for the connected event of data source:

`javascript
ds.once('connected', function(){
var PetService = ds.createModel('PetService', {});
...
});
`
Once the model is created, all available gRPC API operations can be accessed as model methods, for example:

`javascript
...
PetService.getPetById({petId: 1}, function (err, res){
...
});
`

The model methods can also be called as promises:

`javascript
PetService.getPetById({petId: 1}).then(function(res) {
...
}, function(err) {
...
});
// in async/await flavor
const res = await PetService.getPetById({petId: 1});
`

$3


Once you define the model, you can wrap or mediate it to define new methods. The following example simplifies the getPetById operation to a method that takes petID and returns a Pet instance.

`javascript
PetService.searchPet = function(petID, cb){
PetService.getPetById({petId: petID}, function(err, res){
if(err) cb(err, null);
var result = res.data;
cb(null, result);
});
};
`

This custom method on the PetService model can be exposed as REST API end-point. It uses loopback.remoteMethod to define the mappings:

`javascript
PetService.remoteMethod(
'searchPet', {
accepts: [
{ arg: 'petID', type: 'string', required: true,
http: { source: 'query' }
}
],
returns: {arg: 'result', type: 'object', root: true },
http: {verb: 'get', path: '/searchPet'}
}
);
``

$3

Coming soon...