Strongloop app does not load local datasource

Question

I want to use different environment specific datasource configurations in a Strongloop app. I saw at https://docs.strongloop.com/display/public/LB/Environment-specific+configuration that the priority of configurations are:

1. Environment-specific configuration, based on the value of NODE_ENV; for example, server/config.staging.json.
2. Local configuration file; for example, server/config.local.json.
3. Default configuration file; for example, server/config.json.

I have declared three datasource conf files: datasources.json:

{}

datasources.local.json:

{
  "db": {
    "name": "db",
    "connector": "loopback-connector-mongodb",
    "host":"127.0.0.1",
    "port": "27017",
    "database": "woowDev"
  }
}

and datasources.staging.js:

module.exports = {
  db: {
    connector: 'mongodb',
    hostname: process.env.OPENSHIFT_MONGODB_DB_HOST,
    port: process.env.OPENSHIFT_MONGODB_DB_PORT,
    user: process.env.OPENSHIFT_MONGODB_DB_USERNAME,
    password: process.env.OPENSHIFT_MONGODB_DB_PASSWORD,
    database: 'woow'
  }
};

Now unless I put the configuration of datasources.local.json in datasources.json it does not work. I keep getting the error: AssertionError: User is referencing a dataSource that does not exist: "db"

I tried also to add the local conf to staging conf and defined the variable NODE_ENV, but it would not load neither datasource.staging.js. I defined the NODE_ENV by doing:

export NODE_ENV=staging

Answer 1

I used node-debug to track down the issue. And it came in this particular source strongloop file:

node_modules/loopback-boot/lib/config-loader.js

the function:

function mergeDataSourceConfig(target, config, fileName) {
  for (var ds in target) {
    var err = applyCustomConfig(target[ds], config[ds]);
    if (err) {
      throw new Error('Cannot apply ' + fileName + ' to `'  + ds + '`: ' + err);
    }
  }
}

will not merge configs if "db" key is not defined in the master file i.e. datasources.json.

So, I just modified the datasources.json to:

{
  "db": {}
}

and it worked!

Maybe it is my fault but the documentation is not clear enough.