loopbackjs: Attach a model to different datasources

Question

I have defined several models that use a Datasource \"db\" (mysql) for my environment.

Is there any way to have several datasources attached to those models, so I wo

Answer 1

For anyone still looking for a working answer to this, the solution for switching databases on the fly was to write a middleware script that examined the request path and then created a new DataSource connector, passing in a variable based on the req.path variable. For example, if the request path is /orders, then "orders" as a string would be saved in a variable, then we attached a new Datasource, passing in that variable for "orders". Here's the complete working code.

'use strict';

const DataSource = require('loopback-datasource-juggler').DataSource;
const app = require('../server.js');

module.exports = function() {
  return function datasourceSelector(req, res, next) {
  // Check if the API request path contains one of our models.
  // We could use app.models() here, but that would also include
  // models we don't want.
  let $models = ['offers', 'orders', 'prducts'];
  // $path expects to be 'offers', 'orders', 'prducts'.
  let $path = req.path.toLowerCase().split("/")[1];

  // Run our function if the request path is equal to one of
  // our models, but not if it also includes 'count'. We don't
  // want to run this twice unnecessarily.
  if (($models.includes($path, 0)) && !(req.path.includes('count'))) {
    // The angular customer-select form adds a true value
    // to the selected property of only one customer model.
    // So we search the customers for that 'selected' = true.
    let customers = app.models.Customer;
    // Customers.find() returns a Promise, so we need to get
    // our selected customer from the results.
    customers.find({"where": {"selected": true}}).then(function(result){
      // Called if the operation succeeds.
      let customerDb = result[0].name;
      // Log the selected customer and the timestamp
      // it was selected. Needed for debugging and optimization.
      let date = new Date;
      console.log(customerDb, $path+req.path, date);
      // Use the existing veracore datasource config
      // since we can use its environment variables.
      let settings = app.dataSources.Veracore.settings;
      // Clear out the veracore options array since that
      // prevents us from changing databases.
      settings.options = null;
      // Add the selected customer to the new database value.
      settings.database = customerDb;
      try {
        let dataSource = new DataSource(settings);
        // Attach our models to the new database selection.
        app.models.Offer.attachTo(dataSource);
        app.models.Order.attachTo(dataSource);
        app.models.Prduct.attachTo(dataSource);
      } catch(err) {
        console.error(err);
      }
    })
    // Called if the customers.find() promise fails.
    .catch(function(err){
      console.error(err);
    });
  }
  else {
    //  We need a better solution for paths like '/orders/count'.
    console.log(req.path + ' was passed to datasourceSelector().');
  }
  next();
  };
};