Create file server/boot/subdomain.js and edit server/model-config.json to add "tenant": true property on every model. Only work with loopback-connector-postgresql and schema.

subdomain.js

'use strict';

var modelConfig = require('../model-config.json');

module.exports = function(app) {
  app.use(function(req, res, next) {
    // set tenant based subdomain or use public
    var subdomain = (req.subdomains.length > 1) ? req.subdomains.pop() : req.subdomains[0];
    var tenant = req.subdomains.pop() || 'public';

    // we go through all the model names from model-config.json
    Object.keys(modelConfig).forEach(function(modelName) {
      // validate if model have property tenant
      if (modelConfig[modelName].hasOwnProperty('tenant')) {
        // set postgresql schema for model
        app.models[modelName].definition.settings.postgresql.schema = tenant;
      }
    });
    next();
  });
};

i have same problem. I have 2 tenant with model user. If a user is logged in a tenant, other users are dislodged in other tenants