Multi-Tenant Mongoose Model Wrapper For NodeJS Based Applications

multi-tenant.js

import mongoose, { Schema } from 'mongoose'
import { getCurrentTenantId } from './storage'

/**
Function will return another function, which will further return a mongoose discriminator.
The only difference here is that everytime you use the mongoose model, you will have to call a function,
but it will give you a freedom of passing tenant-based data. 
*/
export function tenantModel(name, schema, options) {
  return (props = {}) => {
    // add new props to the schema
    schema.add({ tenantId: String })
    
    // create a mongoose model
    const Model = mongoose.model(name, schema, options)

    const { skipTenant } = props
    // getCurrentTenantId() is a function will returns current tenant
    // this function uses continuation-local-storage npm package
    const tenantId = getCurrentTenantId()
    
    // if no tenant or you want to skip tenant specific descrimintor, return actual model
    if (!tenantId || skipTenant) return Model
    
    // set the descriminatorKey for the model
    Model.schema.set('discriminatorKey', 'tenantId')
    
    // set the descriminator name
    const discriminatorName = name + '-' + tenantId
    
    // check if a descriminator already exists
    const existingDiscriminator = (Model.discriminators || {})[discriminatorName]
    
    // if it does exist, simply return that. Otherwise create new
    return existingDiscriminator || Model.discriminator(discriminatorName, new Schema({}), `${tenantId}`)
  }
}

// this function will return simple model,
// so that you write the consistent code like calling the Model function to access the model
export function tenantlessModel(name, schema, options) {
  return () => mongoose.model(name, schema, options)
}

storage.js

import { createNamespace } from 'continuation-local-storage';

// define namespace name
const namespaceName = 'request';

// create namespace instance
const ns = createNamespace(namespaceName);

// export function to bind current namespace to the req and res
export function bindCurrentNamespace(req, res, next) {
  ns.bindEmitter(req);
  ns.bindEmitter(res);

  ns.run(() => {
    next();
  });
}

// export function to set tenantId for current request being processed
export function setCurrentTenantId(tenantId) {
  return ns.set('tenantId', tenantId);
}

// export function to get previously set tenantId of request
export function getCurrentTenantId() {
  return ns.get('tenantId');
}