oe-cloud

Introduction
oeCloud overall modules
oeCloud Features and functionalities
oeCloud API Documentation
oeCloud Difference between old and new

Introduction

oeCloud framework has been in development for almost two years and several developers for the first time worked on framework development. It has been adopted by many application developers so far and is being popular within Infosys and EdgeVerve. It has been demonstrated that application development using oeCloud is fast and developer get many levers to play with when he/she developing with oeCloud - due to framework offering and also JavaScript inherent power.

However, there is scope of improvement.

oeCloud itself has got several features and all of these features are bundled into single monolith node module. This causes trouble for application developer as many of features are included even though they are not needed by application developer.
Maintainability of oeCloud framework is getting difficult because features cannot be developed/enhanced in isolation.
Development cycle time is increased due to several CI/CD issues.
some of the node modules of loopback is forked and maintained by oeCloud team. Example is loopback-datasource-juggler. This node module is extensively modified and hence there is no way oeCloud can use latest loopback framework. This is tightly coupled with oeCloud.

To address above concerns, oeCloud is being modularized

oeCloud application will install oeCloud modules based on requirements. For example if data personalization is really required, he/she will install and use oe-data-personalization node module.
node modules will be created based on feature of oeCloud and each feature thus will have its own development life cycle.
This way, each feature will live independently of each other and will have separate CI / CD.
As each feature is separately developed - there will be decoupling with loopback, oeCloud can keep pace with loopback development.

oe-cloud is base node module for all oeCloud base application development.

oe-cloud overall modules

oeCloud Features and functionalities

This is most important project of oeCloud. This module needs to be required in application's server.js. Below are responsibilities of oe-cloud

oeCloud What it will do

Define BaseEntity Model
load modules described in app-list.json in sequence.
call init method of each module described in app-list.json
provide API for other modules to defined observer hook - and this module will call those hooks when application is loaded
ensure execution of loading and attaching mixin/middleware/boot script in each module of app-list.json while maintaining sequence
by default, oe-cloud will attach all the mixins defined in node module to BaseEntity unless it is specified otherwise.
ensure of loading of models defined in app-list module
expose loopback like APIs for application developer (eg app.boot(), app.start() etc)

app-list

This is basically javascript array of objects that contains list of node_modules that oe-cloud should load as part of application start up. This usually is JSON file with name as app-list.json. However, to achieve programmability, this can be also .js file like app-list.js. Another small improvement is, application developer can maintain different app-list for different environments which is based on NODE_ENV environment variable. If all sources (app-list.json, app-list.js and app-list.<NODE_ENV>.js) exist, oe-cloud will merge these objects. Typical app-list.json, which would be part of application would look like

[
  {
    "path": "oe-cloud",
    "enabled": true
  },
  {
    "path": "oe-module",
    "enabled": true
  },
  {
    "path": "oe-common-mixins",
    "enabled": true
  },
  {
    "path": "oe-validation",
    "enabled": true
  },
  {
      "path": "./",
      "enabled": true
  }
]

Usage

Typically, following code can be written in oeCloud application's server/server.js file

var oecloud = require('oe-cloud');

oecloud.boot(__dirname, function(err){
  oecloud.start();
})

Above code should able to start application. you don't have to do require of loopback or any of it's component.

oeCloud Models

BaseEntity

BaseEntity model is part of this module. Mixins in app-list.json modules will be attached to BaseEntity model - as described below. Most of the times, application models will be directly or indirectly derived from BaseEntity. Therefore, all functionalities of BaseEntity model is available to derived model.

ModelDefinition

ModelDefinition model stores metadata of all models in database. It will further opens up REST end point for client to get metadata of models and also can be used for runtime creation of new model.

Initialization

Note : There is possibility of loading oe Modules automatically. But having explicitly specified in app-list.json can be better idea and there is no ambiguity.

oe-cloud interacts with node modules defined in app-list.json in very specific, predefined way. Below are specifications

if your node module needs to be loaded, you MUST include that in app-list.json file. For example above oe-data-personsalization module will be loaded from /node_modules/oe-data-personalization folder
oe-cloud will call .init() method - IF DEFINED - after loading the module. Typically, you can create index.js file which will be loaded and init() will be called.
If init() is not defined, and you are exporting function as below, that function will be called

module.exports = function(app){
    // oe-cloud will call this function when it loads the module and when init() is not defined.
    // app object will be passed which has got much of information to manipulate
    // you can set observer hook as below

    app.observe('loaded', function(ctx, next){
        //ctx.app will have app handle
        return next();
    });
}

Observers

There are two observers provided.

loaded

When programmer calls boot, this even is fired to indicates options parameter is prepared. This options parameter will be used to pass to loopback boot. This includes list of all Models, Mixins folders, middleware and so on. Programmmer has opportunity to inspect / change this parameter.

boot-instructions-prepared

oeCloud boot is two step process. Based on options passed, it prepares instructions. That is first step and then in second steps it executes instructions. By hooking into this observer, programmer has opportunity to inspect and change instructions. This is useful when programmer wants to change behavior of model. For example, programmer may want to apply mixin on some model, or add property to model. Remember, model at this point is not created. At this point, you are just modifying instructions.

oecloud.observe('boot-instructions-prepared', function (ctx, next) {
  var models = ctx.instructions.models;
  var literalModel = ctx.instructions.models.find(function(item) { return item.name === "Literal" ;})
  literalModel.definition.mixins["SomeMixin"] = true;
  return next();
})

Note that, mixins are not applied to BaseEntity by default.

Loading Models

oe-cloud can load models defined in app-list.json's node_module.

you need to define model-config.json in your modules server and have path specified for models as below.
If you don't specifiy model-config.json, application needs to specify path to models folder in app's model-config.json.
You don't have to define Models in model-config.json. Only path is enough. However, in that case, application's model-config.json must have model entry otherwise, model will not be attached to datasrouce.
If in node_module's model-config.json, if you have defined dataSource (as shown below), it must exists otherwise error will be thrown.
If in node_module's model-config.json, you have defined dataSource or public property, these properties can be overriden in application's model-config.json. So in below example, application can change datasource of MyModel by having entry in it's own model-confg.json.

{
  "_meta": {
    "sources": [
      "../common/models"
    ],
    "mixins": [
      "../common/mixins"
    ]
  },
  "MyModel" :{
     "public" : true,
     "dataSource": "db",
  }
}

In above model-config, MyModel will be created as public model. However, definition of the model (.json) should be located in common/models folder of module. so in case of data personalization node module, my-model.json file should be present in /node_modules/oe-data-personalization/commmon/models folder

Attaching mixins

oeCloud will load mixins of node_modules defined in app-list.json. However, practically it will not attach these mixins to BaseEntity. But in reality it will attached to BaseEntity with value false. With value false, it will have no effect and mixin will not be attached to BaseEntity. But it ensures that mixin is loaded.
as in above case, mixins can be defined in node_modules's common/mixins folder. mixin's .js file will be loaded and attached to BaseEntity model by default with value false. Therefore, mixin will not be executed - but only loaded.
Application developer can turn off or turn on mixin in app-list.json as below.

  "OeSomeModule" : {
      "enable" : true,
      "mixins" : {
          "MixinA" : false,
          "MixinB" : true
      }
  }

Above example will change default behavior.
As mixins residing in module are attached to BaseEntity by default with value false, Module Developer can also change this specific default behavior by letting oe-cloud know about it. This can be done in _meta property of model-config.json of module. For example below entry will make MixinA not to attached to BaseEntity, while MixinB will be attached to BaseEntity with object having options { a:1, b:2 }

  "_meta": {
    "sources": [
      "../common/models"
    ],
    "mixins": [
      "../common/mixins"
    ],
    "mixinProperties"  : [
      {"MixinA" : false },
      {"MixinB" : {"a" : 1, "b" : 2} }
    ]
  },

As said earlier, by defualt node modules mixins are not attached to BaseEntity by default. This behavior can be changed by autoEnableMixins for node module. See example below of app-list.json

  "OeSomeModule" : {
      "enable" : true,
      "autoEnableMixins" : true
  }

above setting will ensure that all mixins of OeSomeModule are attahced to BaseEntity and therefore attach to all models derived from BaseEntity.

you can also selectively ON/OFF the mixin attachments by calling addModuleMixinsToBaseEntity API as below. This can be important if you have to have some mixins from other dependent module.

var oecloud = require('oe-cloud');
oecloud.addModuleMixinsToBaseEntity('oe-data-personalization', false);
oecloud.boot(__dirname, function(err){
  oecloud.start();
})

As shownn above, data personalization mixins will not be attached to BaseEntity by default. In this scenario, you will have to explicitly attach mixin with another API attachMixinsToBaseEntity

var oecloud = require('oe-cloud');
oecloud.addModuleMixinsToBaseEntity('oe-data-personalization', false);
// adding mixin with name of mixin explicitly. Thus not all mixins in data personalization modules are attached.
oecloud.attachMixinsToBaseEntity('DataPersonalizationMixin');

oecloud.boot(__dirname, function(err){
  oecloud.start();
})

you can also set mixin value in app-list.json to set default behavior of mixin

  ,
  {
    "path": "oe-validation",
    "ModelValidationMixin" : false,
    "enabled": true
  },

you can also change behavior programatically by setting mixin ON/OFF on specific module. Plesae see observers section of document.

Boot scripts

app-list.json's node module can have boot scripts defined in server/boot folder
oeCloud executes boot scripts in order same as modules are defined in app-list.json.
Thererfore, boot scripts in first module of app-list.json will be executed first.
However in each module, boot scripts are executed in alphabetical sequence. Therefore, if in module, there are two boot scripts, a.js and b.js, a.js will be executed first.
You will not interfere the order of boot scripts in other modules.
Each boot script will take two parameters, app and callback. if you don't use callback, then boot script will be executed in sync way.

// boot script with callback
module.exports = function(app, cb){

    // must call cb() otherwise next boot script will not be executed
    // should throw error if needed like
    // return cb(new Error("something went wrong");
}

// boot script without callback
module.exports = function(app){

    // next boot script will be executed when function returns
}

Middlewares

oeCloud would merge all middlewares in all modules defined in app-list.json and ensure execution of middleware. Each middleware should have entry in respective module's middleware.json file.

Middleware should have entry such as below in middleware.json of module's server folder.

session:before": {
        "./middleware/populate-context-from-scope": {},
        "./middleware/populate-context-from-headers": {}
        }

and middleware should have code such as below. This file should reside in server/middleware folder of your node_module.

module.exports = function (options) {
  return function(req, res, next) {

      return next(); // must call next() otherwise next middlware will not be executed and system will hang.
  }

}

Model Customization

Typically, oeCloud based application would have its own models to fulfill business requirements. For example, there would model name Customer that can be used to handle Customer entity. It would help store customer data in actual database table customer and also expose REST API for Customer. When such application or product is to be delivered to client, client would want changes to this default implementation of existing Customer model. Those changes could be

adding new properties, hiding existing properties or changing types of existing properties
adding new mixin
adding JS file to customized model

As a developer, all of above changes can be done in customization model. Customization module is nothing but regular node_module. This node_module can be loaded into application by specifing it in app-list.json. oeCloud framework would load these modules in sequence of app-list.json. As a customization developer, you need to add your customized module entry into app-list.json

  {
    "path": "product-customization-module",
    "enabled": true
  },

You can create any new models in customization module of yours and if they are mentioned in model-config.json of your module, those models will be loaded in application.

However, if you want to customize any model, you need to add extra property named customModel in model-config.json for customized model entry as shown below.

  "Customer": {
    "dataSource": "db",
    "public": true,
    "customModel" : true
  },

customModel flag would help identify oecloud framework that you want to customize Customer model. oeCloud framework then merge your customization with original model.

You can also have customer.js file which is then loaded and also you can have mixin.

Note : More importantly exports function all .js files of models are executed in sequence. There should not be any extra executable code apart from that inside module.exports () function.

Call Context and options

Options

When we are referring to options, we are referring to second parameter usually we pass to model.find() or model.create() functions. This options parameter flows throughout the loopback pipeline. That is all observer hooks will get context in which it has this options parameter.

model.find({where : {id :  "a"}}, {ctx : {somefield : "X"} }, function(err, data){
 // results are returned in data
});


model.observe('access', function(ctx, next){

  assert(ctx.options.somefield === 'X')
    
})

This is all good when find() is being called by programmer from javascript code. However when find() is called due to http GET request on model, options parameter is parepared in oe-cloud module. specifically lib/warpper.js's _newCreateOptionsFromRemotingContext() is used to build this options.

options has got most important property ctx. All other properties are not touched by oecloud framework.

This property is now built by http request's callContext.ctx property and basically both are actually same.

therefore if the request object is req and options object is options then

  assert(req.callContext.ctx === options.ctx);

With above design, if you change callContext.ctx property in middleware, that will be directly reflected in options.ctx property

callContext

callContext property of HTTP request is created by oeCloud framework in one of it's middleware. As said above callContext.ctx is same as options.ctx. you must break this link. With this link if you modify callContext.ctx in middleware or before remote hooks, it will be available in options.ctx field in your observer hooks.

Same way, if you change options.ctx in observer hooks, you will see that in after remote hook.

  model.beforeRemote( '**', function( ctx, opts, next) {
    
    ctx.req.callContext.someField = 'x';
    
    next();
  });
  
  
  model.observe('before save', function(ctx, next){
    assert(ctx.options.ctx.someField === 'x');
    
    ctx.options.ctx.otherField = 'y'
    
    // never do this as it will break link ---->>> ctx.options.ctx = { otherField : 'y', someField : 'x' }
  });

  model.afterRemote( '**', function( ctx, opts, next) {
    
    assert(ctx.options.ctx.otherField === 'y');
    
    next();
  });

oeCloud API Documentation

Common Utility API

There are simple utility functions which can be used in your module

IsBaseEntity(Model)

This utility function checks if given Model is derived from BaseEntity. This will be useful many times in programming. Below is code snippet.

const oecloudUtil = require('oecloud/lib/util');
const loopback = require('loopback');
var customerModel = loopback.findModel('Customer')
console.log("Customer Model is derived from BaseEntity ", oecloudUtil.isBaseEntity(customerModel));

mergeObjects(obj1, obj2)

This function merge two objects. Below is usage and examples. Developer can use lodash libray for that also.

const util = require('oecloud/lib/util');

var o1 = { a : "a" };
var o2 = { b : "b" };
var o = util.mergeObjects(o1, o2);
// { a: "a", b : "b" }

var o1 = { a : "a" , c : { d : { e : "e" } } };
var o2 = { b : "b" };
util.mergeObjects(o1, o2);
//  { a : "a" , b: "b", c : { d : { e : "e" } } };


var o1 = { a : "a" , c : { d : { e : "e" } } };
var o2 = { a : "b" };
util.mergeObjects(o1, o2);
//  { a : "b" , c : { d : { e : "e" } } };

var o1 = { a : [1,2,3] , c : { d : { e : "e" } } };
var o2 = { a : [2,4,5] };
util.mergeObjects(o1, o2);
//  { a : [1,2,3,4,5] , c : { d : { e : "e" } } };

checkDependency(app, modules)

This function checks if all modules in app-list satisfies depenency.

isInstanceQuery(Model, where)

This function checks if this is instance based query where primary key of Model is part of where clause. For nesting, it looks only and clause.

const utils = require('oecloud/lib/util');
utils.isInstanceQuery(newCustomerModel, { where: { name: 'x' } }); // false
utils.isInstanceQuery(newCustomerModel, { where: { and: [{ name: 'x' }, { id: 1 }] } }); // true
utils.isInstanceQuery(newCustomerModel, { where: { and: [{ name: 'x' }, { age: 1 }, { and: [{ id: 1 }, {age : 10}]}] } }); // true
utils.isInstanceQuery(newCustomerModel, { where: { and: [{ name: 'x' }, { age: 1 }, { or: [{ id: 1 }, {age : 10}]}] } }); // false

getIdValue(Model, data)

This function gives you id value in your data.

const utils = require('oecloud/lib/util');
var id = utils.getIdValue(CustomerModel, { id: 10, name: "A" }); // id = 10
var id = utils.getIdValue(CustomerModel, { name: "A" }); // id = undefined

idName(Model)

Returns id field name of the model. By default "id"

const utils = require('oecloud/lib/util');
var idName = idName(CustomerModel); // returns  "id"

Application API

These are the APIs are made available on application object of oeCloud. These APIs mostly should be called before boot.

setServer(server)

This function will allow application to set http or https server. This way, creating of server can be controlled by application. By default oeCloud will create http server.

const oecloud = require('oe-cloud');

var server = require('http').createServer(oecloud);
oecloud.setServer(server);

boot(__dirname, cb)

This function will boot the application. It will do following typical things, but not limited to that.

Load all models, mixins, middleware, boot scripts etc from modules in app-list.json
Merge configuratino like model-config.json.
Create ModelDefinition entries for all the models of system. Also loads and creates model based on ModelDefinition.
executes boot scripts in sequence on app-list. Scripts in given module are executed by order of name alphabatically. Therefore, a.js will be executed before b.js.

const oecloud = require('oe-cloud');
oecloud.boot(__dirname, function(err){
  orcloud.start();
})

start()

This function will start web server and starts listening on PORT. Default port is 3000, or it can be set by PORT environment variable. This function will emit application start event 'started' that application can listen on.

const oecloud = require('oe-cloud');
oecloud.start()
oecloud.once('started', function(){
   // do something.
});

addContextField(name, property)

This function adds context parameter to AccessToken. That way, if this field is set during creation of access token, it will be made avaialble throughout the application context.

const oecloud = require('oe-cloud');
oecloud.addContextField('tenantId', {
  type: "string"
});

accessToken.evObserve("before save", function (ctx, next) {
  ctx.instance.tenantId = findTenantIdForUser(ctx.instance.userId);
  return next();
});


// after above code is done during start up of application, "tenantId" is available throughout context

customerModel.evObserve("access", function(ctx, next){
    var context = ctx.options.ctx;

    assert (context.tenantId)
})

customerModel.beforeRemote("*", function(req, res.next){
    var context = req.callContext;

    assert (context.tenantId)
})

removeForceId

This function on app object can be used to remove ForceId of models which are not derived from BaseEntity. User, Role and RoleMapping are typical models, which are not derived from BaseEntity and you want to remove ForceId setting.

var app = require('oe-cloud');
    app.removeForceId('User');
    app.removeForceId('Role');
    app.removeForceId('RoleMapping');

However, please note that, by default above code is executed as part of boot script. Meaning, by default, ForceId is deisabled for User, Role and RoleMapping models. Therefore, you can create User/Role/Rolemapping data by passing id field explicitly. If you want to disable this, you can use disableForceIdForUserModels setting to true in config.json.

About ForceId : In loopback 3, ForceId setting is done on model which is true by default. In this case, user/programmer cannot create a record on model by passing his/her own id. Id is always generated by loopback. To disable this setting, you can use removeForceId call.

setACLToBaseEntity

This function should be called to set default ACL on BaseEntity Model. in oeCloud 2.x, BaseEntity doesn't have any ACL applied. Therefore, all operations on all models which are derived from BaseEntity are possible. To prevent that, programmer can call this method.

var oecloud = require('oe-cloud');
oecloud.setACLToBaseEntity({
  "accessType": "WRITE",
  "principalType": "ROLE",
  "principalId": "$unauthenticated",
  "permission": "DENY"
  });
// oecloud.boot() and other code

Remember that this has to be done before other models are loaded - meaning it should be done before you call boot().

observers

As a programmer, you can implement oeCloud observer hooks. The most important hook is 'loaded'. you can use code similar to following to create the observer hook. 'loaded' observer is executed when all modules in app-list.json is loaded. you can change some configuration, add or remove mixins before boot gets executed.

    app.observe('loaded', function(ctx, next){
        //ctx.app will have app handle
        return next();
    });

Configurations

Name	Default	comment
disableAboutMe	false	AboutMe API is exposed and any authenticated user can call /api/users/aboutme to know about logged in user
disableDefaultAuth	false	Authentication mechanism is enabled by default. you can set this value to true to disable it
enableAuthCookie	false	You can enable Auth cookie to be sent when user login using /api/users/login API. By default it is disabled
enableForceIdForUserModels	false	ForceId is disabled for Users/Role/RoleMapping models. You can enable it to keep default loopback behavior

Remote End point (RestAPI)

aboutMe

Logged in user can know about him/herself by calling this API. API signature is shown below. If auth cookie is enabled, you don't have to pass access_token if you are using browser.

GET
http://localhost:3000/api/users/aboutme?access_token=<youraccesstoken>

Add fields to BaseEntity or ModelDefinition

If you want to add (change) schema of BaseEntity or ModelDefinition, you can do so by provided API as shown below.
Typically, you will write observer hook and call method provided by app. For example, below, _version property is added to ModelDefinition model.
Also you can see BaseEntity will start having autoscope field with 'tenantId' as value.

var app = require('oe-cloud');
app.observe('loaded', function(ctx, next){
  app.addSettingsToModelDefinition({properties : {_versioning : {type : "boolean", default : false}}});
  app.addSettingsToModelDefinition({properties : {HistoryMixin : {type : "boolean", default: false}}});

  app.addSettingsToBaseEntity({autoscope:["tenantId"]});

  return next();
})

oeCloud Difference between old and new

Feature	Exisiting	Proposed
Custom Types Register-Email & timestamp	Data Source juggler Change	Model Builder Wrapper oe-cloud
after access observer notification	DAO Change	Data Source juggler Wrapper oe-cloud
app-list.json handling	server.js	oe-cloud
EvObserver	Mixin in file	oe-cloud
Audit Field	Mixin in file	oe-common-mixins
Versioning	Mixin in file	oe-common-mixins
History	Mixin	oe-common-mixins
Idempotency	Mixin+DAO	Not done
Soft Delete	Mixin + DAO	oe-common-mixins
Validations	Mixin	oe-validation
Expression Support	Mixin	oe-expression
Model Composite - Implicit and Explicit	DAO Change	DAO Wrapper oe-model-composite
Data Personalization	Mixin	oe-personalization
Service Personalization	Mixin+Boot	Boot oe-service=personalization
Cachinge	Mixin+DAO	DAO Wrapper oe-cache

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