mongoose-model-stream

a mongoose model generator with a change stream

info:

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Install

yarn add mongoose-model-stream

or

npm install --save mongoose-model-stream

How to Use

const moduleStream = require('mongoose-model-stream');

constructor

This moduleStream function takes two arguments.

• modelName: The name of the model
• schema : The schema definition of the model.

There is also an optional 3rd argument.

• options OR enableDownStream
  • options: the options object that will be passed to the change stream schema. You can set enableDownStream as a Property on options
  • enableDownStream: A boolean to change will create change events, without listening to the stream for updates. (Default: true)

const ChatSchema = new mongoose.schema({
  text: String
});

const Chat = moduleStream('Chat', ChatSchema);

Attached to Chat will be a .stream baced on RxJs. This will emit change events baced on rfc6902

The payload looks like:

Property	Type	Description
patchs	Array	Present for all changes to the item. - An array of rfc6902 operations.
target	String(ID)	The Unique identifier for the target Object
_id	String(ID)	The Unique identifier for this diff
createdAt	String(Date)	The time the chage was made
tag	String	A customisable identifier for this change
action	String(Enum)	This will be "CREATE", "UPDATE" or "DELETE" depending on the state of the document in the database
getChange	fn() ➜ Obj	an object with only the changes applied
getTarget	fn() ➜ promise ➜ doc	get the target document from the Database

model

Create

A new function will be added to the model

• saveBy : This is used the tag a change with who made it.

event.when = "today";
event.saveBy(user);

A saveBy id will be add to the change record

Outputted change

{ patchs:
   [ {
     op: 'add',
     path: '/when',
     value: 'today'
   } ],
  _id: '5a958d12fc413a44ac760fb1',
  target: '5a958d11fc413a44ac760fa9',
  saveBy: '5a95872c39c0be3afaeb9a86',
  createdAt: '2018-08-12T04:46:02.009Z',
  action: "UPDATE"
}

Update

• "saveBy" is also provided in the update function(s)
  • update, updateMany, updateOne, findOneAndUpdate, findByIdAndUpdate

You said the "saveBy" bypassing it in the "options" argument. This can be an ID of an object(String) that will be used for all patchs or a function to calculate the ID for each specific updated document

const conditions = {foo:true },
updateValues = {setBarTo:false},
options = {savedBy:(oldDoc,newDoc,patchs)=>oldDoc.user_id}
event.updateMany(conditions,update,options)

tag

A custom string denoting the change can be added to the following functions

• Create e.g. const event = await Module.create({ text:updateTextTag },{ tag :"FOO_1" })
• save e.g. event.save("FOO_2") or event.save({ tag :"FOO_3"})
• saveBy e.g. event.saveBy(user,"FOO_4")
• update e.g. Module.updateOne({_id},{$set:{text:"bar"}},{ tag : "FOO_5" })

---

run samples

node example/sample.js

Example

require('mongoose-model-stream');
const { Schema, moduleStream } = require('mongoose');

// create a schema
const ChatSchema = new Schema({ text: String }, { timestamps: true });

// create a module
const Chat = moduleStream('Chat', ChatSchema);

// subscribe to change events
Chat.stream.subscribe(console.log, console.error, console.info);

Chat.create({ text: "foo" })
    .then(function (chatMessage) {
        chatMessage.text = "bar";
 return chatMessage.save();
    }).then(function (chatMessage) {
        chatMessage.text = "baz";
        chatMessage.save();
    }).catch(console.error);

Output:

Change: 1

{ patchs:
   [ {
     op: 'add',
     path: '/text',
     value: :'foo'
   }, {
     op: 'add',
     path: '/_id',
     value: '5a86eea992f78d54f1cd65e9'
   }, {
     op: 'add',
     path: '/updatedAt',
     value: :'2018-08-12T04:46:01.993Z'
   }, {
     op: 'add',
     path: '/createdAt',
     value: '2018-08-12T04:46:01.993Z'
   }  ],
  _id: '5a86eeaa92f78d54f1cd65ea',
  target: '5a86eea992f78d54f1cd65e9',
  createdAt: '2018-08-12T04:46:02.009Z',
  action: "CREATE"
}

Change: 2

{ patchs:
   [ { op: 'test', path: '/updatedAt', value: '2018-08-12T04:46:01.993Z' },
     { op: 'replace', path: '/text', value: 'bar' },
     { op: 'replace', path: '/updatedAt', value: '2018-08-12T04:46:02.116Z' }, ],
  _id: '5a86eeaa92f78d54f1cd65eb',
  target: '5a86eea992f78d54f1cd65e9',
  createdAt: '2018-08-12T04:46:02.022Z',
  action: "UPDATE"
 }

Change: 3

{ patchs:
   [ { op: 'test', path: '/updatedAt', value: '2018-08-12T04:46:02.116Z' },
     { op: 'replace', path: '/text', value: 'baz' },
     { op: 'replace', path: '/updatedAt', value: '2018-08-12T04:46:02.342Z' }, ],
  _id: '5a86eeaa92f78d54f1cd65ec',
  target: '5a86eea992f78d54f1cd65e9',
  createdAt: '2018-08-12T04:46:02.122Z',
  action: "UPDATE"
 }