Implementation Design for Notification Service

Implementation Architecture

The above figure  illustrates the components of notification service.Notification Service should be implemented with the following technical stacks:

Nodejs-Express (Typescript) 

Kafka Scheduler

Samza Processor

Sequence Diagram

Components Description

Notification Service contains the following blocks.

• Route Handler
• Middle-ware
• Service
• Kafka Producer Adaptor 
• Templates

Route Handler

Route handler receives the incoming request for a particular route and forwards it to service layer after validation.

Middleware

Middleware is responsible for validating the authorisation and  request data and should throw the error response if the request is invalid.

Service

Service part of notification scheduler  is responsible for pushing the request data as notification messages into the Kafka queue(to specific topic based on priority) and responding the client with appropriate success message.

Templates

Templates should be managed by Notification Service as local file or as the cloud file.Format of the template file should be json with following format:

[{
"name": "WELCOME_MSG",
"templateText": "Hi $firstName ,<p> welcome to Sunbird.Please <a href='$loginLink'>Click here</a> to login to your account.</p>",
"fields":["firstName","loginLink"],
"mandatoryFields":["firstName","loginLink"]
}]

Samza Stream Processor

Samza Message Processor will read messages from Kafka queue and send them with appropriate broadcast adapters (email,sms etc).Also in-case of failures in sending message it will push that  back into Kafka`s failed topics after maximum number of retries or message expiry.

API Specs

To create a notification through notification service client should make the request in following format:

POST notification/v1/create
{
"request":
  {"recipients":["recipient_1@domain.com","recipient_2@domain.com","recipient_N@domain.com"],
   "broadcastType":"email",
  "templateName":"WELCOME_EMAIL",
  "messageData":[{"data1":"recipient_1"},{"data1":"recipient_2"},{"data1":"recipient_N"}],
  "priority": "normal" // "immediate" ,"normal"
  "expiry" : "1543395622"
  }
}

Response

 Success 

{
  "id": "sunbird.notification.create",
  "ver": "v1",
  "ts": "2018-11-28 14:25:10",
  "params": {
    "resmsgid": null,
    "msgid": "",
    "err": "",
    "status": "success",
    "errmsg": null
  },
  "responseCode": "OK",
  "result": {
    "id": "96ec6fa4-e8d5-4c43-b8c8-0e2dea2cd77f"
  }
}

 Error  

{
  "id": "sunbird.notification.create",
  "ver": "v1",
  "ts": "2018-11-28 14:27:37",
  "params": {
    "resmsgid": null,
    "msgid": "",
    "err": "REQUIRED_PARAMS_MISSING",
    "status": "REQUIRED_PARAMS_MISSING",
    "errmsg": "messageData is required"
  },
  "responseCode": "CLIENT_ERROR"
}