Email Scheduler

Its an email scheduler which will fire the mails to designated receivers on given time.

Tech Stacks required

• NodeJS v14.19.0 (Hapi.js as a framework)
• MongoDB

Features

• Create a scheduled job which will trigger the mail on given time.
• Get paginated report of created jobs.
• Get Details of a single job as well by just triggering an API.

Installation

Requires Node.js v14+ to run (v14.19.0 Preferred) and MongoDB .

set the Environment variables.

MONGO_URI= <mongodb uri>
MONGO_USERNAME= <mongodb username>
MONGO_PASSWORD=<mongodb pasword>
MONGO_DBNAME=EMAIL_SCHEDULER
HOST=0.0.0.0
PORT=8000
EMAIL_ID=<Senders Email ID>
EMAIL_PASSWORD=<Password for above Email ID>
SMTP_SERVER=<SMTP server of above email>
SMTP_PORT=<SMTP server port>

Install the dependencies and devDependencies and start the server.

npm i
node index.js

API documentation

Swagger documentation can be found on 0.0.0.0:8000/documentation

• POST /v1/jobs
  • payload:

    [
        { 
        "email":"email id of the receiver",
        "time": Valid: ["now/ x hour later/ on a particular time( Ex- 21st march,2022,6:00 AM)"],
        "subject":"Email subject",
        "body":"Email body"
        }
    ]

• GET /v1/jobs
  • query:

    page: Number
    limit: Number

• GET /v1/jobs/{id}
  • parameter:

    id: Mongo ObjectId of any job
    

How does it work?

• Works on the basis of a cronjob acting as a per-minute observer for any upcoming scheduled job.
• Each mail to be sent is created as a job by using POST API.
• Based on the time given in payload, the execution time is decided and set.
• Whenever observer finds a job whose execution time is less than current time and is not executed yet, will be fed to the executor.
• The executor will run each job asynchronously, it will trigger each mails, and updates the job status as success/failure
• A time will be stored, at which the job was executed.

Some clarifications

• DB like postgres/MySQL with read heavy efficient operations can be used.
• As MongoDB natively uses UTC timezone, the cron (Observer) also runs on the UTC timezone.
• The API responses also are returned in UTC timezones. The timezone can be changed on the client side.