Ticketing App

A microservice architecture that provides services for buyers and sellers of tickets for sports, concerts, theater and other live entertainment events.

Features

• Production grade authentication service
• Sellers can list their tickets
• Sellers can update the price of the listed ticket
• Buyers are buy tickets
• Buyers will have a 15 minutes window to buy a ticket
• During that 15 minutes window no one can buy the ticket
• Handles the case when buyer buy the ticket and seller at the same time increases the price of the ticket
• Production grade payment service

Design

Here common refers to a npm custom build library by us, which will be shared with all the services

Tech Stack

• Next.js
• Node.js
• Express.js
• Mongodb
• Redis
• NATS
• Stripe.js
• Typescript

Services

• auth: Everything related to user signup/signin/signout
• tickets: Tickets creation/editing. Knows whether a ticket can be updated
• orders: Order creation/editing
• expiration: Watches for order to be created, cancels them after 15 minutes
• payments: Handles credit card payments. Cancels order if payments fails, completes if payment succeeds

Auth

Route	Method	Body	Purpose
api/users/signup	POST	{email: string, password: string}	Signup for an account
api/users/signin	POST	{email: string, password: string}	Signin to an existing account
api/users/signout	POST	{}	Signout of an account
api/users/currentuser	GET	-	Return info about the user

Schema

• User

  Name	Type
  email	string
  password	string

• Ticket

  Name	Type
  title	string
  price	number
  userId	Ref to User
  orderId	Ref to Order

• Order

  Name	Type
  userId	Ref to User
  status	Created, Cancelled, Awaiting payment, Completed
  ticketId	Ref to Ticket
  expiresAt	Date

• Charge

  Name	Type
  orderId	Ref to Order
  status	Created, Failed, Completed
  amount	number
  stripeId	string
  stripeRefundId	string

Events

• UserCreated UserUpdated
• OrderCreated OrderCancelled OrderExpired
• TicketCreated TicketUpdated
• ChargeCreated

GCP Integration

• when we make changes in the synced files
  
  
• when we make changes in the unsynced files
  
  

Error Handling!

• we will make two classes RequestValidationError and DatabaseConnectionError which will extend to the Error class and so that they can add custom features to the Error class like reason of the error and message to show regarding the error
• inside the error-handler middleware we will check if it is invoked due to the RequestValidationError or DatabaseConnectionError, and based on the error type it will send custom messages to the client
  

Error Response

• All error response that we send out from our server will have this structure

{
  errors: {
    message: string,
    field?: string
  }[]
}

Custom Errors Verification

• All the error classes like RequestValidationError and DatabaseConnectionError should contain a statusCode variable and a serializeErrors method.
• To ensure all error classes stick to the rule we will make a CustomError Abstract Class

NOTE: on abstract class
- cannot be instantiated
- used to setup requirements for subclasses
- when we compile TS to JS, we end up with a class definition in JS from abstract class in TS unlike an interface as it does not exist in JS 

Signup Flow

MongoDB User Collection

• Mongoose User Model represents the entire collection of users
• Mongoose User Document represents one single user
  
  

Auth Mechanism

• We will be using JWT with cookies for our auth mechanism
  
  
• Because we're using Next.js, we're conducting server-side rendering, which means that if we want the client's initial request to include a JWT token, we'll have to rely on cookies
  
  

Storing secrets in K8s cluster

• In our Kubernetes cluster, we build an object called secret that contains multiple key-value combinations and is shared across all pods through environment variables.
  
  
• Creating a secret object (imperative)

kubectl create secret generic jwt-secret --from-literal=jwt=asdf

Signin Flow

Current User Flow

• This route is used to check if the user accessing the resources is logged in
  
  

Testing

Workflow

Client

Component tree