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Shopping Cart API Assignment

Overview

  • A storage system for Shopping Cart data, and an API to access the data written purely in Python
  • Features developed are Leaderless replication, data partitioning, eventual consistency
  • Used CRUSH hash function for mapping, Zookeeper for coordination, read-repair using version vectors for consistency, Flask to build the API

Problem Statement Breakdown

  • Architecture

arch

  • Schema Design

sc

  • Database nodes API design

    • Database used in each node - TinyDB.
    • Endpoints provided
      • GET /productslist
        • Returns the list of products present in that node
      • GET /product
        • Takes as query parameter, the name of the product, and returns its quantity and version
      • POST /product
        • Takes product's name, quantity and version as input, and updates the information in the database
      • GET /userslist
        • Returns the list of users present in that node
      • GET /user
        • Takes as query parameter, the email of the user, and returns its cart and version
      • POST /user
        • Takes user's email and version as input, and updates the information in the database
      • POST /addtocart
        • Takes user's email, cart and version as input, and updates the information in the database

  • Database Node Architecture

    • Registers itself to zookeeper, with its IP and flask app port number as data
    • Starts the database API

  • Gateway API design

    • Endpoints provided
      • GET /productslist
        • Calls GET /productslist for each database node registered in zookeeper, returns union of the lists.
      • GET /product
        • Takes as query parameter, the name of the product
        • Internally hashes it to an integer
        • Finds the mapping of the value to the nodes from CRUSH hash function using read quorum of (number of nodes + 1)/2
        • Calls GET /product on each node found above
        • Checks if some data is stale (version number != latest version)
        • Performs read-repair if required, takes the minimum of quantities of all latest versions as the latest value
        • Returns the latest quantity and version back.
      • POST /product
        • Takes product's name and quantity as input
        • Internally hashes it to an integer
        • Finds the mapping of the value to the nodes from CRUSH hash function using read quorum of (number of nodes + 1)/2
        • Calls GET /product on each node found above
        • Checks if some data is stale (version number != latest version)
        • Performs read-repair if required, takes the minimum of quantities of all latest versions + the quantity present in the request as the latest value
        • Calls POST /product on each node found from CRUSH hash function with the latest data
      • GET /userslist
        • Calls GET /userslist for each database node registered in zookeeper, returns union of the lists.
      • GET /user
        • Takes as query parameter, the email of the user
        • Internally hashes it to an integer
        • Finds the mapping of the value to the nodes from CRUSH hash function using read quorum of (number of nodes + 1)/2
        • Calls GET /user on each node found above
        • Checks if some data is stale (version number != latest version)
        • Performs read-repair if required, takes the maximum of quantities of each product in cart among all the latest versions
        • Returns the latest cart and version back.
      • POST /user
        • GET /userslist
        • Calls GET /userslist for each database node registered in zookeeper, returns union of the lists.
      • GET /user
        • Takes as query parameter, the email of the user
        • Internally hashes it to an integer
        • Finds the mapping of the value to the nodes from CRUSH hash function using read quorum of (number of nodes + 1)/2
        • Calls GET /user on each node found above
        • Checks if some data is stale (version number != latest version)
        • Performs read-repair if required, takes the maximum of quantities of each product in cart among all the latest versions
        • Returns the latest cart and version back.
      • POST /createuser
        • Takes user's email as input
        • Internally hashes it to an integer
        • Finds the mapping of the value to the nodes from CRUSH hash function using read quorum of (number of nodes + 1)/2
        • Calls POST /createuser on each node found from CRUSH hash function
      • POST /addtocart
        • Takes user's email and products and quantities to be added (cart) as input
        • Internally hashes email to an integer
        • Finds the mapping of the value to the nodes from CRUSH hash function using read quorum of (number of nodes + 1)/2
        • Calls GET /user on each node found above
        • Checks if some data is stale (version number != latest version)
        • Performs read-repair if required, takes the maximum of quantities of each product in cart among all the latest versions
        • Calls POST /addtocart on each node found from CRUSH hash function with the latest data

How to run

  • docker-compose up -d --scale dbnode=3

Demo

Access the demo video here

Group Members

Name ID
Harpinder Jot Singh 2017A7PS0057P
Vishal Mittal 2017A7PS0080P

Resources

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video

  • Above video is made using Visual Source