/REST-API-Cassandra-Backend

A demo in utilizing Cassandra for persistent data store for a simple NodeJS Express API server. Express-Cassandra is used as an ORM for data handling.

Primary LanguageJavaScriptMIT LicenseMIT

REST-API-Cassandra-Backend

A simple REST API implementation using Express NodeJS with Cassandra for persistent data. Express-Cassandra is used as a Cassandra ORM for data handling.

Prerequisites

  • Ensure that you have [Cassandra] installed.
    • Homebrew is recommended for Mac 
      brew install cassandra
  • Ensure you have Cassandra query language shell installed 
    pip install cql
  • Ensure you have NodeJS installed.

Getting Started

  1. Clone the repository and navigate to it. 
    git clone https://github.com/Q-gabe/REST-API-Cassandra-Backend.git
cd REST-API-Cassandra-Backend

Cassandra Database

  1. Launch Cassandra. 
    cassandra
  2. Enter Cassandra Query Language Shell (cqlsh). 
    cqlsh
    (If you have issues with this step, check the Troubleshooting Errors section)
  3. Enter the following command 
    SOURCE './database/init.cql'
    (Ensure you are in the repository directory)

API Server

  1. Launch the server.

    yarn run start

  2. You can now access endpoints as detailed by the API routes section.

Clean up

  1. Stop Cassandra. 
    ps -ax | grep -i cassandra | awk '{print$1}' | xargs kill -9
  2. Stop the API server using Ctrl+C

API Routes

Route Name URL HTTP Verb Description
list /api GET Shows all pets information.
create /api/ POST Creates a pet information entry.
show /api/:name GET Shows a specific pet's information.
update /api/:name PUT Updates a pet's information.
remove /api/:name DELETE Remove a pet's information.

Troubleshooting Errors

If you see errors like this:

[0.001s][warning][gc] -Xloggc is deprecated. Will use -Xlog:gc:/usr/local/Cellar/cassandra/3.11.8/libexec/logs/gc.log instead.
intx ThreadPriorityPolicy=42 is outside the allowed range [ 0 ... 1 ]
Improperly specified VM option 'ThreadPriorityPolicy=42'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

This is because Cassandra in its current stable release at 3.11.8 only works with Java 8. (You can check your current Java version by running java -version).

Here's how to fix it:

# Install OpenJDK Java Version 8
brew tap homebrew/cask-versions
brew cask install homebrew/cask-versions/adoptopenjdk8
# Check if "AdoptOpenJDK 8" is present in your JVMs.
/usr/libexec/java_home -V
# Switch to JDK 8
export JAVA_HOME=`/usr/libexec/java_home -v 1.8`
# To return to your original JDK version, replace ORIGINAL_VERSION with original version number
export JAVA_HOME=`/usr/libexec/java_home -v ORIGINAL_VERSION`

Because export works only on the current shell, to avoid adding the change in java version to PATH, please use the terminal where you exported JAVA_HOME to launch Cassandra.

Design Decisions

  • Note that Cassandra is designed to be a query first columnar database, intended to scale across a highly distributed system with extremely large amounts of data and with availability as a top priority as opposed to data consistency. Do consider this in your own applications as this is merely a learning example.
  • Express-Cassandra does not currently support Typescript. If this is a concern, you can simply avoid implementing the ORM.