API Key handler

API Key handler using Node JS and Express (No DBMS is used). I was able to achieve this in O(lgn) Time Complexity 😁

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What is in here 🤔

1. Design
   1. Data Structures
   2. Functions
2. Setup
3. API
4. Tests

Design

apiGenHandler handler Class wraps all the required functions and data. Spawning a server will create a single apiGenHandler object which holds the data until the lifetime of the server. Finally wrapped with Express to act as a server.

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Data structures:

keys dictionary holds the below structure

keys: {
    "<API_KEY>": {
        "api": <API_KEY>
        "state": 0/1
        "ts": <Date Object>
    }
}

api: Holds the API Key

state: 0 for blocked and 1 for unblocked

ts: holds Date object

activeCount variable will be incremented whenever a new API key is generated and decremented when API key is deleted or pushed to block state. This is used to get the count of Unblocked API keys in O(1)

blockedQueue is a sorted set (which is actually a splay tree) making most of its operations done in O(log(n)) instead of O(n). This sorted list holds the "<API_KEY>" objects which are in blocked state and sorted by their timestamps.

activeSet is a sorted set (which is actually a splay tree) which holds the set of active or available API keys.

blockedQueueHandler is a boolean variable which is used to execute our killAPI function which is a long running block of code to continuously check blockedQueue and remove those which are expired

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Functions

genApiKey

Time Complexity: O(log(n)) - n is the number of keys
Return: True if it is successful else false

Generates a random API key. I am using crypto node module to generate a 32 Byte => 256 bit random value and converting that to a hexadecimal value. Adds the active API key to the activeSet which will be used during random choosing in O(lgn) time and increment activeCount for getting the count in O(1). Sets the state of the API key in O(1).

getAvailableAPIKey

Time Complexity: O(log(n)) - n is the number of keys
Return: API Key if it is successful else false

It checks for the activeCount variable to get the number of available API keys in O(1). Later it decrements activeCount. It chooses a random number between 0 and number of available API keys which we got earlier. We then access the API key from activeSet in O(log(n)) time and delete the Key within the same time complexity. Further we will change the state of the retrieved API key to 0 in O(1) time and will find a Date object adding 5 minutes to the present time to get the expiration time. Upon assigning the expiration time to ts key will add this object to the blockedQueue sorted set (where the sort is based comparing time stamps). We will then execute the killAPI function which will check the blockedQueue repeatedly to delete the keys after the expiration. Wrapping this withing a Promise object made it run asynchronously without abruptly the main process.

unblockAPIKey

Time Complexity: O(log(n)) - n is the number of keys
Return: True Key if it is successful else false

We change the state key to 1 and increment the activeCount and add the the key to the activeSet in O(lg(n)) and return.

deleteAPIKey

Time Complexity: O(log(n)) - n is the number of keys
Return: True Key if it is successful else false

It deletes the key irrespective of the state from the memory.

pollApiKey

Time Complexity: O(log(n)) - n is the number of keys
Return: True Key if it is successful else false

We change the ts key which is a Date object by incrementing it with more 5 minutes. So here we will delete the previous key from the blockedQueue in O(lg(n)) time and add it back in O(lg(n)) time with new ts which will ultimately equivalent to pushing the key to the bottom of the queue.

killAPI

Time Complexity: O(log(n)) - n is the number of keys

We run a infinite loop which keeps checking the blockedQueue for the expired time stamps and removes them accordingly. Wrapped it in Promise object so that it runs asynchronously without waiting for the function return.

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Setup

Clone the repository

$ git clone https://github.com/kmehant/API-Key-Handler-NodeJS.git

Install node modules

$ npm install

Start the server

$ node index.js

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API

Request GET /

description:
To ping the server

Request POST /key

description:
To generate an API key

Request GET /key

description:
To get an available API key

Request DELETE /key?api=

description:
To delete an API key

Request POST /key/unblock?api=<key>

description:
To unblock the given API key

Request POST /key/poll?api=<key>

description:
To poll to server for the given API key which extends expiry time by 5 minutes

Tests

Using Chai

npm test