round-robin-js

An implementation of the round robin as a data structure. The following strategies are implemented:

SequentialRoundRobin	selects the next item based on the order of insertion
RandomRoundRobin	selects the next item randomly
PriorityRoundRobin	selects the next item based on its priority

Contents

• Install
• require
• import
• API
  • constructor
  • add
  • next
  • count
  • deleteByKey
  • deleteByValue
  • reset
  • clear
• Build
• License

Install

npm install --save round-robin-js

require

const {
  SequentialRoundRobin,
  RandomRoundRobin,
  PriorityRoundRobin
} = require('round-robin-js');

import

import {
  SequentialRoundRobin,
  RandomRoundRobin,
  PriorityRoundRobin,
  RoundRobinItem // the internal item type
} from 'round-robin-js';

API

constructor

All types accept an initial list of values. PriorityRoundRobin requires a compare function to select next item based on priority.

JS

const cpusTable = new SequentialRoundRobin([1, 2, 3]);

const rockPaperScissors = new RandomRoundRobin(['Rock', 'Paper', 'Scissors']);

const availableServers = new PriorityRoundRobin(
  (a, b) => a.load - b.load, // select next available server with lowest load
  [{ hostname: 's1.test.com', load: 40 }, { hostname: 's2.test.com', load: 30 }]
);

TS

const cpusTable = new SequentialRoundRobin<number>([1, 2, 3]);

const rockPaperScissors = new RandomRoundRobin<string>(['Rock', 'Paper', 'Scissors']);

interface IServer {
  hostname: string;
  load: number;
}
const availableServers = new PriorityRoundRobin<IServer>(
  (a: IServer, b: IServer) => a.load - b.load, // select next available server with lowest load
  [{ hostname: 's1.test.com', load: 40 }, { hostname: 's2.test.com', load: 30 }]
);

add

adds a new item to the table.

cpusTable.add(4); // { key: 3, value: 4 }
cpusTable.add(5); // { key: 4, value: 5 }

availableServers.add({ hostname: 's3.test.com', load: 15 }); // { key: 2, value: { hostname: 's3.test.com', load: 15 } }
availableServers.add({ hostname: 's4.test.com', load: 60 }); // { key: 3, value: { hostname: 's4.test.com', load: 60 } }

next

selects and returns the next item in the round.

// first round
cpusTable.next(); // { key: 0, value: 1 }
cpusTable.next(); // { key: 1, value: 2 }
cpusTable.next(); // { key: 2, value: 3 }
cpusTable.next(); // { key: 3, value: 4 }
cpusTable.next(); // { key: 4, value: 5 }
// second round ...
cpusTable.next(); // { key: 0, value: 1 }

// first round
rockPaperScissors.next(); // { key: 1, value: 'Paper' }
rockPaperScissors.next(); // { key: 0, value: 'Rock' }
rockPaperScissors.next(); // { key: 2, value: 'Scissors' }
// second round ...
rockPaperScissors.next(); // { key: 0, value: 'Rock' }

availableServers.next(); // { key: 2, value: { hostname: 's3.test.com', load: 15 } }
availableServers.next(); // { key: 1, value: { hostname: 's2.test.com', load: 30 } }
availableServers.next(); // { key: 0, value: { hostname: 's1.test.com', load: 40 } }
availableServers.next(); // { key: 3, value: { hostname: 's4.test.com', load: 60 } }
// second round ...
availableServers.next(); // { key: 2, value: { hostname: 's3.test.com', load: 15 } }

count

returns the number of items in the table.

cpusTable.count(); // 5
rockPaperScissors.count(); // 3
availableServers.count(); // 4

deleteByKey

deletes an item from the table by its key.

cpusTable.deleteByKey(1); // 2 is deleted
cpusTable.count(); // 4

availableServers.deleteByKey(2); // true / { hostname: 's3.test.com', load: 15 } is deleted
availableServers.count(); // 3

deleteByValue

accepts a callback to delete items that match a criteria from the table and returns the count of deleted.

availableServers.deleteByValue((s) => s.load > 30); // 2
availableServers.next(); // { key: 1, value: { hostname: 's2.test.com', load: 30 } }
availableServers.next(); // { key: 1, value: { hostname: 's2.test.com', load: 30 } }

reset

resets the round selection from the start.

cpusTable.next(); // { key: 1, value: 2 }
cpusTable.next(); // { key: 2, value: 3 }
cpusTable.reset();
cpusTable.next(); // { key: 0, value: 1 }
cpusTable.next(); // { key: 1, value: 2 }

availableServers.next(); // { key: 1, value: { hostname: 's2.test.com', load: 30 } }
availableServers.add({ hostname: 's99.test.com', load: 10 });
availableServers.next(); // { key: 4, value: { hostname: 's99.test.com', load: 10 } }
availableServers.reset();
availableServers.next(); // { key: 4, value: { hostname: 's99.test.com', load: 10 } }

clear

clears all values in the table.

cpusTable.clear();
cpusTable.count(); // 0
cpusTable.next(); // null

rockPaperScissors.clear();
rockPaperScissors.count(); // 0
rockPaperScissors.next(); // null

availableServers.clear();
availableServers.count(); // 0
availableServers.next(); // null

Build

grunt build

License

The MIT License. Full License is here