Created
December 16, 2022 01:24
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import { createHash, randomBytes } from "crypto"; | |
interface INode<T = any> { | |
id: number; | |
data: Map<string, T>; | |
hash: string; | |
} | |
interface IHashRing { | |
nodes: INode<any>[]; | |
addNode(node: INode): void; | |
removeNode(node: INode): INode; | |
putObject(doc: Document): void; | |
getObject(collectionName: string, id: number): Document | undefined; | |
} | |
interface Document<T = any> { | |
keyName: string; | |
collectionName: string; | |
data: T; | |
} | |
function createNodeHash(): string { | |
return randomBytes(4).toString("hex"); | |
} | |
function createObjectHash(key: string): string { | |
return createHash("shake256", { outputLength: 4 }).update(key).digest("hex"); | |
} | |
function isHashGreaterThan(hash1: string, hash2: string): boolean { | |
return parseInt(hash1, 16) > parseInt(hash2, 16); | |
} | |
class ServerNode<T> implements INode<T> { | |
public hash: string; | |
constructor(public id: number, public data = new Map<string, T>()) { | |
this.hash = createNodeHash(); | |
} | |
} | |
class HashRing implements IHashRing { | |
constructor(public nodes: INode[] = []) {} | |
public addNode(node: INode): void { | |
let placedIndex = -1; | |
let i = -1; | |
while (++i < this.nodes.length) { | |
const currentNode = this.nodes[i]; | |
const shouldPlaceNode = !isHashGreaterThan(node.hash, currentNode.hash); | |
if (shouldPlaceNode) { | |
this.nodes.splice(i, 0, node); | |
placedIndex = i; | |
break; | |
} | |
} | |
if (placedIndex === -1) { | |
this.nodes.push(node); | |
const nodeIndexToBeRehashed = 0; | |
this._rehash(this.nodes[nodeIndexToBeRehashed]); | |
} else { | |
this._rehash(this.nodes[placedIndex + 1]); | |
} | |
} | |
public removeNode(node: INode): INode { | |
this.nodes.splice(this.nodes.indexOf(node), 1); | |
this._rehash(node); | |
return node; | |
} | |
public putObject(doc: Document): void { | |
const hash = createObjectHash( | |
`${doc.collectionName}:${doc.data[doc.keyName]}`, | |
); | |
const nodeToPlaceDoc = this._findNode(hash); | |
nodeToPlaceDoc.data.set(hash, doc); | |
} | |
public getObject(collectionName: string, id: number): Document | undefined { | |
const hash = createObjectHash(`${collectionName}:${id}`); | |
const node = this._findNode(hash); | |
const object = node.data.get(hash); | |
return object ? { ...object, nodeHash: node.hash } : undefined; | |
} | |
protected _rehash(nodeToRehash: INode) { | |
for (const [hash, objectValue] of nodeToRehash.data.entries()) { | |
const newNode = this._findNode(hash); | |
const shouldPlaceToDifferentNode = newNode !== nodeToRehash; | |
if (shouldPlaceToDifferentNode) { | |
newNode.data.set(hash, objectValue); | |
nodeToRehash.data.delete(hash); | |
} | |
} | |
} | |
protected _findNode(docHash: string): INode { | |
let start = 0; | |
let end = this.nodes.length; | |
let cursor = start + Math.floor((end - start) / 2); | |
while (start < end && this.nodes[cursor]) { | |
if (isHashGreaterThan(docHash, this.nodes[cursor].hash)) { | |
start = cursor + 1; | |
} else { | |
end = cursor; | |
} | |
cursor = start + Math.floor((end - start) / 2); | |
} | |
return this.nodes[cursor < this.nodes.length ? cursor : 0]; | |
} | |
} | |
const hashRing = new HashRing(); | |
const node1 = new ServerNode<any>(1); | |
const node2 = new ServerNode<any>(2); | |
hashRing.addNode(node1); | |
hashRing.addNode(node2); | |
// insert data | |
for (let i = 0; i < 1000; i++) { | |
hashRing.putObject({ | |
collectionName: "users", | |
keyName: "user_id", | |
data: { | |
user_id: i + 1, | |
name: String.fromCharCode(65 + Math.floor(Math.random() * 26)), | |
age: Math.floor(Math.random() * 100 + 18), | |
salary: "£100000", | |
}, | |
}); | |
} | |
console.log(hashRing.getObject("users", 300)); | |
console.log(hashRing.getObject("users", 500)); | |
console.log("\nAdding 2 new server nodes \n"); | |
const node3 = new ServerNode<any>(3); | |
const node4 = new ServerNode<any>(4); | |
hashRing.addNode(node3); | |
hashRing.addNode(node4); | |
console.log(hashRing.getObject("users", 300)); | |
console.log(hashRing.getObject("users", 500)); | |
console.log("\nRemoving Added server nodes \n"); | |
const removedNode3 = hashRing.removeNode(node3); | |
const removedNode4 = hashRing.removeNode(node4); | |
console.log(hashRing.getObject("users", 300)); | |
console.log(hashRing.getObject("users", 500)); | |
console.log("\nRe-adding the removed server nodes \n"); | |
hashRing.addNode(removedNode3); | |
hashRing.addNode(removedNode4); | |
console.log(hashRing.getObject("users", 300)); | |
console.log(hashRing.getObject("users", 500)); | |
console.log("\nAdding 10 new server nodes \n"); | |
hashRing.addNode(new ServerNode<any>(5)); | |
hashRing.addNode(new ServerNode<any>(6)); | |
hashRing.addNode(new ServerNode<any>(7)); | |
hashRing.addNode(new ServerNode<any>(8)); | |
hashRing.addNode(new ServerNode<any>(9)); | |
hashRing.addNode(new ServerNode<any>(10)); | |
hashRing.addNode(new ServerNode<any>(11)); | |
hashRing.addNode(new ServerNode<any>(12)); | |
hashRing.addNode(new ServerNode<any>(13)); | |
hashRing.addNode(new ServerNode<any>(14)); | |
console.log(hashRing.getObject("users", 300)); | |
console.log(hashRing.getObject("users", 500)); | |
console.log( | |
"Server node hashring hash range", | |
hashRing.nodes.map((item) => item.hash), | |
); |
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