andresusandi-storage/ConsistentHashShard.js

storage utilities for distributed systems

const { name: packageName } = require('./package.json');

const PREFIX = "key-gen-";

class ConsistentHashShard {
    constructor(shardIndex, storageConstructor, counterConstructor) {
        this.shardIndex = shardIndex;
        this.name = PREFIX + shardIndex.toString();
        this.storageConstructor = storageConstructor;
        this.storage = null;
        this.counterConstructor = counterConstructor;
        this.counter = null;
    }

    async init() {
        this.storage = this.storageConstructor(this.shardIndex);
        await this.storage.init();
        this.counter = this.counterConstructor();
        const itemCount = (await this.storage.getAllItems()).length;
        await this.counter.set(this.name, itemCount);
        console.log(`${packageName}/${this.constructor.name}: Initialized instance of shard for ${this.shardIndex} with ${itemCount} items`);
    }

    async save(key, value) {
        await this.storage.save(key, value);
    }

    async get(key) {
        return(await this.storage.get(key));
    }

    async delete(key) {
        await this.storage.delete(key);
    }

    async getAllItems() {
        return (await this.storage.getAllItems());
    }

    async getCount() {
        const result = await this.counter.get(this.name);
        return (result.value);
    }

    async setCount(itemCount) {
        await this.counter.set(this.name, itemCount);
    }

    async modifyCount(byCount) {
        await this.counter.add(this.name, byCount);
    }
}

module.exports = ConsistentHashShard;