kafka-streams/lib/KStorage.js

kafka-streams for Node.js

"use strict";

const Promise = require("bluebird");

class KStorage {

    /**
     * be aware that even though KStorage is built on Promises
     * its operations must always be ATOMIC (or ACID) because
     * the stream will access them parallel, therefore having
     * an async get + async set operation will always yield
     * in a large amount of missing get operations followed by
     * set operations
     */
    constructor(options) {
        this.options = options;
        this.state = {};
    }

    /* NOTE: there is no open() method, meaning the functions have to work lazily */

    set(key, value) {
        this.state[key] = value;
        return Promise.resolve(value);
    }

    setSmaller(key = "min", value) {

        if (!this.state[key]) {
            this.state[key] = value;
        }

        if (value < this.state[key]) {
            this.state[key] = value;
        }

        return Promise.resolve(this.state[key]);
    }

    setGreater(key = "max", value) {

        if (!this.state[key]) {
            this.state[key] = value;
        }

        if (value > this.state[key]) {
            this.state[key] = value;
        }

        return Promise.resolve(this.state[key]);
    }

    increment(key, by = 1) {
        if (!this.state[key]) {
            this.state[key] = by;
        } else {
            this.state[key] += by;
        }
        return Promise.resolve(this.state[key]);
    }

    sum(key, value) {
        return this.increment(key, value);
    }

    get(key) {
        return Promise.resolve(this.state[key]);
    }

    getState() {
        return Promise.resolve(this.state);
    }

    setState(newState) {
        this.state = newState;
        return Promise.resolve(true);
    }

    getMin(key = "min") {
        return Promise.resolve(this.state[key]);
    }

    getMax(key = "max") {
        return Promise.resolve(this.state[key]);
    }

    close() {
        return Promise.resolve(true);
    }
}

module.exports = KStorage;