pool-watch

A live chart renderer of the distribution of promises across a promise pool.

Current version: 1.0.1

Lead Maintainer: Halim Qarroum

Install

$ npm install --save pool-watch

Description

The pool-watch module has been written to monitor the distribution of promise executions within a promise pool instance, by displaying a live chart of the state of the promise pool executors.

This module is only compatible with a promise-pool, and will not work for other pool implementations.

Usage

To use pool-watch, simply require it into your application.

const watch = require('pool-watch');

The returned watch function takes as an input a reference to the promise pool, as well as an options object which will be forwarded to progress-string which is used to create the chart.

The options you can pass as a second argument to watch are the following :

• total - (integer) The maximum amount of promises you would like to monitor (mandatory).
• width - (integer, default: 42) The width of the progress bar in chars
• incomplete - (string, default: -) The char used to indicate the incomplete part of the progress bar
• complete - (string, default: =) The char used to indicate the completed part of the progress bar
• style - (function, optional) See options.style below for details

For more informations on the options object, see the progress-string module.

Return value

The returned value of a call to the watch function is a Node.js Stream, allowing you to .pipe() the live chart to any writable stream (e.g process.stdout, or a net.Socket for remote monitoring with netcat).

Example

// Creating the promise pool with `5` executors.
const pool = new Pool(5);
// The number of promises we'll insert.
const total = 1000;

// Configuring `watch` to display the live chart on `stdout`.
watch(pool, { total }).pipe(process.stdout);

// Scheduling promises in the pool.
for (let i = 0; i < total; ++i) {
  pool.schedule(() => new Promise((r) => setTimeout(r, 200)));
}

See also

• The Promise Pool module
• A promise pool watcher command-line application example
• The progress-string module