Copy file sloooooowly, so that we can test network related stuff

slow_copy.js

#!/usr/bin/env node

var fs = require('fs');
var util = require('util');

var DEFAULT_BPS = 10 * 1000; // 10 kb / sec

var source = process.argv[2];
if (!source) {
	return usage(1);
}

var dest = process.argv[3];
if (!dest) {
	return usage(1);
}

var PARAMS = {
	bps: Number(process.argv[4]) || DEFAULT_BPS
};
PARAMS.chunkSize = PARAMS.bps / 10;
PARAMS.highWaterMark = PARAMS.chunkSize * 6;
PARAMS.lowWaterMark = PARAMS.chunkSize * 3;

var STATS = {
	read: 0,
	written: 0
};

var buffer = new Buffer(0),
	finishedReading = false;

var rs = fs.createReadStream(source, {});
var ws = fs.createWriteStream(dest, {
	mode: 0664
});

rs.on('data', function (data) {
	STATS.read += data.length;
	buffer = Buffer.concat([buffer, data]);
	if (buffer.length > PARAMS.highWaterMark) {
		rs.pause();
	}
});

rs.on('end', function () {
	console.log('Done reading');
	finishedReading = true;
});

var flushInterval = setInterval(flush, 100);
var reportingInterval = setInterval(report, 1000);

function usage(exitCode) {
	console.log(util.format('Usage: %s %s <source> <dest> [bps]', process.argv[0], process.argv[1]));
	process.exit(exitCode >= 0 ? exitCode : 0);
}

function flush() {
	var chunk = buffer.slice(0, PARAMS.chunkSize);
	if (chunk.length > 0) {
		ws.write(chunk);
		STATS.written += chunk.length;
		buffer = buffer.slice(chunk.length);
		if (buffer.length < PARAMS.lowWaterMark) {
			rs.resume();
		}
	}
	else if (finishedReading) {
		ws.end();
		clearInterval(flushInterval);
		clearInterval(reportingInterval);
		console.log('Done writing');
	}
}

function report() {
	console.log(util.format('Read: %s | Written: %s | Buffered: %s', STATS.read, STATS.written, buffer.length));
}