467 lines
316 KiB
HTML
467 lines
316 KiB
HTML
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8" />
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<meta name="generator" content="pandoc" />
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<meta http-equiv="X-UA-Compatible" content="IE=EDGE" />
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<meta name="viewport" content="width=device-width, initial-scale=1" />
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<title>Advanced future and promises usage</title>
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<script>// Pandoc 2.9 adds attributes on both header and div. We remove the former (to
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// be compatible with the behavior of Pandoc < 2.8).
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document.addEventListener('DOMContentLoaded', function(e) {
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var hs = document.querySelectorAll("div.section[class*='level'] > :first-child");
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var i, h, a;
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for (i = 0; i < hs.length; i++) {
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h = hs[i];
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if (!/^h[1-6]$/i.test(h.tagName)) continue; // it should be a header h1-h6
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a = h.attributes;
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while (a.length > 0) h.removeAttribute(a[0].name);
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}
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});
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</script>
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<style type="text/css">.vembedr {
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margin-bottom: 10px;
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}
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.vembedr-rounded {
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display: inline-block;
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border-radius: 15px;
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overflow: hidden;
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}
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.vembedr-rounded iframe {
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display: block;
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border: none;
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}
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</style>
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<style type="text/css">
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code{white-space: pre-wrap;}
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span.smallcaps{font-variant: small-caps;}
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span.underline{text-decoration: underline;}
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div.column{display: inline-block; vertical-align: top; width: 50%;}
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div.hanging-indent{margin-left: 1.5em; text-indent: -1.5em;}
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ul.task-list{list-style: none;}
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</style>
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<style type="text/css">
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code {
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white-space: pre;
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}
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.sourceCode {
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overflow: visible;
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}
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</style>
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<style type="text/css" data-origin="pandoc">
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pre > code.sourceCode { white-space: pre; position: relative; }
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pre > code.sourceCode > span { display: inline-block; line-height: 1.25; }
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pre > code.sourceCode > span:empty { height: 1.2em; }
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.sourceCode { overflow: visible; }
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code.sourceCode > span { color: inherit; text-decoration: inherit; }
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div.sourceCode { margin: 1em 0; }
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pre.sourceCode { margin: 0; }
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@media screen {
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div.sourceCode { overflow: auto; }
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}
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@media print {
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pre > code.sourceCode { white-space: pre-wrap; }
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pre > code.sourceCode > span { text-indent: -5em; padding-left: 5em; }
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}
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pre.numberSource code
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{ counter-reset: source-line 0; }
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pre.numberSource code > span
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{ position: relative; left: -4em; counter-increment: source-line; }
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pre.numberSource code > span > a:first-child::before
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{ content: counter(source-line);
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position: relative; left: -1em; text-align: right; vertical-align: baseline;
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border: none; display: inline-block;
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-webkit-touch-callout: none; -webkit-user-select: none;
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-khtml-user-select: none; -moz-user-select: none;
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-ms-user-select: none; user-select: none;
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padding: 0 4px; width: 4em;
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color: #aaaaaa;
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}
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pre.numberSource { margin-left: 3em; border-left: 1px solid #aaaaaa; padding-left: 4px; }
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div.sourceCode
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{ }
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@media screen {
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pre > code.sourceCode > span > a:first-child::before { text-decoration: underline; }
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}
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code span.al { color: #ff0000; font-weight: bold; }
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code span.an { color: #60a0b0; font-weight: bold; font-style: italic; }
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code span.at { color: #7d9029; }
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code span.bn { color: #40a070; }
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code span.bu { color: #008000; }
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code span.cf { color: #007020; font-weight: bold; }
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code span.ch { color: #4070a0; }
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code span.cn { color: #880000; }
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code span.co { color: #60a0b0; font-style: italic; }
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code span.cv { color: #60a0b0; font-weight: bold; font-style: italic; }
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code span.do { color: #ba2121; font-style: italic; }
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code span.dt { color: #902000; }
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code span.dv { color: #40a070; }
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code span.er { color: #ff0000; font-weight: bold; }
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code span.ex { }
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code span.fl { color: #40a070; }
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code span.fu { color: #06287e; }
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code span.im { color: #008000; font-weight: bold; }
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code span.in { color: #60a0b0; font-weight: bold; font-style: italic; }
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code span.kw { color: #007020; font-weight: bold; }
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code span.op { color: #666666; }
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code span.ot { color: #007020; }
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code span.pp { color: #bc7a00; }
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code span.sc { color: #4070a0; }
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code span.ss { color: #bb6688; }
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code span.st { color: #4070a0; }
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code span.va { color: #19177c; }
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code span.vs { color: #4070a0; }
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code span.wa { color: #60a0b0; font-weight: bold; font-style: italic; }
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</style>
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<script>
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// apply pandoc div.sourceCode style to pre.sourceCode instead
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(function() {
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var sheets = document.styleSheets;
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for (var i = 0; i < sheets.length; i++) {
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if (sheets[i].ownerNode.dataset["origin"] !== "pandoc") continue;
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try { var rules = sheets[i].cssRules; } catch (e) { continue; }
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var j = 0;
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while (j < rules.length) {
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var rule = rules[j];
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// check if there is a div.sourceCode rule
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if (rule.type !== rule.STYLE_RULE || rule.selectorText !== "div.sourceCode") {
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j++;
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continue;
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}
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var style = rule.style.cssText;
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// check if color or background-color is set
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if (rule.style.color === '' && rule.style.backgroundColor === '') {
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j++;
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continue;
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}
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// replace div.sourceCode by a pre.sourceCode rule
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sheets[i].deleteRule(j);
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sheets[i].insertRule('pre.sourceCode{' + style + '}', j);
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}
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}
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})();
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</script>
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<style type="text/css">body {
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background-color: #fff;
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margin: 1em auto;
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max-width: 700px;
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overflow: visible;
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padding-left: 2em;
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padding-right: 2em;
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font-family: "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;
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font-size: 14px;
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line-height: 1.35;
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}
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#TOC {
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clear: both;
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margin: 0 0 10px 10px;
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padding: 4px;
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width: 400px;
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border: 1px solid #CCCCCC;
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border-radius: 5px;
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background-color: #f6f6f6;
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font-size: 13px;
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line-height: 1.3;
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}
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#TOC .toctitle {
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font-weight: bold;
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font-size: 15px;
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margin-left: 5px;
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}
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#TOC ul {
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padding-left: 40px;
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margin-left: -1.5em;
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margin-top: 5px;
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margin-bottom: 5px;
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}
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#TOC ul ul {
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margin-left: -2em;
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}
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#TOC li {
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line-height: 16px;
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}
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table {
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margin: 1em auto;
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border-width: 1px;
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border-color: #DDDDDD;
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border-style: outset;
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border-collapse: collapse;
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}
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table th {
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border-width: 2px;
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padding: 5px;
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border-style: inset;
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}
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table td {
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border-width: 1px;
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border-style: inset;
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line-height: 18px;
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padding: 5px 5px;
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}
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table, table th, table td {
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border-left-style: none;
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border-right-style: none;
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}
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table thead, table tr.even {
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background-color: #f7f7f7;
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}
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p {
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margin: 0.5em 0;
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}
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blockquote {
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background-color: #f6f6f6;
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padding: 0.25em 0.75em;
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}
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hr {
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border-style: solid;
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border: none;
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border-top: 1px solid #777;
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margin: 28px 0;
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}
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dl {
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margin-left: 0;
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}
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dl dd {
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margin-bottom: 13px;
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margin-left: 13px;
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}
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dl dt {
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font-weight: bold;
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}
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ul {
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margin-top: 0;
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}
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ul li {
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list-style: circle outside;
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}
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ul ul {
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margin-bottom: 0;
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}
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pre, code {
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background-color: #f7f7f7;
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border-radius: 3px;
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color: #333;
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white-space: pre-wrap;
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}
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pre {
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border-radius: 3px;
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margin: 5px 0px 10px 0px;
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padding: 10px;
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}
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pre:not([class]) {
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background-color: #f7f7f7;
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}
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code {
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font-family: Consolas, Monaco, 'Courier New', monospace;
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font-size: 85%;
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}
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p > code, li > code {
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padding: 2px 0px;
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}
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div.figure {
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text-align: center;
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}
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img {
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background-color: #FFFFFF;
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padding: 2px;
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border: 1px solid #DDDDDD;
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border-radius: 3px;
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border: 1px solid #CCCCCC;
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margin: 0 5px;
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}
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h1 {
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margin-top: 0;
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font-size: 35px;
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line-height: 40px;
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}
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h2 {
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border-bottom: 4px solid #f7f7f7;
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padding-top: 10px;
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padding-bottom: 2px;
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font-size: 145%;
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}
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h3 {
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border-bottom: 2px solid #f7f7f7;
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padding-top: 10px;
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font-size: 120%;
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}
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h4 {
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border-bottom: 1px solid #f7f7f7;
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margin-left: 8px;
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font-size: 105%;
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}
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h5, h6 {
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border-bottom: 1px solid #ccc;
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font-size: 105%;
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}
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a {
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color: #0033dd;
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text-decoration: none;
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}
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a:hover {
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color: #6666ff; }
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a:visited {
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color: #800080; }
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a:visited:hover {
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color: #BB00BB; }
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a[href^="http:"] {
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text-decoration: underline; }
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a[href^="https:"] {
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text-decoration: underline; }
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code > span.kw { color: #555; font-weight: bold; }
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code > span.dt { color: #902000; }
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code > span.dv { color: #40a070; }
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code > span.bn { color: #d14; }
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code > span.fl { color: #d14; }
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code > span.ch { color: #d14; }
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code > span.st { color: #d14; }
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code > span.co { color: #888888; font-style: italic; }
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code > span.ot { color: #007020; }
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code > span.al { color: #ff0000; font-weight: bold; }
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code > span.fu { color: #900; font-weight: bold; }
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code > span.er { color: #a61717; background-color: #e3d2d2; }
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</style>
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</head>
|
|||
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|
|||
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<body>
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|
|||
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|
|||
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|
|||
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<h1 class="title toc-ignore">Advanced future and promises usage</h1>
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|||
|
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|
|||
|
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|
|||
|
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|
|||
|
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<p>This article discusses the benefits of using
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|
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<code>promises::future_promise()</code> over a combination of
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|||
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<code>future::future()</code> + <code>promises::promise()</code> to
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|||
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better take advantage of computing resources available to your main R
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|
|
session. To demonstrate these benefits, we’ll walk-through a use-case
|
|||
|
|
with the <code>plumber</code> package. (<a href="https://www.rplumber.io/">See here</a> to learn more about
|
|||
|
|
<code>plumber</code> and <a href="promises_04_futures.html">the previous
|
|||
|
|
article</a> to learn more about <code>future</code>.)</p>
|
|||
|
|
<div id="the-problem-with-futurepromise" class="section level2">
|
|||
|
|
<h2>The problem with <code>future()</code>+<code>promise()</code></h2>
|
|||
|
|
<p>In an ideal situation, the number of available <code>future</code>
|
|||
|
|
<em>workers</em> (<code>future::nbrOfFreeWorkers()</code>) is always
|
|||
|
|
<strong>more than</strong> the number of <code>future::future()</code>
|
|||
|
|
<em>jobs</em>. However, if a <code>future</code> job is attempted when
|
|||
|
|
the number of free workers is <code>0</code>, then <code>future</code>
|
|||
|
|
will block the current R session until one becomes available.</p>
|
|||
|
|
<p>For a concrete example, let’s imagine a scenario, where seven
|
|||
|
|
<code>plumber</code> requests are received at the same time with only
|
|||
|
|
two <code>future</code> workers available. Also, let’s assume the
|
|||
|
|
<code>plumber</code> route(s) serving the first 6 requests use
|
|||
|
|
<code>future::future()</code> and take ~10s to compute
|
|||
|
|
<code>slow_calc()</code>:</p>
|
|||
|
|
<div class="sourceCode" id="cb1"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="co">#* @get /slow/<k></span></span>
|
|||
|
|
<span id="cb1-2"><a href="#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="cf">function</span>() {</span>
|
|||
|
|
<span id="cb1-3"><a href="#cb1-3" aria-hidden="true" tabindex="-1"></a> future<span class="sc">::</span><span class="fu">future</span>({</span>
|
|||
|
|
<span id="cb1-4"><a href="#cb1-4" aria-hidden="true" tabindex="-1"></a> <span class="fu">slow_calc</span>()</span>
|
|||
|
|
<span id="cb1-5"><a href="#cb1-5" aria-hidden="true" tabindex="-1"></a> })</span>
|
|||
|
|
<span id="cb1-6"><a href="#cb1-6" aria-hidden="true" tabindex="-1"></a>}</span></code></pre></div>
|
|||
|
|
<p>Let’s also assume the <code>plumber</code> route serving the last
|
|||
|
|
request does not use any form of <code>future</code> or
|
|||
|
|
<code>promises</code> and takes almost no time to compute.</p>
|
|||
|
|
<div class="sourceCode" id="cb2"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="co">#* @get /fast/<k></span></span>
|
|||
|
|
<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="cf">function</span>() {</span>
|
|||
|
|
<span id="cb2-3"><a href="#cb2-3" aria-hidden="true" tabindex="-1"></a> <span class="fu">fast_calc</span>()</span>
|
|||
|
|
<span id="cb2-4"><a href="#cb2-4" aria-hidden="true" tabindex="-1"></a>}</span></code></pre></div>
|
|||
|
|
<p>The figure below depicts the overall timeline of execution of these 7
|
|||
|
|
requests under the conditions we’ve outlined above. Note that the y-axis
|
|||
|
|
is ordered from first request coming in (<code>/slow/1</code>) to the
|
|||
|
|
last request (<code>/fast/7</code>).</p>
|
|||
|
|
<p><img src="data:image/png;base64,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
|
|||
|
|
<p>Note how R has to wait 20s before processing the 7th request (shown
|
|||
|
|
in green). This is a big improvement over not using
|
|||
|
|
<code>future</code>+<code>promises</code> at all (in that case, R would
|
|||
|
|
have to wait 60s before processing). However, since there are only two
|
|||
|
|
<code>future</code> workers available R still has to wait longer than
|
|||
|
|
necessary to process that last request because the main R session must
|
|||
|
|
wait for a <code>future</code> worker to become available. The video
|
|||
|
|
below animates this behavior:</p>
|
|||
|
|
<div class="vembedr" align="center">
|
|||
|
|
<div>
|
|||
|
|
<iframe class="vimeo-embed" src="https://player.vimeo.com/video/505287449" width="533" height="300" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen data-external="1"></iframe>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div id="the-solution-future_promise" class="section level2">
|
|||
|
|
<h2>The solution: <code>future_promise()</code></h2>
|
|||
|
|
<p>The advantage of using <code>future_promise()</code> over
|
|||
|
|
<code>future::future()</code> is that even if there aren’t
|
|||
|
|
<code>future</code> workers available, the <code>future</code> is
|
|||
|
|
scheduled to be done when workers become available via
|
|||
|
|
<code>promises</code>. In other words, <code>future_promise()</code>
|
|||
|
|
ensures the main R thread isn’t blocked when a <code>future</code> job
|
|||
|
|
is requested and can’t immediately perform the work (i.e., the number of
|
|||
|
|
jobs exceeds the number of workers).</p>
|
|||
|
|
<p>Continuing with the example above, we can swap out the calls to
|
|||
|
|
<code>future::future()</code> with <code>future_promise()</code>.</p>
|
|||
|
|
<div class="sourceCode" id="cb3"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="co">#* @get /slow/<k></span></span>
|
|||
|
|
<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a><span class="cf">function</span>() {</span>
|
|||
|
|
<span id="cb3-3"><a href="#cb3-3" aria-hidden="true" tabindex="-1"></a> promises<span class="sc">::</span><span class="fu">future_promise</span>({</span>
|
|||
|
|
<span id="cb3-4"><a href="#cb3-4" aria-hidden="true" tabindex="-1"></a> <span class="fu">slow_calc</span>()</span>
|
|||
|
|
<span id="cb3-5"><a href="#cb3-5" aria-hidden="true" tabindex="-1"></a> })</span>
|
|||
|
|
<span id="cb3-6"><a href="#cb3-6" aria-hidden="true" tabindex="-1"></a>}</span></code></pre></div>
|
|||
|
|
<p>With this change to <code>future_promise()</code>, note how the
|
|||
|
|
<code>/fast/7</code> route now does not have to wait on
|
|||
|
|
<code>future</code> work to finish processing. Therefore,
|
|||
|
|
<code>plumber</code> can complete the last requests almost
|
|||
|
|
immediately:</p>
|
|||
|
|
<p><img src="data:image/png;base64,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
|
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<p>The vertical gray bars in the figure above represent timepoints where
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|
|
the main R session is actually busy. Outside of these gray areas, the R
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session is free to do other things, for example, executing other
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<code>promises</code> or, more generally, non-<code>future</code> work.
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The video below animates this behavior:</p>
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<div class="vembedr" align="center">
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<div>
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<iframe class="vimeo-embed" src="https://player.vimeo.com/video/505286442" width="533" height="300" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen data-external="1"></iframe>
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</div>
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</div>
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<div style="font-size: 20px; margin-top: 40px; text-align: right;">
|
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|
|
<p>Next: <a href="promises_06_shiny.html">Using <code>promises</code>
|
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|
|
with Shiny</a></p>
|
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</div>
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</div>
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script.type = "text/javascript";
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script.src = "https://mathjax.rstudio.com/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML";
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document.getElementsByTagName("head")[0].appendChild(script);
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