{"id":23119,"date":"2018-11-02T12:15:35","date_gmt":"2018-11-02T10:15:35","guid":{"rendered":"https:\/\/www.webcodegeeks.com\/?p=23119"},"modified":"2018-11-02T11:05:42","modified_gmt":"2018-11-02T09:05:42","slug":"beware-performance-cost-async_hooks-node","status":"publish","type":"post","link":"https:\/\/www.webcodegeeks.com\/javascript\/node-js\/beware-performance-cost-async_hooks-node\/","title":{"rendered":"Beware the performance cost of async_hooks (Node 8)"},"content":{"rendered":"<p>I was excited about <a href=\"https:\/\/nodejs.org\/api\/async_hooks.html\">async_hooks<\/a> having finally landed in Node.js 8, as it would enable me to share important troubleshooting information with all code involved in handling a particular request. However it turned out to have terrible impact of our CPU usage (YMMV):<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n&nbsp;<br \/>\n<a href=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu_load_prod_20181023.jpg\"><img decoding=\"async\" class=\"aligncenter wp-image-23125 size-full\" src=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu_load_prod_20181023.jpg\" alt=\"async_hooks\" width=\"524\" height=\"221\" srcset=\"https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu_load_prod_20181023.jpg 524w, https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu_load_prod_20181023-300x127.jpg 300w\" sizes=\"(max-width: 524px) 100vw, 524px\" \/><\/a><\/p>\n<p>This was quite extreme and is likely related to the way how our application works and uses Promises. Do your own testing to measure the actual impact in your app.<\/p>\n<p>However I am not the only one who has seen some performance hit from async_hooks \u2013 see\u00a0<a href=\"https:\/\/github.com\/bmeurer\/async-hooks-performance-impact\">https:\/\/github.com\/bmeurer\/async-hooks-performance-impact<\/a>, in particular:<\/p>\n<p>Here the results of running the Promise micro benchmarks with and without\u00a0<code>async_hooks<\/code>\u00a0enabled:<\/p>\n<table border=\"1\">\n<thead>\n<tr>\n<th>Benchmark<\/th>\n<th>Node 8.9.4<\/th>\n<th>Node 9.4.0<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Bluebird-doxbee (regular)<\/td>\n<td>226 ms<\/td>\n<td>189 ms<\/td>\n<\/tr>\n<tr>\n<td>Bluebird-doxbee (init hook)<\/td>\n<td>383 ms<\/td>\n<td>341 ms<\/td>\n<\/tr>\n<tr>\n<td>Bluebird-doxbee (all hooks)<\/td>\n<td>440 ms<\/td>\n<td>411 ms<\/td>\n<\/tr>\n<tr>\n<td>Bluebird-parallel (regular)<\/td>\n<td>924 ms<\/td>\n<td>696 ms<\/td>\n<\/tr>\n<tr>\n<td>Bluebird-parallel (init hook)<\/td>\n<td>1380 ms<\/td>\n<td>1050 ms<\/td>\n<\/tr>\n<tr>\n<td>Bluebird-parallel (all hooks)<\/td>\n<td>1488 ms<\/td>\n<td>1220 ms<\/td>\n<\/tr>\n<tr>\n<td>Wikipedia (regular)<\/td>\n<td>993 ms<\/td>\n<td>804 ms<\/td>\n<\/tr>\n<tr>\n<td>Wikipedia (init hook)<\/td>\n<td>2025 ms<\/td>\n<td>1893 ms<\/td>\n<\/tr>\n<tr>\n<td>Wikipedia (all hooks)<\/td>\n<td>2109 ms<\/td>\n<td>2124 ms<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>To confirm the impact of async_hook on our app, I have performed 3 performance tests:<\/p>\n<h2>CPU usage without async_hooks (Node 8)<\/h2>\n<p>It is difficult to see but the mean CPU usage is perhaps around 60% here.<\/p>\n<p><a href=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-no-async-hooks.png\"><img decoding=\"async\" class=\"aligncenter wp-image-23126 size-full\" src=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-no-async-hooks.png\" alt=\"async_hooks\" width=\"500\" height=\"378\" srcset=\"https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-no-async-hooks.png 500w, https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-no-async-hooks-300x227.png 300w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/><\/a><\/p>\n<h2>CPU usage with \u201cno-op\u201d async_hooks (Node 8)<\/h2>\n<p>Here the CPU jumped to 100%.<\/p>\n<p><a href=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks.png\"><img decoding=\"async\" class=\"aligncenter wp-image-23127 size-full\" src=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks.png\" alt=\"async_hooks\" width=\"500\" height=\"378\" srcset=\"https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks.png 500w, https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks-300x227.png 300w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/><\/a><\/p>\n<h2>CPU usage with \u201cno-op\u201d async_hooks (Node 11)<\/h2>\n<p>The same as above, but using Node 11 for comparison. I recorded it for just a few minutes but the CPU usage is still around 100%:<\/p>\n<p><a href=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks-node11.png\"><img decoding=\"async\" class=\"aligncenter wp-image-23128 size-full\" src=\"http:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks-node11.png\" alt=\"async_hooks\" width=\"500\" height=\"378\" srcset=\"https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks-node11.png 500w, https:\/\/www.webcodegeeks.com\/wp-content\/uploads\/2018\/11\/cpu-usage-with-async-hooks-node11-300x227.png 300w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/><\/a><\/p>\n<h3>The code<\/h3>\n<p>This is the relevant code:<\/p>\n<pre class=\"brush:js\">  \r\n const asyncHooks = require('async_hooks'); \/\/ Node 8.9+\r\nconst querystring = require('querystring');\r\nconst crypto = require(\"crypto\");\r\n\r\nconst context = {};\r\n\r\nfunction createHooks() {\r\n    function init(asyncId, type, triggerId, resource) {\r\n        \/\/ if (context[triggerId]) {\r\n        \/\/     context[asyncId] = context[triggerId];\r\n        \/\/ }\r\n    }\r\n\r\n    function destroy(asyncId) {\r\n        \/\/ delete context[asyncId];\r\n    }\r\n\r\n    const asyncHook = asyncHooks.createHook({ init, destroy });\r\n\r\n    asyncHook.enable();\r\n}\r\n\r\ncreateHooks()<\/pre>\n<div class=\"attribution\">\n<table>\n<tbody>\n<tr>\n<td>Published on Web Code Geeks with permission by Jakub Holy, partner at our <a href=\"\/\/www.webcodegeeks.com\/join-us\/wcg\/\" target=\"_blank\" rel=\"noopener\">WCG program<\/a>. See the original article here: <a href=\"https:\/\/theholyjava.wordpress.com\/2018\/11\/01\/beware-the-performance-cost-of-async_hooks-node-8\/\" target=\"_blank\" rel=\"noopener\">Beware the performance cost of async_hooks (Node 8)<\/a><\/p>\n<p>Opinions expressed by Web Code Geeks contributors are their own.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>I was excited about async_hooks having finally landed in Node.js 8, as it would enable me to share important troubleshooting information with all code involved in handling a particular request. However it turned out to have terrible impact of our CPU usage (YMMV): &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; This was quite extreme &hellip;<\/p>\n","protected":false},"author":52,"featured_media":924,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"class_list":["post-23119","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-node-js"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Beware the performance cost of async_hooks (Node 8) - Web Code Geeks - 2026<\/title>\n<meta name=\"description\" content=\"Interested to learn about async_hooks? 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