diff options
| author | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
|---|---|---|
| committer | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
| commit | fe3492a98de29942477b061cd02c92246f4bf85a (patch) | |
| tree | 2255b796a657e6e4dfb72beec1141258d17f1220 /articles/erlang-scalability | |
| download | ninenines.eu-fe3492a98de29942477b061cd02c92246f4bf85a.tar.gz ninenines.eu-fe3492a98de29942477b061cd02c92246f4bf85a.tar.bz2 ninenines.eu-fe3492a98de29942477b061cd02c92246f4bf85a.zip | |
Initial commit, new website system
Diffstat (limited to 'articles/erlang-scalability')
| -rw-r--r-- | articles/erlang-scalability/index.html | 293 |
1 files changed, 293 insertions, 0 deletions
diff --git a/articles/erlang-scalability/index.html b/articles/erlang-scalability/index.html new file mode 100644 index 00000000..6acc3e87 --- /dev/null +++ b/articles/erlang-scalability/index.html @@ -0,0 +1,293 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Erlang Scalability</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li class="active"><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents"> +<div class="container"> +<div class="row"> +<div class="span9 maincol"> + +<article class="blog_item"> +<header> + <h1 class="lined-header"><span>Erlang Scalability</span></h1> + <p class="date"> + <span class="day">18</span> + <span class="month">Feb</span> + </p> +</header> + +<div class="paragraph"><p>I would like to share some experience and theories on
+Erlang scalability.</p></div>
+<div class="paragraph"><p>This will be in the form of a series of hints, which
+may or may not be accompanied with explanations as to why
+things are this way, or how they improve or reduce the scalability
+of a system. I will try to do my best to avoid giving falsehoods,
+even if that means a few things won’t be explained.</p></div>
+<div class="sect1">
+<h2 id="_nifs">NIFs</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>NIFs are considered harmful. I don’t know any single NIF-based
+library that I would recommend. That doesn’t mean they should
+all be avoided, just that if you’re going to want your system to
+scale, you probably shouldn’t use a NIF.</p></div>
+<div class="paragraph"><p>A common case for using NIFs is JSON processing. The problem
+is that JSON is a highly inefficient data structure (similar
+in inefficiency to XML, although perhaps not as bad). If you can
+avoid using JSON, you probably should. MessagePack can replace
+it in many situations.</p></div>
+<div class="paragraph"><p>Long-running NIFs will take over a scheduler and prevent Erlang
+from efficiently handling many processes.</p></div>
+<div class="paragraph"><p>Short-running NIFs will still confuse the scheduler if they
+take more than a few microseconds to run.</p></div>
+<div class="paragraph"><p>Threaded NIFs, or the use of the <code>enif_consume_timeslice</code>
+might help allievate this problem, but they’re not a silver bullet.</p></div>
+<div class="paragraph"><p>And as you already know, a crashing NIF will take down your VM,
+destroying any claims you may have at being scalable.</p></div>
+<div class="paragraph"><p>Never use a NIF because "C is fast". This is only true in
+single-threaded programs.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_bifs">BIFs</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>BIFs can also be harmful. While they are generally better than
+NIFs, they are not perfect and some of them might have harmful
+effects on the scheduler.</p></div>
+<div class="paragraph"><p>A great example of this is the <code>erlang:decode_packet/3</code>
+BIF, when used for HTTP request or response decoding. Avoiding
+its use in <em>Cowboy</em> allowed us to see a big increase in
+the number of requests production systems were able to handle,
+up to two times the original amount. Incidentally this is something
+that is impossible to detect using synthetic benchmarks.</p></div>
+<div class="paragraph"><p>BIFs that return immediately are perfectly fine though.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_binary_strings">Binary strings</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Binary strings use less memory, which means you spend less time
+allocating memory compared to list-based strings. They are also
+more natural for strings manipulation because they are optimized
+for appending (as opposed to prepending for lists).</p></div>
+<div class="paragraph"><p>If you can process a binary string using a single match context,
+then the code will run incredibly fast. The effects will be much
+increased if the code was compiled using HiPE, even if your Erlang
+system isn’t compiled natively.</p></div>
+<div class="paragraph"><p>Avoid using <code>binary:split</code> or <code>binary:replace</code>
+if you can avoid it. They have a certain overhead due to supporting
+many options that you probably don’t need for most operations.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_buffering_and_streaming">Buffering and streaming</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Use binaries. They are great for appending, and it’s a direct copy
+from what you receive from a stream (usually a socket or a file).</p></div>
+<div class="paragraph"><p>Be careful to not indefinitely receive data, as you might end up
+having a single binary taking up huge amounts of memory.</p></div>
+<div class="paragraph"><p>If you stream from a socket and know how much data you expect,
+then fetch that data in a single <code>recv</code> call.</p></div>
+<div class="paragraph"><p>Similarly, if you can use a single <code>send</code> call, then
+you should do so, to avoid going back and forth unnecessarily between
+your Erlang process and the Erlang port for your socket.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_list_and_binary_comprehensions">List and binary comprehensions</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Prefer list comprehensions over <code>lists:map/2</code>. The
+compiler will be able to optimize your code greatly, for example
+not creating the result if you don’t need it. As time goes on,
+more optimizations will be added to the compiler and you will
+automatically benefit from them.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_gen_server_is_no_silver_bullet">gen_server is no silver bullet</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>It’s a bad idea to use <code>gen_server</code> for everything.
+For two reasons.</p></div>
+<div class="paragraph"><p>There is an overhead everytime the <code>gen_server</code> receives
+a call, a cast or a simple message. It can be a problem if your
+<code>gen_server</code> is in a critical code path where speed
+is all that matters. Do not hesitate to create other kinds of
+processes where it makes sense. And depending on the kind of process,
+you might want to consider making them special processes, which
+would essentially behave the same as a <code>gen_server</code>.</p></div>
+<div class="paragraph"><p>A common mistake is to have a unique <code>gen_server</code> to
+handle queries from many processes. This generally becomes the
+biggest bottleneck you’ll want to fix. You should try to avoid
+relying on a single process, using a pool if you can.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_supervisor_and_monitoring">Supervisor and monitoring</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>A <code>supervisor</code> is also a <code>gen_server</code>,
+so the previous points also apply to them.</p></div>
+<div class="paragraph"><p>Sometimes you’re in a situation where you have supervised
+processes but also want to monitor them in one or more other
+processes, effectively duplicating the work. The supervisor
+already knows when processes die, why not use this to our
+advantage?</p></div>
+<div class="paragraph"><p>You can create a custom supervisor process that will perform
+both the supervision and handle exit and other events, allowing
+to avoid the combination of supervising and monitoring which
+can prove harmful when many processes die at once, or when you
+have many short lived processes.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_ets_for_lolspeed_tm">ets for LOLSPEED(tm)</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>If you have data queried or modified by many processes, then
+<code>ets</code> public or protected tables will give you the
+performance boost you require. Do not forget to set the
+<code>read_concurrency</code> or <code>write_concurrency</code>
+options though.</p></div>
+<div class="paragraph"><p>You might also be thrilled to know that Erlang R16B will feature
+a big performance improvement for accessing <code>ets</code> tables
+concurrently.</p></div>
+</div>
+</div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="http://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="http://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="http://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="http://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="http://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="http://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="http://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="http://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="http://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="http://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="http://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></li> + +</ul> + +<h3>Feedback</h3> +<p>Feel free to <a href="mailto:[email protected]">email us</a> +if you found any mistake or need clarification on any of the +articles.</p> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + |