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diff --git a/_build/content/articles/dont-let-it-crash.asciidoc b/_build/content/articles/dont-let-it-crash.asciidoc new file mode 100644 index 00000000..f4f15c79 --- /dev/null +++ b/_build/content/articles/dont-let-it-crash.asciidoc @@ -0,0 +1,141 @@ ++++ +date = "2017-01-22T00:00:00+01:00" +title = "Don't let it crash" + ++++ + +We have a specific mindset when writing Erlang +programs. We focus on the normal execution of the +program and don't handle most of the errors that may +occur. We sometimes call this normal execution the +'happy path'. + +The general pattern behind writing only for the +'happy path', letting the VM catch errors (writing +them to a log for future consumption) and then +having a supervisor restart the processes that +failed from a clean state, has a name. We call it +'let it crash'; and it drives many of our design +decisions. + +It's a really great way to program and the results +are fantastic compared to most other programming +languages. And yet, 'let it crash' barely convinced +anyone that they should use Erlang. Why would that +be? + +You may already know that Cowboy is capable of +handling at least 2 million Websocket connections +on a single server. This is in large part thanks +to the capabilities of the VM. Still, 2 million +is good, much better than most other servers can +do. + +Cowboy is not just a Websocket server; it's also +an HTTP and HTTP/2 server, and it handles many +related features like long polling or the parsing +of most request headers. + +Can you guess how large the Cowboy codebase is, +without looking at the source? + +Do make sure you have a clear answer in your mind +before you go check. + +Good, you are back. Now what were the results? If +I am correct, you overestimated the size of Cowboy. +Cowboy is in fact about five thousand lines of code. +You probably thought it was at least ten thousand. +About eighty percent of readers will have +overestimated the size of Cowboy. And you did only +because I mentioned it can handle millions of +Websocket connections. + +Numerous studies show this effect. Just mentioning +the large number already prepared your mind to think +in that direction. Repeating the number made you +focus even more on it. Then the question asked for +a number, which ended up larger than the reality. + +The same effect can be applied to negotiation for +example. You generally want to start by giving your +offer (and not let the other party initiate) and +you want to give a really large number first. You +can also prepare your customer by mentioning an even +larger number in the previous discussion. + +And it's not just numbers either. An experiment +showed that just by looking at an image of clouds, +customers of a pillow store were buying pillows +more comfortable (and more expensive) than those +who didn't see that image. + +This is the power of associations. It is covered in +much larger detail in the books +https://www.amazon.com/Influence-Psychology-Persuasion-Robert-Cialdini/dp/006124189X[Influence] +and +https://www.amazon.com/Pre-Suasion-Revolutionary-Way-Influence-Persuade/dp/1501109790[Pre-suasion]. +I highly recommend reading those and applying what +you learn to your daily life. I'm definitely not +a professional psychologist so take this post with +a grain of salt. + +When selling Erlang, whether we are selling it to +a customer or trying to convince a developer friend +to start using it, we often talk about how Erlang +'lets you sleep at night', that it is auto healing +and always gets fantastic uptimes. + +And then we talk about 'let it crash'. + +And we describe what it means. + +We might as well just say that Erlang crashes a lot +and then take the door. It would have the same effect. +It doesn't even stop at programs crashing. You know +what else crashes? Cars, planes, trains. Often with +disastrous consequences. Is that really the message +we want to convey? + +They even https://img.youtube.com/vi/oEUBW2lCkIk/0.jpg[printed it on a t-shirt]! +Keep calm and let it crash. It's the kind of t-shirt +you probably shouldn't wear in an airport, and for good +reasons. A few people did, then realized what they were +wearing and were not too smug about it. + +And yet this is how we sell Erlang. + +A better way would be to focus on the positives, of +course, but also to make sure that those positives +are phrased in a way that prevents bad associations +to be formed in people's minds. + +Instead of 'let it crash', you can say that Erlang +has 'auto healing mechanisms'. Healing is a good +thing and accurately describes what happens in the +system. + +Should you need to go into more details, you will +probably want to avoid 'recover from crashes' and +instead say 'recover from exceptions'. Exceptions +are a pretty neutral word and, should you explain +what you mean by that, you can talk about exceptions +that occur for reasons unrelated to Erlang, like +hardware failure or network instability. + +The trick is to always use positive words and +phrases to describe Erlang, and to use external +factors to explain how Erlang deals with failures. +Never mention the failures internal to Erlang +systems unless you are asked specifically, in +which case you can say that the auto healing +applies to all exceptions. + +The 'let it crash' philosophy is great when +learning Erlang or when writing fault-tolerant +systems. But it's not going to convince anyone +to use it unless they were already looking for +it. + +Do you like this post? Tell me on Twitter. I might +make more. diff --git a/articles/cowboy-2.0.0-pre.4/index.html b/articles/cowboy-2.0.0-pre.4/index.html index 092ea08e..3ce369fb 100644 --- a/articles/cowboy-2.0.0-pre.4/index.html +++ b/articles/cowboy-2.0.0-pre.4/index.html @@ -194,6 +194,8 @@ added back.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/cowboy2-qs/index.html b/articles/cowboy2-qs/index.html index da450bf8..42343c77 100644 --- a/articles/cowboy2-qs/index.html +++ b/articles/cowboy2-qs/index.html @@ -233,6 +233,8 @@ thoughts that went into this rather than just the conclusion.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/dont-let-it-crash/index.html b/articles/dont-let-it-crash/index.html new file mode 100644 index 00000000..9fe54196 --- /dev/null +++ b/articles/dont-let-it-crash/index.html @@ -0,0 +1,281 @@ +<!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 0.17" /> + + <title>Nine Nines: Don't let it crash</title> + + <link href='https://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>Don't let it crash</span></h1> + <p class="date"> + <span class="day">22</span> + <span class="month">Jan</span> + </p> +</header> + +<div class="paragraph"><p>We have a specific mindset when writing Erlang
+programs. We focus on the normal execution of the
+program and don’t handle most of the errors that may
+occur. We sometimes call this normal execution the
+<em>happy path</em>.</p></div>
+<div class="paragraph"><p>The general pattern behind writing only for the
+<em>happy path</em>, letting the VM catch errors (writing
+them to a log for future consumption) and then
+having a supervisor restart the processes that
+failed from a clean state, has a name. We call it
+<em>let it crash</em>; and it drives many of our design
+decisions.</p></div>
+<div class="paragraph"><p>It’s a really great way to program and the results
+are fantastic compared to most other programming
+languages. And yet, <em>let it crash</em> barely convinced
+anyone that they should use Erlang. Why would that
+be?</p></div>
+<div class="paragraph"><p>You may already know that Cowboy is capable of
+handling at least 2 million Websocket connections
+on a single server. This is in large part thanks
+to the capabilities of the VM. Still, 2 million
+is good, much better than most other servers can
+do.</p></div>
+<div class="paragraph"><p>Cowboy is not just a Websocket server; it’s also
+an HTTP and HTTP/2 server, and it handles many
+related features like long polling or the parsing
+of most request headers.</p></div>
+<div class="paragraph"><p>Can you guess how large the Cowboy codebase is,
+without looking at the source?</p></div>
+<div class="paragraph"><p>Do make sure you have a clear answer in your mind
+before you go check.</p></div>
+<div class="paragraph"><p>Good, you are back. Now what were the results? If
+I am correct, you overestimated the size of Cowboy.
+Cowboy is in fact about five thousand lines of code.
+You probably thought it was at least ten thousand.
+About eighty percent of readers will have
+overestimated the size of Cowboy. And you did only
+because I mentioned it can handle millions of
+Websocket connections.</p></div>
+<div class="paragraph"><p>Numerous studies show this effect. Just mentioning
+the large number already prepared your mind to think
+in that direction. Repeating the number made you
+focus even more on it. Then the question asked for
+a number, which ended up larger than the reality.</p></div>
+<div class="paragraph"><p>The same effect can be applied to negotiation for
+example. You generally want to start by giving your
+offer (and not let the other party initiate) and
+you want to give a really large number first. You
+can also prepare your customer by mentioning an even
+larger number in the previous discussion.</p></div>
+<div class="paragraph"><p>And it’s not just numbers either. An experiment
+showed that just by looking at an image of clouds,
+customers of a pillow store were buying pillows
+more comfortable (and more expensive) than those
+who didn’t see that image.</p></div>
+<div class="paragraph"><p>This is the power of associations. It is covered in
+much larger detail in the books
+<a href="https://www.amazon.com/Influence-Psychology-Persuasion-Robert-Cialdini/dp/006124189X">Influence</a>
+and
+<a href="https://www.amazon.com/Pre-Suasion-Revolutionary-Way-Influence-Persuade/dp/1501109790">Pre-suasion</a>.
+I highly recommend reading those and applying what
+you learn to your daily life. I’m definitely not
+a professional psychologist so take this post with
+a grain of salt.</p></div>
+<div class="paragraph"><p>When selling Erlang, whether we are selling it to
+a customer or trying to convince a developer friend
+to start using it, we often talk about how Erlang
+<em>lets you sleep at night</em>, that it is auto healing
+and always gets fantastic uptimes.</p></div>
+<div class="paragraph"><p>And then we talk about <em>let it crash</em>.</p></div>
+<div class="paragraph"><p>And we describe what it means.</p></div>
+<div class="paragraph"><p>We might as well just say that Erlang crashes a lot
+and then take the door. It would have the same effect.
+It doesn’t even stop at programs crashing. You know
+what else crashes? Cars, planes, trains. Often with
+disastrous consequences. Is that really the message
+we want to convey?</p></div>
+<div class="paragraph"><p>They even <a href="https://img.youtube.com/vi/oEUBW2lCkIk/0.jpg">printed it on a t-shirt</a>!
+Keep calm and let it crash. It’s the kind of t-shirt
+you probably shouldn’t wear in an airport, and for good
+reasons. A few people did, then realized what they were
+wearing and were not too smug about it.</p></div>
+<div class="paragraph"><p>And yet this is how we sell Erlang.</p></div>
+<div class="paragraph"><p>A better way would be to focus on the positives, of
+course, but also to make sure that those positives
+are phrased in a way that prevents bad associations
+to be formed in people’s minds.</p></div>
+<div class="paragraph"><p>Instead of <em>let it crash</em>, you can say that Erlang
+has <em>auto healing mechanisms</em>. Healing is a good
+thing and accurately describes what happens in the
+system.</p></div>
+<div class="paragraph"><p>Should you need to go into more details, you will
+probably want to avoid <em>recover from crashes</em> and
+instead say <em>recover from exceptions</em>. Exceptions
+are a pretty neutral word and, should you explain
+what you mean by that, you can talk about exceptions
+that occur for reasons unrelated to Erlang, like
+hardware failure or network instability.</p></div>
+<div class="paragraph"><p>The trick is to always use positive words and
+phrases to describe Erlang, and to use external
+factors to explain how Erlang deals with failures.
+Never mention the failures internal to Erlang
+systems unless you are asked specifically, in
+which case you can say that the auto healing
+applies to all exceptions.</p></div>
+<div class="paragraph"><p>The <em>let it crash</em> philosophy is great when
+learning Erlang or when writing fault-tolerant
+systems. But it’s not going to convince anyone
+to use it unless they were already looking for
+it.</p></div>
+<div class="paragraph"><p>Do you like this post? Tell me on Twitter. I might
+make more.</p></div>
+ +</article> +</div> + +<div class="span3 sidecol"> +<h3>More articles</h3> +<ul id="articles-nav" class="extra_margin"> + + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> + + <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> + + <li><a href="https://ninenines.eu/articles/ml-archives/">Mailing list archived</a></li> + + <li><a href="https://ninenines.eu/articles/website-update/">Website update</a></li> + + <li><a href="https://ninenines.eu/articles/erlanger-playbook-september-2015-update/">The Erlanger Playbook September 2015 Update</a></li> + + <li><a href="https://ninenines.eu/articles/erlanger-playbook/">The Erlanger Playbook</a></li> + + <li><a href="https://ninenines.eu/articles/erlang-validate-utf8/">Validating UTF-8 binaries with Erlang</a></li> + + <li><a href="https://ninenines.eu/articles/on-open-source/">On open source</a></li> + + <li><a href="https://ninenines.eu/articles/the-story-so-far/">The story so far</a></li> + + <li><a href="https://ninenines.eu/articles/cowboy2-qs/">Cowboy 2.0 and query strings</a></li> + + <li><a href="https://ninenines.eu/articles/january-2014-status/">January 2014 status</a></li> + + <li><a href="https://ninenines.eu/articles/farwest-funded/">Farwest got funded!</a></li> + + <li><a href="https://ninenines.eu/articles/erlang.mk-and-relx/">Build Erlang releases with Erlang.mk and Relx</a></li> + + <li><a href="https://ninenines.eu/articles/xerl-0.5-intermediate-module/">Xerl: intermediate module</a></li> + + <li><a href="https://ninenines.eu/articles/xerl-0.4-expression-separator/">Xerl: expression separator</a></li> + + <li><a href="https://ninenines.eu/articles/erlang-scalability/">Erlang Scalability</a></li> + + <li><a href="https://ninenines.eu/articles/xerl-0.3-atomic-expressions/">Xerl: atomic expressions</a></li> + + <li><a href="https://ninenines.eu/articles/xerl-0.2-two-modules/">Xerl: two modules</a></li> + + <li><a href="https://ninenines.eu/articles/xerl-0.1-empty-modules/">Xerl: empty modules</a></li> + + <li><a href="https://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></li> + + <li><a href="https://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> + diff --git a/articles/erlang-scalability/index.html b/articles/erlang-scalability/index.html index 46871c4d..04a4c42f 100644 --- a/articles/erlang-scalability/index.html +++ b/articles/erlang-scalability/index.html @@ -218,6 +218,8 @@ concurrently.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/erlang-validate-utf8/index.html b/articles/erlang-validate-utf8/index.html index 6940ae6b..cc0068ce 100644 --- a/articles/erlang-validate-utf8/index.html +++ b/articles/erlang-validate-utf8/index.html @@ -269,6 +269,8 @@ http://www.gnu.org/software/src-highlite --> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/erlang.mk-and-relx/index.html b/articles/erlang.mk-and-relx/index.html index 0173f34a..0a966c02 100644 --- a/articles/erlang.mk-and-relx/index.html +++ b/articles/erlang.mk-and-relx/index.html @@ -172,6 +172,8 @@ containing all the flags to pass to the Erlang VM, for example <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/erlanger-playbook-september-2015-update/index.html b/articles/erlanger-playbook-september-2015-update/index.html index cb472372..0b8026b9 100644 --- a/articles/erlanger-playbook-september-2015-update/index.html +++ b/articles/erlanger-playbook-september-2015-update/index.html @@ -97,6 +97,8 @@ will be used to allow me to work on open source full time.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/erlanger-playbook/index.html b/articles/erlanger-playbook/index.html index b8345523..4ec81c34 100644 --- a/articles/erlanger-playbook/index.html +++ b/articles/erlanger-playbook/index.html @@ -150,6 +150,8 @@ You will receive updates to the book for free as soon as they are available.</p> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/farwest-funded/index.html b/articles/farwest-funded/index.html index def68b84..a3ec6011 100644 --- a/articles/farwest-funded/index.html +++ b/articles/farwest-funded/index.html @@ -105,6 +105,8 @@ can help!</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/index.html b/articles/index.html index b1edcd8a..9e473f54 100644 --- a/articles/index.html +++ b/articles/index.html @@ -74,6 +74,23 @@ <article class="blog_item"> <header> + <h2><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></h2> + <p class="date"> + <span class="day">22</span> + <span class="month">Jan</span> + </p> + </header> + + <p>We have a specific mindset when writing Erlang
programs. We focus on the normal execution of the
program and don’t handle most of the errors that may
occur. We sometimes call this normal execution the
happy path. +
The general pattern behind writing only for the
happy path, letting the VM catch errors (writing
them to a log for future consumption) and then
having a supervisor restart the processes that
failed from a clean state, has a name.</p> + + <p style="text-align:right"> + <a class="read_more" href="https://ninenines.eu/articles/dont-let-it-crash/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> <h2><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></h2> <p class="date"> <span class="day">03</span> @@ -415,23 +432,6 @@ </p> </article> - <article class="blog_item"> - <header> - <h2><a href="https://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></h2> - <p class="date"> - <span class="day">14</span> - <span class="month">Nov</span> - </p> - </header> - - <p>Last week I was speaking at the
London Erlang Factory Lite
where I presented a live demonstration of building an FTP server using
Ranch.
As there was no slide, you should use this article as a reference instead. -
The goal of this article is to showcase how to use Ranch for writing
a network protocol implementation, how Ranch gets out of the way to let
you write the code that matters, and the common techniques used when
writing servers.</p> - - <p style="text-align:right"> - <a class="read_more" href="https://ninenines.eu/articles/ranch-ftp/">Read More</a> - </p> - </article> - <nav class="pagination" role="pagination"> diff --git a/articles/index.xml b/articles/index.xml index 40507060..dbb9bb8f 100644 --- a/articles/index.xml +++ b/articles/index.xml @@ -6,10 +6,131 @@ <description>Recent content in Articles-rsses on Nine Nines</description> <generator>Hugo -- gohugo.io</generator> <language>en-us</language> - <lastBuildDate>Tue, 03 Jan 2017 00:00:00 +0100</lastBuildDate> + <lastBuildDate>Sun, 22 Jan 2017 00:00:00 +0100</lastBuildDate> <atom:link href="https://ninenines.eu/articles/index.xml" rel="self" type="application/rss+xml" /> <item> + <title>Don't let it crash</title> + <link>https://ninenines.eu/articles/dont-let-it-crash/</link> + <pubDate>Sun, 22 Jan 2017 00:00:00 +0100</pubDate> + + <guid>https://ninenines.eu/articles/dont-let-it-crash/</guid> + <description><div class="paragraph"><p>We have a specific mindset when writing Erlang
+programs. We focus on the normal execution of the
+program and don&#8217;t handle most of the errors that may
+occur. We sometimes call this normal execution the
+<em>happy path</em>.</p></div>
+<div class="paragraph"><p>The general pattern behind writing only for the
+<em>happy path</em>, letting the VM catch errors (writing
+them to a log for future consumption) and then
+having a supervisor restart the processes that
+failed from a clean state, has a name. We call it
+<em>let it crash</em>; and it drives many of our design
+decisions.</p></div>
+<div class="paragraph"><p>It&#8217;s a really great way to program and the results
+are fantastic compared to most other programming
+languages. And yet, <em>let it crash</em> barely convinced
+anyone that they should use Erlang. Why would that
+be?</p></div>
+<div class="paragraph"><p>You may already know that Cowboy is capable of
+handling at least 2 million Websocket connections
+on a single server. This is in large part thanks
+to the capabilities of the VM. Still, 2 million
+is good, much better than most other servers can
+do.</p></div>
+<div class="paragraph"><p>Cowboy is not just a Websocket server; it&#8217;s also
+an HTTP and HTTP/2 server, and it handles many
+related features like long polling or the parsing
+of most request headers.</p></div>
+<div class="paragraph"><p>Can you guess how large the Cowboy codebase is,
+without looking at the source?</p></div>
+<div class="paragraph"><p>Do make sure you have a clear answer in your mind
+before you go check.</p></div>
+<div class="paragraph"><p>Good, you are back. Now what were the results? If
+I am correct, you overestimated the size of Cowboy.
+Cowboy is in fact about five thousand lines of code.
+You probably thought it was at least ten thousand.
+About eighty percent of readers will have
+overestimated the size of Cowboy. And you did only
+because I mentioned it can handle millions of
+Websocket connections.</p></div>
+<div class="paragraph"><p>Numerous studies show this effect. Just mentioning
+the large number already prepared your mind to think
+in that direction. Repeating the number made you
+focus even more on it. Then the question asked for
+a number, which ended up larger than the reality.</p></div>
+<div class="paragraph"><p>The same effect can be applied to negotiation for
+example. You generally want to start by giving your
+offer (and not let the other party initiate) and
+you want to give a really large number first. You
+can also prepare your customer by mentioning an even
+larger number in the previous discussion.</p></div>
+<div class="paragraph"><p>And it&#8217;s not just numbers either. An experiment
+showed that just by looking at an image of clouds,
+customers of a pillow store were buying pillows
+more comfortable (and more expensive) than those
+who didn&#8217;t see that image.</p></div>
+<div class="paragraph"><p>This is the power of associations. It is covered in
+much larger detail in the books
+<a href="https://www.amazon.com/Influence-Psychology-Persuasion-Robert-Cialdini/dp/006124189X">Influence</a>
+and
+<a href="https://www.amazon.com/Pre-Suasion-Revolutionary-Way-Influence-Persuade/dp/1501109790">Pre-suasion</a>.
+I highly recommend reading those and applying what
+you learn to your daily life. I&#8217;m definitely not
+a professional psychologist so take this post with
+a grain of salt.</p></div>
+<div class="paragraph"><p>When selling Erlang, whether we are selling it to
+a customer or trying to convince a developer friend
+to start using it, we often talk about how Erlang
+<em>lets you sleep at night</em>, that it is auto healing
+and always gets fantastic uptimes.</p></div>
+<div class="paragraph"><p>And then we talk about <em>let it crash</em>.</p></div>
+<div class="paragraph"><p>And we describe what it means.</p></div>
+<div class="paragraph"><p>We might as well just say that Erlang crashes a lot
+and then take the door. It would have the same effect.
+It doesn&#8217;t even stop at programs crashing. You know
+what else crashes? Cars, planes, trains. Often with
+disastrous consequences. Is that really the message
+we want to convey?</p></div>
+<div class="paragraph"><p>They even <a href="https://img.youtube.com/vi/oEUBW2lCkIk/0.jpg">printed it on a t-shirt</a>!
+Keep calm and let it crash. It&#8217;s the kind of t-shirt
+you probably shouldn&#8217;t wear in an airport, and for good
+reasons. A few people did, then realized what they were
+wearing and were not too smug about it.</p></div>
+<div class="paragraph"><p>And yet this is how we sell Erlang.</p></div>
+<div class="paragraph"><p>A better way would be to focus on the positives, of
+course, but also to make sure that those positives
+are phrased in a way that prevents bad associations
+to be formed in people&#8217;s minds.</p></div>
+<div class="paragraph"><p>Instead of <em>let it crash</em>, you can say that Erlang
+has <em>auto healing mechanisms</em>. Healing is a good
+thing and accurately describes what happens in the
+system.</p></div>
+<div class="paragraph"><p>Should you need to go into more details, you will
+probably want to avoid <em>recover from crashes</em> and
+instead say <em>recover from exceptions</em>. Exceptions
+are a pretty neutral word and, should you explain
+what you mean by that, you can talk about exceptions
+that occur for reasons unrelated to Erlang, like
+hardware failure or network instability.</p></div>
+<div class="paragraph"><p>The trick is to always use positive words and
+phrases to describe Erlang, and to use external
+factors to explain how Erlang deals with failures.
+Never mention the failures internal to Erlang
+systems unless you are asked specifically, in
+which case you can say that the auto healing
+applies to all exceptions.</p></div>
+<div class="paragraph"><p>The <em>let it crash</em> philosophy is great when
+learning Erlang or when writing fault-tolerant
+systems. But it&#8217;s not going to convince anyone
+to use it unless they were already looking for
+it.</p></div>
+<div class="paragraph"><p>Do you like this post? Tell me on Twitter. I might
+make more.</p></div>
+</description> + </item> + + <item> <title>Cowboy 2.0 pre-release 4</title> <link>https://ninenines.eu/articles/cowboy-2.0.0-pre.4/</link> <pubDate>Tue, 03 Jan 2017 00:00:00 +0100</pubDate> @@ -1527,66 +1648,5 @@ http://www.gnu.org/software/src-highlite --> </description> </item> - <item> - <title>Xerl: expression separator</title> - <link>https://ninenines.eu/articles/xerl-0.4-expression-separator/</link> - <pubDate>Fri, 01 Mar 2013 00:00:00 +0100</pubDate> - - <guid>https://ninenines.eu/articles/xerl-0.4-expression-separator/</guid> - <description><div class="paragraph"><p>As promised we are adding an expression separator this time.
-This will be short and easy.</p></div>
-<div class="paragraph"><p>In the tokenizer we only need to add a line recognizing the
-comma as a valid token.</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt>, <span style="color: #990000">:</span> {<span style="color: #FF6600">token</span>, {<span style="color: #FF6600">','</span>, <span style="color: #009900">TokenLine</span>}}<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>Then we need to change the following lines in the parser:</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
-<span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$2'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>And add a comma between the expressions on the second line:</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span>
-<span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">','</span> <span style="color: #FF6600">exprs</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span> | <span style="color: #FF6600">'$3'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>That takes care of everything except the optional trailing
-comma at the end of our lists of expressions. We just need an
-additional rule to take care of this.</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="color: #FF6600">exprs</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">expr</span> <span style="color: #FF6600">','</span> <span style="color: #990000">:</span> [<span style="color: #FF6600">'$1'</span>]<span style="color: #990000">.</span></tt></pre></div></div>
-<div class="paragraph"><p>That&#8217;s it.</p></div>
-<div class="paragraph"><p>Wondering why we don&#8217;t have this optional trailing comma in
-Erlang considering how easy it was and the number of people
-complaining about it? Yeah, me too. But that&#8217;s for someone else
-to answer.</p></div>
-<div class="paragraph"><p>Another change I want to talk about is a simple modification
-of the compiler code to use an <code>#env{}</code> record for
-tracking state instead of passing around individual variables.
-This will be required later on when we make modules into proper
-expressions so I thought it was a good idea to anticipate.</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-<a href="https://github.com/extend/xerl/blob/0.4/">View the source</a>
-</p>
-</li>
-</ul></div>
-</description> - </item> - </channel> </rss>
\ No newline at end of file diff --git a/articles/january-2014-status/index.html b/articles/january-2014-status/index.html index 24fc69a2..da0a5b8d 100644 --- a/articles/january-2014-status/index.html +++ b/articles/january-2014-status/index.html @@ -224,6 +224,8 @@ the sponsoring idea, anything really! Thanks.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/ml-archives/index.html b/articles/ml-archives/index.html index 41a87cb2..6284b2d5 100644 --- a/articles/ml-archives/index.html +++ b/articles/ml-archives/index.html @@ -94,6 +94,8 @@ underlying problem in the project or its documentation.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/on-open-source/index.html b/articles/on-open-source/index.html index 66387794..a21b30eb 100644 --- a/articles/on-open-source/index.html +++ b/articles/on-open-source/index.html @@ -201,6 +201,8 @@ of your company’s money.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/page/2/index.html b/articles/page/2/index.html index 694bed10..b7448109 100644 --- a/articles/page/2/index.html +++ b/articles/page/2/index.html @@ -74,6 +74,23 @@ <article class="blog_item"> <header> + <h2><a href="https://ninenines.eu/articles/ranch-ftp/">Build an FTP Server with Ranch in 30 Minutes</a></h2> + <p class="date"> + <span class="day">14</span> + <span class="month">Nov</span> + </p> + </header> + + <p>Last week I was speaking at the
London Erlang Factory Lite
where I presented a live demonstration of building an FTP server using
Ranch.
As there was no slide, you should use this article as a reference instead. +
The goal of this article is to showcase how to use Ranch for writing
a network protocol implementation, how Ranch gets out of the way to let
you write the code that matters, and the common techniques used when
writing servers.</p> + + <p style="text-align:right"> + <a class="read_more" href="https://ninenines.eu/articles/ranch-ftp/">Read More</a> + </p> + </article> + + <article class="blog_item"> + <header> <h2><a href="https://ninenines.eu/articles/tictactoe/">Erlang Tic Tac Toe</a></h2> <p class="date"> <span class="day">17</span> diff --git a/articles/ranch-1.3/index.html b/articles/ranch-1.3/index.html index 6286a77d..8e182a0e 100644 --- a/articles/ranch-1.3/index.html +++ b/articles/ranch-1.3/index.html @@ -166,6 +166,8 @@ that need fixing sooner rather than later.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/ranch-ftp/index.html b/articles/ranch-ftp/index.html index 307deea8..f20cefcc 100644 --- a/articles/ranch-ftp/index.html +++ b/articles/ranch-ftp/index.html @@ -294,6 +294,8 @@ binary protocol implementations in just a few lines of code.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/the-story-so-far/index.html b/articles/the-story-so-far/index.html index 9d01ab67..2e6d1db6 100644 --- a/articles/the-story-so-far/index.html +++ b/articles/the-story-so-far/index.html @@ -308,6 +308,8 @@ project and make sure it doesn’t happen again.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/tictactoe/index.html b/articles/tictactoe/index.html index a96fda88..dfeff96b 100644 --- a/articles/tictactoe/index.html +++ b/articles/tictactoe/index.html @@ -167,6 +167,8 @@ of writing algorithms to do things.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/website-update/index.html b/articles/website-update/index.html index 9f20a0ba..aa890a89 100644 --- a/articles/website-update/index.html +++ b/articles/website-update/index.html @@ -141,6 +141,8 @@ upgrading JS libraries.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/xerl-0.1-empty-modules/index.html b/articles/xerl-0.1-empty-modules/index.html index d8c103d3..1fb11ce7 100644 --- a/articles/xerl-0.1-empty-modules/index.html +++ b/articles/xerl-0.1-empty-modules/index.html @@ -222,6 +222,8 @@ the next few articles.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/xerl-0.2-two-modules/index.html b/articles/xerl-0.2-two-modules/index.html index b5979ee5..9651e83a 100644 --- a/articles/xerl-0.2-two-modules/index.html +++ b/articles/xerl-0.2-two-modules/index.html @@ -227,6 +227,8 @@ though, so let’s get back to it after we add more.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/xerl-0.3-atomic-expressions/index.html b/articles/xerl-0.3-atomic-expressions/index.html index d34c591e..32e6fc1c 100644 --- a/articles/xerl-0.3-atomic-expressions/index.html +++ b/articles/xerl-0.3-atomic-expressions/index.html @@ -231,6 +231,8 @@ do that.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/xerl-0.4-expression-separator/index.html b/articles/xerl-0.4-expression-separator/index.html index 55c68ce1..039ff166 100644 --- a/articles/xerl-0.4-expression-separator/index.html +++ b/articles/xerl-0.4-expression-separator/index.html @@ -136,6 +136,8 @@ expressions so I thought it was a good idea to anticipate.</p></div> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/articles/xerl-0.5-intermediate-module/index.html b/articles/xerl-0.5-intermediate-module/index.html index c12c6ce7..be22f0d4 100644 --- a/articles/xerl-0.5-intermediate-module/index.html +++ b/articles/xerl-0.5-intermediate-module/index.html @@ -214,6 +214,8 @@ http://www.gnu.org/software/src-highlite --> <h3>More articles</h3> <ul id="articles-nav" class="extra_margin"> + <li><a href="https://ninenines.eu/articles/dont-let-it-crash/">Don't let it crash</a></li> + <li><a href="https://ninenines.eu/articles/cowboy-2.0.0-pre.4/">Cowboy 2.0 pre-release 4</a></li> <li><a href="https://ninenines.eu/articles/ranch-1.3/">Ranch 1.3</a></li> diff --git a/docs/en/erlang.mk/1/guide/app.asciidoc b/docs/en/erlang.mk/1/guide/app.asciidoc index 229ce973..94f8eb1a 100644 --- a/docs/en/erlang.mk/1/guide/app.asciidoc +++ b/docs/en/erlang.mk/1/guide/app.asciidoc @@ -284,6 +284,17 @@ include erlang.mk ERLC_OPTS := $(filter-out -Werror,$(ERLC_OPTS)) ---- +==== ERLC_ASN1_OPTS + +`ERLC_ASN1_OPTS` can be used to pass compiler options when compiling +ASN.1 files. Please refer to the +http://erlang.org/doc/man/asn1ct.html[asn1ct manual] for the full list. + +By default, Erlang.mk will leave this empty. + +You can redefine this variable in your Makefile. +Please see the `ERLC_OPTS` section for instructions. + ==== ERLC_EXCLUDE `ERLC_EXCLUDE` can be used to exclude some modules from the diff --git a/docs/en/erlang.mk/1/guide/app/index.html b/docs/en/erlang.mk/1/guide/app/index.html index b6fbf4f7..b05e48c4 100644 --- a/docs/en/erlang.mk/1/guide/app/index.html +++ b/docs/en/erlang.mk/1/guide/app/index.html @@ -471,6 +471,15 @@ sets, by defining ERLC_OPTS after including Erlang.mk using the <div class="content"></div></div>
</div>
<div class="sect3">
+<h4 id="_erlc_asn1_opts">ERLC_ASN1_OPTS</h4>
+<div class="paragraph"><p><code>ERLC_ASN1_OPTS</code> can be used to pass compiler options when compiling
+ASN.1 files. Please refer to the
+<a href="http://erlang.org/doc/man/asn1ct.html">asn1ct manual</a> for the full list.</p></div>
+<div class="paragraph"><p>By default, Erlang.mk will leave this empty.</p></div>
+<div class="paragraph"><p>You can redefine this variable in your Makefile.
+Please see the <code>ERLC_OPTS</code> section for instructions.</p></div>
+</div>
+<div class="sect3">
<h4 id="_erlc_exclude">ERLC_EXCLUDE</h4>
<div class="paragraph"><p><code>ERLC_EXCLUDE</code> can be used to exclude some modules from the
compilation. It’s there for handling special cases, you should
diff --git a/donate/index.html b/donate/index.html index 7db11691..c3e254e8 100644 --- a/donate/index.html +++ b/donate/index.html @@ -105,6 +105,8 @@ and Erlang.mk is fantastic:</p></div> + + <div class="sect2">
<h3 id="_like_my_work_donate">Like my work? Donate!</h3>
<div class="paragraph"><p>Donate to Loïc Hoguin because his work on Cowboy
@@ -263,6 +263,8 @@ + + <div class="paragraph"><p>The Erlanger Playbook is now available!<br />
<a href="/articles/erlanger-playbook">Buy now</a> — <a href="/services">Become a Cowboy project sponsor</a></p></div>
@@ -6,10 +6,131 @@ <description>Recent content on Nine Nines</description> <generator>Hugo -- gohugo.io</generator> <language>en-us</language> - <lastBuildDate>Tue, 03 Jan 2017 00:00:00 +0100</lastBuildDate> + <lastBuildDate>Sun, 22 Jan 2017 00:00:00 +0100</lastBuildDate> <atom:link href="https://ninenines.eu/index.xml" rel="self" type="application/rss+xml" /> <item> + <title>Don't let it crash</title> + <link>https://ninenines.eu/articles/dont-let-it-crash/</link> + <pubDate>Sun, 22 Jan 2017 00:00:00 +0100</pubDate> + + <guid>https://ninenines.eu/articles/dont-let-it-crash/</guid> + <description><div class="paragraph"><p>We have a specific mindset when writing Erlang
+programs. We focus on the normal execution of the
+program and don&#8217;t handle most of the errors that may
+occur. We sometimes call this normal execution the
+<em>happy path</em>.</p></div>
+<div class="paragraph"><p>The general pattern behind writing only for the
+<em>happy path</em>, letting the VM catch errors (writing
+them to a log for future consumption) and then
+having a supervisor restart the processes that
+failed from a clean state, has a name. We call it
+<em>let it crash</em>; and it drives many of our design
+decisions.</p></div>
+<div class="paragraph"><p>It&#8217;s a really great way to program and the results
+are fantastic compared to most other programming
+languages. And yet, <em>let it crash</em> barely convinced
+anyone that they should use Erlang. Why would that
+be?</p></div>
+<div class="paragraph"><p>You may already know that Cowboy is capable of
+handling at least 2 million Websocket connections
+on a single server. This is in large part thanks
+to the capabilities of the VM. Still, 2 million
+is good, much better than most other servers can
+do.</p></div>
+<div class="paragraph"><p>Cowboy is not just a Websocket server; it&#8217;s also
+an HTTP and HTTP/2 server, and it handles many
+related features like long polling or the parsing
+of most request headers.</p></div>
+<div class="paragraph"><p>Can you guess how large the Cowboy codebase is,
+without looking at the source?</p></div>
+<div class="paragraph"><p>Do make sure you have a clear answer in your mind
+before you go check.</p></div>
+<div class="paragraph"><p>Good, you are back. Now what were the results? If
+I am correct, you overestimated the size of Cowboy.
+Cowboy is in fact about five thousand lines of code.
+You probably thought it was at least ten thousand.
+About eighty percent of readers will have
+overestimated the size of Cowboy. And you did only
+because I mentioned it can handle millions of
+Websocket connections.</p></div>
+<div class="paragraph"><p>Numerous studies show this effect. Just mentioning
+the large number already prepared your mind to think
+in that direction. Repeating the number made you
+focus even more on it. Then the question asked for
+a number, which ended up larger than the reality.</p></div>
+<div class="paragraph"><p>The same effect can be applied to negotiation for
+example. You generally want to start by giving your
+offer (and not let the other party initiate) and
+you want to give a really large number first. You
+can also prepare your customer by mentioning an even
+larger number in the previous discussion.</p></div>
+<div class="paragraph"><p>And it&#8217;s not just numbers either. An experiment
+showed that just by looking at an image of clouds,
+customers of a pillow store were buying pillows
+more comfortable (and more expensive) than those
+who didn&#8217;t see that image.</p></div>
+<div class="paragraph"><p>This is the power of associations. It is covered in
+much larger detail in the books
+<a href="https://www.amazon.com/Influence-Psychology-Persuasion-Robert-Cialdini/dp/006124189X">Influence</a>
+and
+<a href="https://www.amazon.com/Pre-Suasion-Revolutionary-Way-Influence-Persuade/dp/1501109790">Pre-suasion</a>.
+I highly recommend reading those and applying what
+you learn to your daily life. I&#8217;m definitely not
+a professional psychologist so take this post with
+a grain of salt.</p></div>
+<div class="paragraph"><p>When selling Erlang, whether we are selling it to
+a customer or trying to convince a developer friend
+to start using it, we often talk about how Erlang
+<em>lets you sleep at night</em>, that it is auto healing
+and always gets fantastic uptimes.</p></div>
+<div class="paragraph"><p>And then we talk about <em>let it crash</em>.</p></div>
+<div class="paragraph"><p>And we describe what it means.</p></div>
+<div class="paragraph"><p>We might as well just say that Erlang crashes a lot
+and then take the door. It would have the same effect.
+It doesn&#8217;t even stop at programs crashing. You know
+what else crashes? Cars, planes, trains. Often with
+disastrous consequences. Is that really the message
+we want to convey?</p></div>
+<div class="paragraph"><p>They even <a href="https://img.youtube.com/vi/oEUBW2lCkIk/0.jpg">printed it on a t-shirt</a>!
+Keep calm and let it crash. It&#8217;s the kind of t-shirt
+you probably shouldn&#8217;t wear in an airport, and for good
+reasons. A few people did, then realized what they were
+wearing and were not too smug about it.</p></div>
+<div class="paragraph"><p>And yet this is how we sell Erlang.</p></div>
+<div class="paragraph"><p>A better way would be to focus on the positives, of
+course, but also to make sure that those positives
+are phrased in a way that prevents bad associations
+to be formed in people&#8217;s minds.</p></div>
+<div class="paragraph"><p>Instead of <em>let it crash</em>, you can say that Erlang
+has <em>auto healing mechanisms</em>. Healing is a good
+thing and accurately describes what happens in the
+system.</p></div>
+<div class="paragraph"><p>Should you need to go into more details, you will
+probably want to avoid <em>recover from crashes</em> and
+instead say <em>recover from exceptions</em>. Exceptions
+are a pretty neutral word and, should you explain
+what you mean by that, you can talk about exceptions
+that occur for reasons unrelated to Erlang, like
+hardware failure or network instability.</p></div>
+<div class="paragraph"><p>The trick is to always use positive words and
+phrases to describe Erlang, and to use external
+factors to explain how Erlang deals with failures.
+Never mention the failures internal to Erlang
+systems unless you are asked specifically, in
+which case you can say that the auto healing
+applies to all exceptions.</p></div>
+<div class="paragraph"><p>The <em>let it crash</em> philosophy is great when
+learning Erlang or when writing fault-tolerant
+systems. But it&#8217;s not going to convince anyone
+to use it unless they were already looking for
+it.</p></div>
+<div class="paragraph"><p>Do you like this post? Tell me on Twitter. I might
+make more.</p></div>
+</description> + </item> + + <item> <title>Cowboy 2.0 pre-release 4</title> <link>https://ninenines.eu/articles/cowboy-2.0.0-pre.4/</link> <pubDate>Tue, 03 Jan 2017 00:00:00 +0100</pubDate> @@ -1132,163 +1253,5 @@ project and make sure it doesn&#8217;t happen again.</p></div> </description> </item> - <item> - <title>Cowboy 2.0 and query strings</title> - <link>https://ninenines.eu/articles/cowboy2-qs/</link> - <pubDate>Wed, 20 Aug 2014 00:00:00 +0100</pubDate> - - <guid>https://ninenines.eu/articles/cowboy2-qs/</guid> - <description><div class="paragraph"><p>Now that Cowboy 1.0 is out, I can spend some of my time thinking
-about Cowboy 2.0 that will be released soon after Erlang/OTP 18.0.
-This entry discusses the proposed changes to query string handling
-in Cowboy.</p></div>
-<div class="paragraph"><p>Cowboy 2.0 will respond to user wishes by simplifying the interface
-of the <code>cowboy_req</code> module. Users want two things: less
-juggling with the Req variable, and more maps. Maps is the only
-dynamic key/value data structure in Erlang that we can match directly
-to extract values, allowing users to greatly simplify their code as
-they don&#8217;t need to call functions to do everything anymore.</p></div>
-<div class="paragraph"><p>Query strings are a good candidate for maps. It&#8217;s a list of
-key/values, so it&#8217;s pretty obvious we can win a lot by using maps.
-However query strings have one difference with maps: they can have
-duplicate keys.</p></div>
-<div class="paragraph"><p>How are we expected to handle duplicate keys? There&#8217;s no standard
-behavior. It&#8217;s up to applications. And looking at what is done in
-the wild, there&#8217;s no de facto standard either. While some ignore
-duplicate keys (keeping the first or the last they find), others
-require duplicate keys to end with <code>[]</code> to automatically
-put the values in a list, or even worse, languages like PHP even
-allow you to do things like <code>key[something][other]</code> and
-create a deep structure for it. Finally some allow any key to have
-duplicates and just gives you lists of key/values.</p></div>
-<div class="paragraph"><p>Cowboy so far had functions to retrieve query string values one
-value at a time, and if there were duplicates it would return the
-first it finds. It also has a function returning the entire list
-with all duplicates, allowing you to filter it to get all of them,
-and another function that returns the raw query string.</p></div>
-<div class="paragraph"><p>What are duplicates used for? Not that many things actually.</p></div>
-<div class="paragraph"><p>One use of duplicate keys is with HTML forms. It is common practice
-to give all related checkboxes the same name so you get a list of
-what&#8217;s been checked. When nothing is checked, nothing is sent at all,
-the key is not in the list.</p></div>
-<div class="paragraph"><p>Another use of duplicate keys is when generating forms. A good
-example of that would be a form that allows uploading any number
-of files. When you add a file, client-side code adds another field
-to the form. Repeat up to a certain limit.</p></div>
-<div class="paragraph"><p>And that&#8217;s about it. Of note is that HTML radio elements share
-the same name too, but only one key/value is sent, so they are not
-relevant here.</p></div>
-<div class="paragraph"><p>Normally this would be the part where I tell you how we solve
-this elegantly. But I had doubts. Why? Because there&#8217;s no good
-solutions to solving only this particular problem.</p></div>
-<div class="paragraph"><p>I then stopped thinking about duplicate keys for a minute and
-started to think about the larger problem.</p></div>
-<div class="paragraph"><p>Query strings are input data. They take a particular form,
-and may be sent as part of the URI or as part of the request
-body. We have other kinds of input data. We have headers and
-cookies and the request body in various forms. We also have
-path segments in URIs.</p></div>
-<div class="paragraph"><p>What do you do with input data? Well you use it to do
-something. But there is one thing that you almost always do
-(and if you don&#8217;t, you really should): you validate it and
-you map it into Erlang terms.</p></div>
-<div class="paragraph"><p>Cowboy left the user take care of validation and conversion
-into Erlang terms so far. Rather, it left the user take care
-of it everywhere except one place. Guess where? That&#8217;s right,
-bindings.</p></div>
-<div class="paragraph"><p>If you define routes with bindings then you have the option
-to provide constraints. Constraints can be used to do two things:
-validate the data and convert it in a more appropriate term. For
-example if you use the <code>int</code> constraint, Cowboy will
-make sure the binding is an integer, and will replace the value
-with the integer representation so that you can use it directly.
-In this particular case it not only routes the URI, but also
-validates and converts the bindings directly.</p></div>
-<div class="paragraph"><p>This is very relevant in the case of our duplicate keys,
-because if we have a list with duplicates of a key, chances
-are we want to convert that into a list of Erlang terms, and
-also make sure that all the elements in this list are expected.</p></div>
-<div class="paragraph"><p>The answer to this particular problem is simple. We need a
-function that will parse the query string and apply constraints.
-But this is not all, there is one other problem to be solved.</p></div>
-<div class="paragraph"><p>The other problem is that for the user some keys are mandatory
-and some are optional. Optional keys include the ones that
-correspond to HTML checkboxes: if the key for one or more
-checkbox is missing from the query string, we still want to
-have an empty list in our map so we can easily match. Matching
-maps is great, but not so much when values might be missing,
-so we have to normalize this data a little.</p></div>
-<div class="paragraph"><p>This problem is solved by allowing a default value. If the
-key is missing and a default exists, set it. If no default
-exists, then the key was mandatory and we want to crash.</p></div>
-<div class="paragraph"><p>I therefore make a proposal for changing the query string
-interface to three functions.</p></div>
-<div class="paragraph"><p>The first function already exists, it is <code>cowboy_req:qs(Req)</code>
-and it returns only the query string binary. No more Req returned.</p></div>
-<div class="paragraph"><p>The second function is a renaming of <code>cowboy_req:qs_vals(Req)</code>
-to something more explicit: <code>cowboy_req:parse_qs(Req)</code>.
-The new name implies that a parsing operation is done. It was implicit
-and cached before. It will be explicit and not cached anymore now.
-Again, no more Req returned.</p></div>
-<div class="paragraph"><p>The third function is the one I mentioned above. I think
-the interface <code>cowboy_req:match_qs(Req, Fields)</code> is
-most appropriate. It returns a normalized map that is the same
-regardless of optional fields being provided with the request,
-allowing for easy matching. It crashes if something went wrong.
-Still no Req returned.</p></div>
-<div class="paragraph"><p>I feel that this three function interface provides everything
-one would need to comfortably write applications. You can get
-low level and get the query string directly; you can get a list
-of key/value binaries without any additional processing and do it
-on your own; or you can get a processed map that contains Erlang
-terms ready to be used.</p></div>
-<div class="paragraph"><p>I strongly believe that by democratizing the constraints to
-more than just bindings, but also to query string, cookies and
-other key/values in Cowboy, we can allow the developer to quickly
-and easily go from HTTP request to Erlang function calls. The
-constraints are reusable functions that can serve as guards
-against unwanted data, providing convenience in the process.</p></div>
-<div class="paragraph"><p>Your handlers will not look like an endless series of calls
-to get and convert the input data, they will instead be just
-one call at the beginning followed by the actual application
-logic, thanks to constraints and maps.</p></div>
-<div class="listingblock">
-<div class="content"><!-- Generator: GNU source-highlight 3.1.8
-by Lorenzo Bettini
-http://www.lorenzobettini.it
-http://www.gnu.org/software/src-highlite -->
-<pre><tt><span style="font-weight: bold"><span style="color: #000000">handle</span></span>(<span style="color: #009900">Req</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-&gt;</span>
- #{<span style="color: #FF6600">name</span><span style="color: #990000">:=</span><span style="color: #009900">Name</span>, <span style="color: #FF6600">email</span><span style="color: #990000">:=</span><span style="color: #009900">Email</span>, <span style="color: #FF6600">choices</span><span style="color: #990000">:=</span><span style="color: #009900">ChoicesList</span>, <span style="color: #FF6600">remember_me</span><span style="color: #990000">:=</span><span style="color: #009900">RememberMe</span>} <span style="color: #990000">=</span>
- <span style="font-weight: bold"><span style="color: #000000">cowboy_req:match_qs</span></span>(<span style="color: #009900">Req</span>, [
- <span style="font-weight: bold"><span style="color: #000080">name</span></span>, {<span style="color: #FF6600">email</span>, <span style="color: #FF6600">email</span>},
- {<span style="color: #FF6600">choices</span>, <span style="font-weight: bold"><span style="color: #0000FF">fun</span></span> <span style="font-weight: bold"><span style="color: #000000">check_choices</span></span><span style="color: #990000">/</span><span style="color: #993399">1</span>, []},
- {<span style="color: #FF6600">remember_me</span>, <span style="color: #FF6600">boolean</span>, <span style="color: #000080">false</span>}]),
- <span style="font-weight: bold"><span style="color: #000000">save_choices</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Email</span>, <span style="color: #009900">ChoicesList</span>),
- <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #009900">RememberMe</span> <span style="color: #990000">-&gt;</span> <span style="font-weight: bold"><span style="color: #000000">create_account</span></span>(<span style="color: #009900">Name</span>, <span style="color: #009900">Email</span>); <span style="color: #000080">true</span> <span style="color: #990000">-&gt;</span> <span style="color: #FF6600">ok</span> <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>,
- {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>}<span style="color: #990000">.</span>
-
-<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000">&lt;&lt;</span><span style="color: #FF0000">"blue"</span><span style="color: #990000">&gt;&gt;</span>) <span style="color: #990000">-&gt;</span> {<span style="color: #000080">true</span>, <span style="color: #FF6600">blue</span>};
-<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000">&lt;&lt;</span><span style="color: #FF0000">"red"</span><span style="color: #990000">&gt;&gt;</span>) <span style="color: #990000">-&gt;</span> {<span style="color: #000080">true</span>, <span style="color: #FF6600">red</span>};
-<span style="font-weight: bold"><span style="color: #000000">check_choices</span></span>(<span style="color: #990000">_</span>) <span style="color: #990000">-&gt;</span> <span style="color: #000080">false</span>;</tt></pre></div></div>
-<div class="paragraph"><p>(Don&#8217;t look too closely at the structure yet.)</p></div>
-<div class="paragraph"><p>As you can see in the above snippet, it becomes really easy
-to go from query string to values. You can also use the map
-directly as it is guaranteed to only contain the keys you
-specified, any extra key is not returned.</p></div>
-<div class="paragraph"><p>This would I believe be a huge step up as we can now
-focus on writing applications instead of translating HTTP
-calls. Cowboy can now take care of it.</p></div>
-<div class="paragraph"><p>And to conclude, this also solves our duplicate keys
-dilemma, as they now automatically become a list of binaries,
-and this list is then checked against constraints that
-will fail if they were not expecting a list. And in the
-example above, it even converts the values to atoms for
-easier manipulation.</p></div>
-<div class="paragraph"><p>As usual, feedback is more than welcome, and I apologize
-for the rocky structure of this post as it contains all the
-thoughts that went into this rather than just the conclusion.</p></div>
-</description> - </item> - </channel> </rss>
\ No newline at end of file diff --git a/services/index.html b/services/index.html index e2c1d536..1ebc9586 100644 --- a/services/index.html +++ b/services/index.html @@ -190,6 +190,8 @@ the same restrictions apply.</p></div> + + <div class="sect2">
<h3 id="_like_my_work_donate">Like my work? Donate!</h3>
<div class="paragraph"><p>Donate to Loïc Hoguin because his work on Cowboy
diff --git a/sitemap.xml b/sitemap.xml index 2a0c4d64..d70c57e2 100644 --- a/sitemap.xml +++ b/sitemap.xml @@ -3,7 +3,12 @@ <url> <loc>https://ninenines.eu/</loc> - <lastmod>2017-01-03T00:00:00+01:00</lastmod> + <lastmod>2017-01-22T00:00:00+01:00</lastmod> + </url> + + <url> + <loc>https://ninenines.eu/articles/dont-let-it-crash/</loc> + <lastmod>2017-01-22T00:00:00+01:00</lastmod> </url> <url> |