Scala, Javascript vs Craftsmanship

Installation facile de vagrant sur OSX

J’ai eu l’occasion de travailler un peu avec Vagrant ces dernier temps. L’installation sur OS X peut être assez compliquée, je vous livre ici la recette la plus simple que j’ai trouvé.

Premièrement, installez Homebrew

Si vous n’avez pas encore installé Homebrew, il est grand temps de le faire. Je vous promet que vous ne le regretterez pas. Homebrew est très propre et installe ses logiciels dans /usr/local/Cellar/ puis crée des liens symboliques vers les logiciels dans /usr/local/bin. Aucune “pollution” du système n’est a craindre.

L’installation de homebrew lui-même est très simple:

ruby -e "$(curl -fsSL"

Deuxièmement, installez Vagrant

Avec Homebrew, installer vagrant devient facile:

brew update
brew tap phinze/homebrew-cask
brew install brew-cask
brew cask install vagrant

Troisièmement, il n’y a pas de troisièmement

Félicitations! Vagrant est maintenant installé sur votre mac. Vous pouvez le vérifier en faisant:

 $ vagrant --version
Vagrant 1.5.1

Enjoy !

Proxifying play server behind grunt for full stack dev

I like the idea of using the best tool for the job. As I write this the best tool for web frontend development is clearly a js stack. However it is still my belief that the server is better served by a strongly typed language (and I now also prefer statically typed). I currently work on a Play 2.2 application which uses a full js frontend. The problem is that js stacks are better served by grunt (or brunch) with minification, concatenation, sourcemap, coffee compilation, livereload, etc. At the same time play is able to restart and recompile my play app without me needed to do anything.

Getting both to cooperate in dev mode without hitting the cross origin restrictions requires a proxy. Instead of using yet another tool in dev mode to do the proxyfication (I do recommand using such a tool in production though), I decided to have grunt proxify requests he wasn’t able to handle.

Making JDK7 nio FileType detection work on OSX

JDK 7 introduced NIO.2 and the java.nio.file package, within it came the Files featuring a very interesting method : probeContentType(Path path). Mime type detection is always a pain, thus having a simple way to do it in the JDK is a very interesting feature indeed. Unfortunately, on Mac OS X, this feature is broken (see my gist for a test program).

As the javadoc for probeContentType explains, mime type detection is based on having a FileTypeDetector installed. The default one provided in JDK 7 is the GnomeFileTypeDetector class and for some reason it won’t pick up libgio even if it is installed on the system. Or at least, I haven’t managed to get it to detect the lib, if you do I would love to hear from you in the comments. A bug was opened on this subject at Oracle but they decided to fix it only in jdk8 which is not yet released. I tried submitting a new bug report hoping to prompt Oracle to backport the JDK8’s file detector to JDK7. I have little hope, so you can forget about probeContentTypeon OSX, unless …

The FileTypeDetector mechanism uses SPI (Service Provider Interface) to allow for loading additional detection providers. I hacked JDK 8’s default provider and created a small maven project to generate a jar which will register the provider with the JDK. Since this is platform specific issue and some of my coworkers use linux I didn’t add the jar to my project dependencies. Instead I dropped it into my JDK7’s jre/lib/ext folder. This way the jar is registered automatically whenever I use that JDK.

The code can be found on github. Hopefully I have respected the requirements of the JDK licensing by reproducing both the license and the copyright header.

For the impatients, I made a branch with a binary of the jar and a sample mime.types file lifted from some apache source repository and ready to be copied to $HOME/.mime.types.

Bringing Play! 2 Heroku slug size under control

** EDIT 2013-10-11 **

The pull request has been merged. In the discussion, Josh Suereth suggested it should be possible to use the sbt-native-packager which replaced the dist command in play 2.2 to make a better build pack.

** EDIT 2013-08-19 **

I recommend reading up the pull request discussion at github. Basically, if you have a JVM based application, your absolute minimum slug size will be around 77MB because you _must_ package your own JRE in your slug. The default JRE for the stack is not upgraded on a regular basis leaving you exposed to security vulnerabilities.

I had been bothered by my Play! 2 apps slug size before, but never took the time to investigate. I couldn’t understand why sbt dist would yield a 34MB zip while Heroku would end up with a > 100MB archive. While deploying an upgrate to Play! 2.1.3, I noticed it had bloated to 142MB: I had to act.

The current Heroku buildpack uses sbt clean compile stage as its main command instead of sbt dist. I haven’t tried to change that as I wanted something working fast, but I speculate it would be the best way to go for a Play! 2 app.

I cloned the official Heroku buildpack for scala, added some debug output in bin/compile through du -sh ./* and find . \! -type d | xargs ls -Slh to try and understand were the bloat was coming from. To configure a custom buildpack for you app, all you have to do is run the following command :

$ heroku config:set BUILDPACK_URL=

Here is the output from du -sh ./*:

4.0K	./.gitignore
8.0K	./.ivy2
77M		./.jdk
12K		./.profile.d
251M	./.sbt_home
4.0K	./.travis.yml
4.0K	./Procfile
8.0K	./
92K		./app
32K		./conf
55M		./project
1.1M	./public
4.0K	./
44M		./target
56K		./test

My first reaction was : 55MB in project ?! Since I had run a find on the whole directory I was able to check out what was in project, looking only for MB sized artifacts. Here is what I found:

$ grep ./project deploy.log  | grep M
55M	./project
 14M Aug 15 08:19 ./project/boot/scala-2.10.0/lib/scala-compiler.jar
6.8M Aug 15 08:19 ./project/boot/scala-2.10.0/lib/scala-library.jar
3.1M Aug 15 08:19 ./project/boot/scala-2.10.0/lib/scala-reflect.jar
 11M Aug 15 08:19 ./project/boot/scala-2.9.2/lib/scala-compiler.jar
8.5M Aug 15 08:19 ./project/boot/scala-2.9.2/lib/scala-library.jar
1.2M Aug 15 08:19 ./project/boot/scala-2.9.2/org.scala-sbt/sbt/0.12.3/ivy-2.3.0-rc1.jar
2.0M Aug 15 08:19 ./project/boot/scala-2.9.2/org.scala-sbt/sbt/0.12.3/main-0.12.3.jar
1.1M Aug 15 08:23 ./project/target/streams/$global/update/$global/out

Keeping both versions of the scala compiler in the production slug is not really useful. I haven’t tried to check why sbt places this here on Heroku and not on my workstation, but the first thing I added to my buildpack was :

  if [ -d $BUILD_DIR/project/boot ] ; then
    echo "-----> Dropping project boot dir from the slug"
    rm -rf $BUILD_DIR/project/boot  

If you read carefully the output of du above, you will have noted a .jdk folder weighing in at 77MB. That’s right, the default buildpack will leave the JDK in the slug. Remove it since it is only used for compilation:

  if is_play $BUILD_DIR && [ -d $BUILD_DIR/.jdk ] ; then
    echo "-----> Dropping jdk from the slug"
    rm -rf $BUILD_DIR/.jdk

Along the same line, you can drop all the intermediate compilation artifacts with :

  if [ -d $BUILD_DIR/target ] ; then
    echo "-----> Dropping compilation artifacts from the slug"
    rm -rf $BUILD_DIR/target/scala-*
    rm -rf $BUILD_DIR/target/streams
    rm -rf $BUILD_DIR/target/resolution-cache

And now my slug is back to 39MB which is still a bit fat but not so bad. As I said in the introduction, the best would probably be to change the buildpack and use the artifacts generated by sbt dist.

Until the pull request is accepted by the Heroku maintainers, you can fork my version of the build pack. I suggest you don’t use my version directly as I will not maintain my fork after the pull request.