BUCK Is My New Friend

January 26, 2016

Happy belated New Year everybody! New year, new resolutions, new thing. There were a lot of things I want to write this year and for my first article is about my passion: software build. I’ve spent my last few years optimising developer productivity, and one most important thing that takes a lot of precious developer time, other than loading the over-bloated IDE and ever-slow emulator/simulator is compiling. To increase the productivity, we need to minimise and fasten the feedback loop. After ditching the whole IDE my next target is to find a faster build system than Gradle, and luckily I found one, and it’s called buck, and it is amazing.


Let’s start with some knowledge about buck. According to their site:

Buck logo according to their site.

Buck is a build system developed and used by Facebook. It encourages the creation of small, reusable modules consisting of code and resources, and supports a variety of languages on many platforms.

At first, I just don’t care abouth what is written in the bold above. My goal was to eliminate time between builds, and it delivers it pretty well. I used it to compile my very basic RxSample project and compare it with Gradle.

The Comparison Benchmark

I created a simple test using my Macbook Pro (SSD with 16 GB RAM) with these prerequisites to make the build is consistently reproducible:

  1. All dependencies already been fetched.
  2. Startup time is counted as well as the execution time.
  3. Test again on rebuilding with minor changes on the .java file.
% time ./gradlew assembleDebug 

And now with buck:

% time buck build //...

The result is shown here:

Gradle vs Buck

As you can see, it’s clear, that Buck wins on all facets. This comparison is very raw as it’s only one project. Buck excels on a project composed from multiple modules as each modules will be built in parallel.

Setting Up Your Project For Buck

Buck is created by encouraging the creation of modules in mind. While gradle is project-based, buck is very simple file-based build tool. Unfortunately, the IDE support for buck is far from perfect. To make the developers who use IDE happy, we could just add buck to our project.

The first step to create a buck project is to make a .buckconfig file in the project root. When buck find this file it considers the directory as the project root, and can be referred as //. The .buckconfig file is an INI file with entries are documented in the documentation.


;Setting for Android Build Tools and Target
build_tools_version = 23.0.2
target = Google Inc.:Google APIs:21

;Maven Repositories, where we will fetch the dependencies
;We only use jcenter
jcenter = https://jcenter.bintray.com/

Buck has the concept of Build Rule, Build Target, and Build File. In short, Build File is a file named BUCK that placed in the directory that contains Build Rule to make the Build Target. According to buck documentation, we can only refer source files in “nearest” build file or closest direct ancestor in our projet file tree. For more information, please refer to buck documentation.

To make life simpler, we actually only have one BUCK file in the same directory as the build.gradle file, in the app directory listing several build rules to generate the resulting APK file. Let’s do the dance:

% touch app/BUCK && vi app/BUCK

Adding Dependencies

Buck actually does not care about our external dependencies as well as the transitive dependencies. It declares itself a build tool, not a dependency tool. We can refer the external maven depencies using mvn url parser on remote_file build rule and then use android_prebuilt_aar and prebuilt_jar to make the file is able to be referenced as dependencies.

# RxAndroid
  name = "rxandroid-aar",
  url  = "mvn:io.reactivex:rxandroid:aar:1.0.1",
  sha1 = "563323d4f90cdb87d067fcf02b06c5d16bb1a258"

  name = "rxandroid",
  aar  = ":rxandroid-aar" # Refer by project name references

# RxJava
  name = "rxjava-jar",
  url  = "mvn:io.reactivex:rxjava:jar:1.0.14",
  sha1 = "898f9ab61e2a23afd615f0b0389478bec86f49f9"

  name = "rxjava",
  binary_jar = ":rxjava-jar"

# RxBinding
  name = "rxbinding-aar",
  url  = "mvn:com.jakewharton.rxbinding:aar:0.2.0",
  sha1 = "97c550ecaf825c003b1b30cb1b754745fa79307a"

  name = "rxbinding",
  aar  = :rxbinding-aar"

# Android Support annotations
  name = "support-annotations-jar",
  url  = "mvn:com.android.support:support-annotations:jar:23.1.1",
  sha1 = "8d680ba5a623724d1fb0e81c36a790f023a6cede"

Buck’s build rules are Python functions. From the example above, remote_file(), android_prebuilt_aar(), and prebuilt_jar() are the build rules. Facebook decided buck built-in build rules with “do one thing” mentality. The remote_file() build rule like above is only to fetch arbitrary file from somewhere.

In contrast with gradle which will reads the maven’s pom to decide the transitive dependencies, buck is relatively dumb. It only cares fetching files and matching the SHA1. If you have transitive dependencies you’d need to specify them one-by-one explicitely as shown by rxandroid which depends on rxjava above. The version is also need to be very specific. We cannot use dynamic version. This is to make sure that the build is reproducible.

Because remote_file is only for fetching arbitrary file and do not know the type of the file, the android_prebuilt_aar() and prebuilt_jar() refer to the file downloaded by remote_file and says that file need to be treated as aar or jar. Referring other build rule name can be done by prefixing it with colon :. We’re finished adding deps to our projects.

Building the Application

To create an application, we need to create a Debug Keystore. I usually avoid checked in any keystore to the source code. If your developers are working with Android Studio, most of the time it’s saved in default location, in OSX and Linux, it is in ~/.android/debug.keystore. So we need to copy them locally.

  name = "debug-keystore",
  deps = [":debug-keystore-file"],
  store = "debug.keystore",
  properties = debug.properties,

You can see that we need to create a properties file. This file contains username and password for debug files. So let’s create a property file:

key.alias = androiddebugkey
key.store.password = android
key.alias.password = android

Try to execute buck build //app/... and see if creates error. With this we’re ready to create our APK. But before that, let’s see what is actually inside an APK:

  1. A dex-ed classes.dex coming from classes.jar.
  2. Resources.
  3. Manifest.

Buck is very explicit. To create an APK we need output from android_library() with sources and android_resources(). So let’s define the resources

  name = "res",
  res  = "src/main/res",
  package = "com.ykode.rxsample"

This rule will package the resources and generate R.java. So we then create an android_library rule containing all classes and output from resources.

  name = "app-lib",
  srcs = glob["src/main/java/**/*.java"],
  deps = [

It lists all references to dependencies that we’ve been declared before in th deps parameter. We also add :res as one of the deps because we need to refer the R.java implicitly generated from previous step.

Now we have complete ingredients, let’s create the APK using android_binary() build rule:

  name = "apk-debug",
  manifest = "src/main/AndroidManifest.xml",
  keystore = ":debug-keystore",
  package_type = "debug",
  deps = [":res", ":app-lib"]

This will generate APK and placed in the buck-out/gen directory.

Running on device or simulator

If you want to run on device or simulator, first we need to run the emulator. If you are not using IDE, we can use nohup command to invoke the emulator to avoid closing when the terminal emulator exists.

% nohup emulator -avd <avd_name> > /dev/null 2>&1 &

This will run emulator for avd. To get the name of each avd use android list avd command. And then we can run the app by using this buck command.

% buck install --run //app:apk-debug

And voila, your app is installed and running. You can change some files and then run the command again. In my case, the process took less than 2 seconds for each rebuild and installation.

Build Run


Buck is very promising build tool. While the first setup is not as easy as gradle, the speed improvement worth it as it reduce the development time significantly by make feedback loop a lot faster and unit test and integration testing loaded faster.

I intend to write more specifically about why buck actually enforces you to make modular module and how I accomplishes it. So, stay tuned.

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BUCK Is My New Friend - January 26, 2016 - Didiet Noor