# Gerrit Code Review - Building with Buck

version v2.11.4-22-ge0c0f29

## Installation

Note that you need to use Java 7 for building gerrit.

There is currently no binary distribution of Buck, so it has to be manually built and installed. Apache Ant is required. Currently only Linux and Mac OS are supported. Buck requires Python version 2.7 to be installed.

Clone the git and build it:

      git clone https://github.com/facebook/buck
      cd buck
      git checkout $(cat ../gerrit/.buckversion)
      ant

If you don’t have a `bin/` directory in your home directory, create one:

      mkdir ~/bin

Add the `~/bin` folder to the path:

      PATH=~/bin:$PATH

Note that the buck executable needs to be available in all shell sessions, so also make sure it is appended to the path globally.

Add a symbolic link in `~/bin` to the buck and buckd executables:

      ln -s `pwd`/bin/buck ~/bin/
      ln -s `pwd`/bin/buckd ~/bin/

Verify that `buck` is accessible:

      which buck

To enable autocompletion of buck commands, install the autocompletion script from `./scripts/buck_completion.bash` in the buck project. Refer to the script’s header comments for installation instructions.

## Eclipse Integration

### Generating the Eclipse Project

Create the Eclipse project:

      tools/eclipse/project.py

In Eclipse, choose 'Import existing project' and select the `gerrit` project from the current working directory.

Expand the `gerrit` project, right-click on the `buck-out` folder, select 'Properties', and then under 'Attributes' check 'Derived'.

Note that if you make any changes in the project configuration that get saved to the `.project` file, for example adding Resource Filters on a folder, they will be overwritten the next time you run `tools/eclipse/project.py`.

### Refreshing the Classpath

If an updated classpath is needed, the Eclipse project can be refreshed and missing dependency JARs can be downloaded:

      tools/eclipse/project.py

### Attaching Sources

To save time and bandwidth source JARs are only downloaded by the buck build where necessary to compile Java source into JavaScript using the GWT compiler. Additional sources may be obtained, allowing Eclipse to show documentation or dive into the implementation of a library JAR:

      tools/eclipse/project.py --src

## Building on the Command Line

### Gerrit Development WAR File

To build the Gerrit web application:

      buck build gerrit

The output executable WAR will be placed in:

      buck-out/gen/gerrit.war

### Extension and Plugin API JAR Files

To build the extension, plugin and GWT API JAR files:

      buck build api

Java binaries, Java sources and Java docs are generated into corresponding project directories in `buck-out/gen`, here as example for plugin API:

      buck-out/gen/gerrit-plugin-api/plugin-api.jar
      buck-out/gen/gerrit-plugin-api/plugin-api-src.jar
      buck-out/gen/gerrit-plugin-api/plugin-api-javadoc.jar

Install {extension,plugin,gwt}-api to the local maven repository:

      buck build api_install

Install gerrit.war to the local maven repository:

      buck build war_install

### Plugins

To build all core plugins:

      buck build plugins:core

The output JAR files for individual plugins will be placed in:

      buck-out/gen/plugins/<name>/<name>.jar

The JAR files will also be packaged in:

      buck-out/gen/plugins/core.zip

To build a specific plugin:

      buck build plugins/<name>:<name>

The output JAR file will be be placed in:

      buck-out/gen/plugins/<name>/<name>.jar

Note that when building an individual plugin, the `core.zip` package is not regenerated.

Additional plugins with BUCK files can be added to the build environment by cloning the source repository into the plugins subdirectory:

      git clone https://gerrit.googlesource.com/plugins/<name> plugins/<name>
      echo /plugins/<name> >>.git/info/exclude

Additional plugin sources will be automatically added to Eclipse the next time project.py is run:

      tools/eclipse/project.py

### Documentation

To build only the documentation for testing or static hosting:

      buck build docs

The generated html files will NOT come with the search box, and will be placed in:

      buck-out/gen/Documentation/searchfree__tmp/Documentation

The html files will also be bundled into `searchfree.zip` in this location:

      buck-out/gen/Documentation/searchfree.zip

To build the executable WAR with the documentation included:

      buck build withdocs

The WAR file will be placed in:

      buck-out/gen/withdocs.war

### GWT Compile Report

The GWT compiler can output a compile report (or "story of your compile"), describing the size of the JavaScript and which source classes contributed to the overall download size.

      buck build soyc

The report will be written as an HTML page to the extras directory, and can be opened and viewed in any web browser:

      extras/gerrit_ui/soycReport/compile-report/index.html

Only the "Split Point Report" is created, "Compiler Metrics" are not output.

### Gerrit Release WAR File

To build the release of the Gerrit web application, including documentation and all core plugins:

      buck build release

The output release WAR will be placed in:

      buck-out/gen/release.war

### Combined build target

To build release and api targets, a combined build target is provided:

      buck build all

## Running Unit Tests

To run all tests including acceptance tests:

      buck test

To exclude slow tests:

      buck test --all --exclude slow

To include a specific group of acceptance tests:

      buck test --all --include api

The following groups of tests are currently supported:

- api

- edit

- git

- pgm

- rest

- server

- ssh

To run a specific test, e.g. the acceptance test `com.google.gerrit.acceptance.git.HttpPushForReviewIT`:

      buck test //gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/git:HttpPushForReviewIT

To create test coverage report:

      buck test --code-coverage --code-coverage-format html --no-results-cache

The HTML report is created in `buck-out/gen/jacoco/code-coverage/index.html`.

## Dependencies

Dependency JARs are normally downloaded automatically, but Buck can inspect its graph and download any missing JAR files. This is useful to enable subsequent builds to run without network access:

      tools/download_all.py

When downloading from behind a proxy (which is common in some corporate environments), it might be necessary to explicitly specify the proxy that is then used by `curl`:

      export http_proxy=http://<proxy_user_id>:<proxy_password>@<proxy_server>:<proxy_port>

Redirection to local mirrors of Maven Central and the Gerrit storage bucket is supported by defining specific properties in `local.properties`, a file that is not tracked by Git:

      echo download.GERRIT = http://nexus.my-company.com/ >>local.properties
      echo download.MAVEN_CENTRAL = http://nexus.my-company.com/ >>local.properties

The `local.properties` file may be placed in the root of the gerrit repository being built, or in `~/.gerritcodereview/`. The file in the root of the gerrit repository has precedence.

## Building against unpublished Maven JARs

To build against unpublished Maven JARs, like gwtorm or PrologCafe, the custom JARs must be installed in the local Maven repository (`mvn clean install`) and `maven_jar()` must be updated to point to the `MAVEN_LOCAL` Maven repository for that artifact:

     maven_jar(
       name = 'gwtorm',
       id = 'gwtorm:gwtorm:42',
       license = 'Apache2.0',
       repository = MAVEN_LOCAL,
     )

## Building against unpublished JARs, that change frequently

If a dependent Gerrit library is undergoing active development it must be recompiled and the change must be reflected in the Buck build process. For example testing Gerrit against changed JGit snapshot version. After building JGit library, the artifacts are created in local Maven build directory, e. g.:

      mvn package
      /home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT.jar
      /home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT-sources.jar

If as usual, installation of the build artifacts takes place in local maven repository, then the Buck build must fetch them from there with normal `download_file.py` process. Disadvantage of this approach is that Buck cache invalidation must occur to refresh the artifacts after next change-compile-install round trip.

To shorten that workflow and take the installation of the artifacts to the local Maven repository and fetching it again from there out of the picture, `local_jar()` method is used instead of `maven_jar()`:

     local_jar(
       name = 'jgit',
       jar = '/home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT.jar',
       src = '/home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT-sources.jar',
       deps = [':ewah']
     )

This creates a symlink to the Buck targets direct against artifacts in another project’s Maven target directory:

      buck-out/gen/lib/jgit/jgit.jar ->
      /home/<user>/projects/jgit/org.eclipse.jgit/target/org.eclipse.jgit-3.3.0-SNAPSHOT.jar

After `buck clean` and `buck build lib/jgit:jgit` the symbolic link that was created the first time is lost due to Buck’s caching mechanism. This means that when a new version of the local artifact is deployed (by running `mvn package` in the JGit project in the example above), Buck is not aware of it, because it still has a stale version of it in its cache.

To solve this problem and re-create the symbolic link, you don’t need to wipe out the entire Buck cache. Just rebuilding the target with the `--no-cache` option does the job:

      buck clean
      buck build --no-cache lib/jgit:jgit

## Building against artifacts from custom Maven repositories

To build against custom Maven repositories, two modes of operations are supported: with rewrite in local.properties and without.

Without rewrite the URL of custom Maven repository can be directly passed to the maven_jar() function:

      GERRIT_FORGE = 'http://gerritforge.com/snapshot'

      maven_jar(
        name = 'gitblit',
        id = 'com.gitblit:gitblit:1.4.0',
        sha1 = '1b130dbf5578ace37507430a4a523f6594bf34fa',
        license = 'Apache2.0',
        repository = GERRIT_FORGE,
     )

When the custom URL has to be rewritten, then the same logic as with Gerrit known Maven repository is used: Repo name must be defined that matches an entry in local.properties file:

      download.GERRIT_FORGE = http://my.company.mirror/gerrit-forge

And corresponding BUCK excerpt:

      GERRIT_FORGE = 'GERRIT_FORGE:'

      maven_jar(
        name = 'gitblit',
        id = 'com.gitblit:gitblit:1.4.0',
        sha1 = '1b130dbf5578ace37507430a4a523f6594bf34fa',
        license = 'Apache2.0',
        repository = GERRIT_FORGE,
     )

### Caching Build Results

Build results can be locally cached, saving rebuild time when switching between Git branches. Buck’s documentation covers caching in buckconfig. The trivial case using a local directory is:

      cat >.buckconfig.local <<EOF
      [cache]
        mode = dir
        dir = buck-cache
      EOF

### Cleaning The Buck Cache

The cache for the Gerrit Code Review project is located in `~/.gerritcodereview/buck-cache/cache`.

The Buck cache should never need to be manually deleted. If you find yourself deleting the Buck cache regularly, then it is likely that there is something wrong with your environment or your workflow.

If you really do need to clean the cache manually, then:

     rm -rf ~/.gerritcodereview/buck-cache/cache

Note that the root `buck-cache` folder should not be deleted as this is where downloaded artifacts are stored.

### Using Buck daemon

Buck ships with a daemon command `buckd`, which uses the Nailgun protocol for running Java programs from the command line without incurring the JVM startup overhead.

Using a Buck daemon can save significant amounts of time as it avoids the overhead of starting a Java virtual machine, loading the buck class files and parsing the build files for each command.

It is safe to run several buck daemons started from different project directories and they will not interfere with each other. Buck’s documentation covers daemon in buckd.

To use `buckd` the additional watchman program must be installed.

To disable `buckd`, the environment variable `NO_BUCKD` must be set. It’s not recommended to put it in the shell config, as it can be forgotten about it and then assumed Buck was working as it should when it should be using buckd. Prepend the variable to Buck invocation instead:

      NO_BUCKD=1 buck build gerrit

### Installing watchman

Watchman is used internally by Buck to monitor directory trees and is needed for buck daemon to work properly. Because buckd is activated by default in the latest version of Buck, it searches for the watchman executable in the path and issues a warning when it is not found and kills buckd.

To prepare watchman installation on Linux:

      git clone https://github.com/facebook/watchman.git
      cd watchman
      ./autogen.sh

To install it in user home directory (without root privileges):

      ./configure --prefix $HOME/watchman
      make install

To install it system wide:

      ./configure
      make
      sudo make install

Put $HOME/watchman/bin/watchman in path or link to $HOME/bin/watchman.

To install watchman on OS X:

      brew install --HEAD watchman

See the original documentation for more information: Watchman installation.

### Override Buck’s settings

Additional JVM args for Buck can be set in `.buckjavaargs` in the project root directory. For example to override Buck’s default 1GB heap size:

      cat > .buckjavaargs <<EOF
      -XX:MaxPermSize=512m -Xms8000m -Xmx16000m
      EOF

## Rerun unit tests

Test execution results are cached by Buck. If a test that was already run needs to be repeated, the unit test cache for that test must be removed first:

      rm -rf buck-out/bin/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/group/.AddRemoveGroupMembersIT/

After clearing the cache, the test can be run again:

      buck test //gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/group:AddRemoveGroupMembersIT
      TESTING //gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/group:AddRemoveGroupMembersIT
      PASS  14,9s  8 Passed   0 Failed   com.google.gerrit.acceptance.rest.group.AddRemoveGroupMembersIT
      TESTS PASSED

An alternative approach is to use Buck’s `--filters` (`-f`) option:

      buck test -f 'com.google.gerrit.acceptance.rest.change.SubmitByMergeAlwaysIT'
      TESTING SELECTED TESTS
      PASS  14,5s  6 Passed   0 Failed   com.google.gerrit.acceptance.rest.change.SubmitByMergeAlwaysIT
      TESTS PASSED

When this option is used, the cache is disabled per design and doesn’t need to be explicitly deleted.

Note that when this option is used, the whole unit test cache is dropped, so repeating the

    buck test

causes all tests to be executed again.

To run tests without using cached results at all, use the `--no-results-cache` option:

    buck test --no-results-cache

## Troubleshooting Buck

In some cases problems with Buck itself need to be investigated. See for example this attempt to upgrade Buck and the fix that was needed to make the update possible.

To build Gerrit with a custom version of Buck, the following steps are necessary:

1. In the Buck git apply any necessary changes from pull requests

2. Compile Buck with `ant`

3. In the root of the Gerrit project create a `.nobuckcheck` file to prevent Buck from updating itself

4. Replace the sha1 in Gerrit’s `.buckversion` file with the required version from the custom Buck build

5. Build Gerrit as usual

Part of Gerrit Code Review