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  1. Getting started
  2. Dependency management
  3. Code formatting
  4. Workflow
  5. Community

Quick links



Getting started

Thanks for contributing to juju! Contributions like yours make good projects great. Before contributing to juju please read the following sections describing the tools and conventions of this project. This file is a companion to README and it is assumed that file has been read and followed prior.

Specifically, the following commands should already have been run:

$ go get -d -v
$ make install-dependencies

The -d option means the source (for juju and its dependencies) is only downloaded and not built. This is required since the dependencies may be out of sync and fail to build properly. See the Dependency management section for more information.


Juju uses git for source control. To get started, install git and configure your username:

$ git config --global "A. Hacker"
$ git config --global ""

For information on setting up and using git, check out the following:


The upstream juju repository is hosted on Github. Patches to juju are contributed through pull requests (more on that in the Pushing section). So you should have a github account and a fork there. The following steps will help you get that ready:

  1. Sign up for github (a free account is fine):
  2. Add your ssh public key to your account:
  3. Hit the "Fork" button on the web page for the juju repo:

At this point you will have your own copy under your github account. Note that your fork is not automatically kept in sync with the official juju repo (see Staying in sync).

Note that juju has dependencies hosted elsewhere with other version control tools.

Local clone

To contribute to juju you will also need a local clone of your github fork. The earlier go get command will have already cloned the juju repo for you. However, that local copy is still set to pull from and push to the upstream juju github account. Here is how to fix that (replace with your github account name):

$ cd $GOPATH/src/
$ git remote set-url origin<USERNAME>/juju.git

To simplify staying in sync with upstream, give it a "remote" name:

$ git remote add upstream

Add the check script as a git hook:

$ cd $GOPATH/src/
$ ln -s ../../scripts/pre-push.bash .git/hooks/pre-push

This will ensure that any changes you commit locally pass a basic sanity check. Using pre-push requires git 1.8.2 or later, though alternatively running the check as a pre-commit hook also works.

Staying in sync

Make sure your local copy and github fork stay in sync with upstream:

$ cd $GOPATH/src/
$ git pull upstream master
$ git push

Dependency management

In the top-level directory of the juju repo, there is a file, dependencies.tsv, that holds the revision ids of all the external projects that juju depends on. That file is used to freeze the code in external repositories so that juju is insulated from changes to those repos.


godeps is the tool that does the freezing. After getting the juju code, you need to get godeps:

go get

This installs the godeps application. You can then run godeps from the root of juju, to set the revision number on the external repositories:

cd $GOPATH/src/
godeps -u dependencies.tsv

Now you are ready to build, run, test, etc.

Staying up-to-date

The dependencies.tsv file can get out of date, for example when you switch to another branch. When it is out of date, run godeps. In practice, you can wait until you get a compile error about an external package not existing/having an incorrect API, and then rerun godeps.

Updating dependencies

If you update a repo that juju depends on, you will need to recreate dependencies.tsv:

make rebuild-dependencies.tsv

Code formatting

Go already provides a tool, go fmt, that facilitates a standardized format to go source code. The juju project has one additional policy.


Import statements are grouped into 3 sections: standard library, 3rd party libraries, juju imports. The tool "go fmt" can be used to ensure each group is alphabetically sorted. eg:

    import (

        gc ""


Because "" will be referenced frequently in test suites, its name gets a default short name of just "gc".


As a project juju follows a specific workflow:

  1. sync with upstream
  2. create a local feature branch
  3. make desired changes
  4. test the changes
  5. push the feature branch to your github fork
  6. reviews
  7. auto-merge
  8. continuous-integration

Naturally it is not so linear in practice. Each of these is elaborated below.

Sync with upstream

First check that the branch is on master:

$ git branch
* master

Then pull in the latest changes from upstream, assuming you have done the setup as above:

$ git pull upstream master

Feature branches

All development should be done on feature branches based on a current copy of master. So after pulling up your local repo, make a new branch for your work:

$ git checkout -b new_feature


juju uses the gocheck testing framework. gocheck is automatically installed as a dependency of juju. You can read more about gocheck at gocheck is integrated into the source of each package so the standard go test command is used to run gocheck tests. For example

$ go test

will run all the tests in the juju project. By default gocheck prints only minimal output, and as gocheck is hooked into the testing framework via a single go test test per package, the usual go test -v flags are less useful. As a replacement the following commands produce more output from gocheck.

$ go test -gocheck.v

is similar to go test -v and outputs the name of each test as it is run as well as any logging statements. It is important to note that these statements are buffered until the test completes.

$ go test -gocheck.vv

extends the previous example by outputting any logging data immediately, rather than waiting for the test to complete. By default gocheck will run all tests in a package, selected tests can by run by passing -gocheck.f to match a subset of test names.

$ go test -gocheck.f '$REGEX'

Finally, because by default go test runs the tests in the current package, and is not recursive, the following commands are equal, and will produce no output.

$ cd $GOPATH/src/
$ go test
$ go test

Testing and MongoDB

Many tests use a standalone instance of mongod as part of their setup. The mongod binary found in $PATH is executed by these suites.

Some tests (particularly those under ./store/...) assume a MongoDB instance that supports Javascript for map-reduce functions. These functions are not supported by juju-mongodb and the associated tests will fail unless disabled with an environment variable:



When ready for feedback, push your feature branch to github, optionally after collapsing multiple commits into discrete changes:

$ git rebase -i --autosquash master
$ git push origin new_feature

Go to the web page ($YOUR_GITHUB_USERNAME/juju) and hit the "Pull Request" button, selecting master as the target.

This creates a numbered pull request on the github site, where members of the juju project can see and comment on the changes.

Make sure to add a clear description of why and what has been changed, and include the launchpad bug number if one exists.

It is often helpful to mention newly created proposals in the #juju-dev IRC channel on Freenode, especially if you would like a specific developer to be aware of the proposal.

Note that updates to your github project will automatically be reflected in your pull request.

Be sure to have a look at:

Code review

The juju project uses peer review of pull requests prior to merging to facilitate improvements both in code quality and in design. The code review tool is ReviewBoard, hosted at In the event that the site is down, the project will temporarily fall back to github for reviews of critical pull requests.

A review request is automatically created for every pull request. A link to that review request is added to the body of the pull request. Whenever the pull request is updated, the review request is likewise updated. Thus for the normal workflow of contribution, there should be no need to worry about creating or updating review requests.

Once you have created your pull request, it will be reviewed. Make sure to address the feedback. Your request might go through several rounds of feedback before the patch is approved or rejected. Once you get a "ship it" from a member of the juju project, and there are not any "NOT LGTM" comments in ReviewBoard or github, you are ready to have your patch merged by a member of the juju team. Congratulations!

The code review site uses github OAuth for authentication. To log in simply go to login page and click the "github" button. The first time you do this, it will redirect you to github to approve access and then redirect you back. This first time is the only one where you will be redirected to github. Furthermore, ReviewBoard will keep you logged in between visits via session cookies.

That first time you log in, a ReviewBoard account will be created for you using your github username. However, your email address is not added. If you want to receive review-related email, be sure to add your email address to your ReviewBoard profile.

For more information on ReviewBoard see:


Continuous integration

Continuous integration is automated through Jenkins:

The bot runs the test suite after $$merge$$ but before it actually merges the pull request into master.


The juju community is growing and you have a number of options for interacting beyond the workflow and the issue tracker.

Take a look at the community page:

juju has two channels on IRC (

  • #juju
  • #juju-dev

There are also two mailing lists: