Hacking MozReview

Want to improve MozReview? This article will help you get started.

Before we begin, let’s introduce the components that make up MozReview.

Review Board
Django-based code-review software.
Mercurial Server
Code reviews are initiated by pushing them to a Mercurial repository.
Review Board actions result in interaction with Bugzilla.
A Review Board extension providing integration with the rest of the MozReview system, including user interface modifications and autoland and Bugzilla support.
A Review Board extension that integrates Review Board with Bugzilla. The code here is slowly being migrated to the mozreview extension, so rbbz should be considered deprecated.
Review Board Mercurial Extension
There exist client-oriented and server-oriented Mercurial extensions to enable Mercurial peers to exchange and interface with review data.

Running a MozReview Instance

It is possible to run a fully isolated, fully local MozReview instance from your machine. This will give you an environment that should behave like production.

You will need to install the dependencies listed here.

You will also need Docker installed. On Linux, this is generally as simple as installing the required package, e.g., on Ubuntu:

$ sudo apt-get install docker.io

You can also install the very latest release directly from Docker.

On Linux, it is necessary to configure Docker to listen on a tcp socket rather than the default configuration, which uses an unix domain socket, in order to get test results which match the expected results. This can be done by editing your configuration file (in /etc/default/docker for Ubuntu 14.04, see the docs for more details) to start docker with the following option:

-H tcp://

You will also need to set the DOCKER_HOST variable:

$ export DOCKER_HOST=

For OS X, you will need to install and start up docker-machine; see the official installation instructions. Make sure you specify more than the default 1024 MB of RAM, which is insufficient for a local MozReview installation, given the number of containers that are created. If you’re using VirtualBox as your driver, this should work (creating a docker machine called “default”):

docker-machine create --driver virtualbox --virtualbox-memory 4096 default

Some MozReview developers have experienced stability problems using Virtualbox and have found that using VMWare as the docker-machine driver results in a better development experience. If you are setting repeated errors from Docker when creating a local environment or running tests, consider switching to VMWare.

Running a local MozReview instance in Windows is not yet supported, but if you get it working, please let us know!

After you have docker up and running, you’ll need to configure your environment. Run the following:

$ ./create-test-environment

This will create a virtualenv in venv/ with all the necessary package dependencies. It will also create Docker images for running Bugzilla. This could take 10-20 minutes to run the first time you run the command (most of the time is spent creating the Bugzilla Docker image).

Now, you can create and start a MozReview instance:

$ ./mozreview start /path/to/instance
waiting for Bugzilla to start
Bugzilla accessible on
Bugzilla URL:
Review Board URL:
Mercurial URL:
Pulse endpoint:
Autoland URL:
Admin username: admin@example.com
Admin password: password
LDAP URI: ldap://
HG Push URL: ssh://

Run the following to use this instance with all future commands:
  export MOZREVIEW_HOME=/Users/gps/tmp/mozreview

Refresh code in the cluster by running:
  ./mozreview refresh

Perform refreshing automatically by running:
  ./mozreview autorefresh

(autorefresh requires `watchman`)

Obtain a shell in a container by running:
  ./mozreview shell <container>

(valid container names include: rbweb, bmoweb, hgrb, autoland)


There is a helper script which will automatically create users, bugs, and a repository, as well as a local clone of the repository that is ready to push:

$ ./start-local-mozreview

This will use ../mozreview-test as the instance path, and locally clone the repository to ../local-mozreview-test-repo.

You should be able to load the printed URLs in your browser and see a working site. If you don’t, file a bug!


Storing MozReview instances inside a Mercurial repository will introduce many untracked files. It is recommended to store your instances outside of a repository checkout.


All mozreview commands take a positional argument defining the path to the instance they should operate on. If you define the MOZREVIEW_HOME environment variable, you do not need to define this argument.

The remainder of this document assumes this environment variable is defined.

Creating Users

There are two primary account systems inside the MozReview cluster: Bugzilla and LDAP.

Bugzilla accounts provide authentication and authorization for web properties, including Bugzilla, MozReview, and Autoland.

LDAP accounts hold information needed to communicate with the Mercurial SSH server. When LDAP accounts are created, an SSH keypair is associated with the account. The public key is added to LDAP so SSH logins may be validated.

The two account systems are completely separate.

Review Board also has its own account system. But it is linked to Bugzilla’s user database and should be thought of an extension rather than a separate account system.

Creating Universal Users

In many scenarios, it is acceptable to create an account in both systems. We call these universal users because they exist everywhere.

The way to do this is with the mozreview create-user command:

$ ./mozreview create-user user1@example.com password 'Example User' \
    --uid 2000 --scm-level 1 --bugzilla-group editbugs

This creates the user1@example.com user with password password and full name Example User. The LDAP account says to use UID 2000 and give the user access level 1. Finally, the user is added to the editbugs Bugzilla group, which gives the user permission to edit bugs.

A SSH keypair for the user is created and configured with LDAP.

Creating LDAP Users

If you would like to create a user in LDAP without a corresponding Bugzilla user (this is rare), you can use the mozreview create-ldap-user command. e.g.:

$ ./mozreview create-ldap-user gszorc@mozilla.com gps 2002 'Gregory Szorc' --key-file ~/.ssh/id_rsa --scm-level 3

Here, we create the account gszorc@mozilla.com with system user name gps with user ID 2 with name Gregory Szorc with an existing RSA SSH keypair and with level 3 source code access.


When specifying an existing key file, the public key will be added to the LDAP server running in the cluster. Your private key remains as a secret on your local machine.

Creating Bugzilla Users

If you would like to create a user in Bugzilla without a corresponding LDAP user, you can use mozreview create-user without the --uid argument. e.g.:

$ ./mozreview create-user me@example.com password 'Joe Smith'

Creating Repositories

MozReview instances are initially empty. They don’t have any repositories you can push to.

To create an empty repository to hold reviews, use mozreview:

$ ./mozreview create-repo repo_name
HTTP URL (read only):
SSH URL (read+write): ssh://

Run the following to create a configured clone:
  ./mozreview clone repo_name /path/to/clone

And a clone bound to a particular user:
  ./mozreview clone repo_name /path/to/clone --user <user>

Pushing to repositories is done via SSH, as this is how production works.

Creating Configured Repository Clones

It is common to want to configure a local repository clone to talk to a review repository from your local MozReview cluster. The mozreview clone command exists to make creating one simple:

$ ./mozreview clone repo_name /path/to/dest

The hgrc of the created repository will be configured such that the repository is bound to the MozReview instance it came from.

Passing the --user argument to the clone command will further bind the repository to a specific user. When used, hg push commands will automatically use the appropriate SSH key and username.

Configuring a Hosting Service for a Repository

Using Autoland functionality from within MozReview requires configuring a hosting service for your test repository. The hosting service contains the try repository URL, the landing repository URL

You will need to login as the admin user in your reviewboard instance. To avoid the bugzilla login, visit /admin in your browser. Once logged in, click on Repositories and then the name of your repo, e.g. test-repo. Copy the current URL and then click on Hosting Service and select the hmo hosting service.

Enter a username for the hosting service, paste the URL to the repository in the Repository URL field. Enter try into the Try Repository URL field will work for local testing with Autoland.

You should end up with something like the following:


Refreshing Code

Because processes are running inside Docker containers and are operating on copies of code, changes to the source code in your working directory will not automatically take effect in running processes.

To refresh code running on the cluster, run the refresh sub-command:

$ ./mozreview refresh

The autorefresh command can be used to start a file watching daemon that will automatically refresh the cluster when local files are changed:

$ ./mozreview autorefresh


Use of autorefresh is highly recommended when doing development, as it will save you the overhead of having to manually type a refresh command every time you change something.

Stopping the Servers

When you run mozreview start, a number of Docker containers and daemon processes will be started. These will linger forever - taking up system resources - until there is some form of intervention.

The easiest way to stop everything related to the running MozReview instance is to run mozreview stop. e.g.:

$ ./mozreview stop

Exporting Environment Variables

Many support tools (bugzilla, reviewboard, etc) look for magic environment variables to configure things like what server to talk to.

The shellinit sub-command can be used to mass export all variables defining how a MozReview cluster works:

$ $(./mozreview shellinit)

Interacting with Bugzilla

The bugzilla tool in the root of the repository provides a quick an convenient interface to performing common Bugzilla operations, such as creating bugs and printing the state of bugs.

This tool has the dual role of supporting both machines and humans. The tests rely heavily on this tool to perform small, well-defined Bugzilla interactions. You are encouraged to use the tool to help you hack on MozReview.

Since the tool had its origins in testing land, it currently requires environment variable(s) to define which Bugzilla instance to use.

If you have the MOZREVIEW_HOME variable set, the Bugzilla instance associated with that MozReview instance is used. Else, you will need to define the following variables:

This must be set the base URL of the Bugzilla instance you wish to communicate with.
The username your API requests to Bugzilla will use.
The password your API requests to Bugzilla will use.

Interacting with Review Board

The reviewboard tool in the root of the repository provides a mechanism to perform well-defined interactions with Review Board instances. You are encouraged to use the tool to help you hack on MozReview.

The tool had its origins in testing code, so its human interface could use some love.

You’ll need to define your Review Board credentials through environment variables: BUGZILLA_USERNAME and BUGZILLA_PASSWORD. The name bugzilla is in there because MozReview shares its user database with Bugzilla.

Code Locations

pylib/rbbz contains the modifications to Review Board to enable Bugzilla integration and support for series of reviews.

pylib/mozreview contains the UI modifications to Review Board.

hgext/reviewboard contains the client and server Mercurial extensions.

pylib/reviewboardmods contains the server-side code that runs as part of pushing reviews to the Mercurial server. This contains the low-level code that maps commits to review requests and ensures Review Board review state is in a sane state. This code is logically part of the Mercurial server extension. However, it exists in its own directory so it can eventually be leveraged by Git and so it has a license that isn’t the GPL (Review Board isn’t GPL - Mercurial is).

pylib/mozhg contains some Mercurial support APIs used by the Mercurial integration. This includes code for finding Bugzilla credentials.

Review Board Modifications

Review Request Extra Data

We store the following in the extra_data field of review requests:


String with value True.

The presence of this property differentiates review requests created by MozReview’s special commit tracking code from ones created by vanilla Review Board. Many of our customizations to Review Board ignore review requests unless they have this annotation.


String with values True or False.

This property identifies whether this review request is a special parent/squashed/tracking review request.

Since Review Board doesn’t yet have the concept of multiple commits per review request, we needed to invent one. This property helps us distinguish the parent/tracking review request from its children.


String with user-supplied value.

The value of this string groups multiple review requests belonging to the same logical review together. This property is defined on all our review requests and it should be the same for every review request tracked by a single squashed/parent review request.


String of JSON serialization of an array of strings corresponding to review request IDs.

This is set on parent review requests only.

This array holds the list of review requests currently associated with this review request series.


String of JSON serialization of an array of strings corresponding to review request IDs.

This is set on parent review requests only.

When drafts are created, sometimes extra review requests get created and associated with the parent review request but never actually get published (say you upload a commit by accident and then decide to remove it from review). There is no way to delete and recycle a review request, even if it has never been published. Instead, we track which review requests would become orphans. At publish time, we discard the drafts and review requests.


String of JSON serialization of an array of strings corresponding to review request IDs.

This is set on parent review requests only.

The list of review requests in this property tracks which review requests tracked by this parent review request should be published when the parent review request moves from draft to published state.

String SHA-1 of the commit currently associated with this review request.

Running Tests

The MozReview tests are all defined as part of the Mercurial extension. To run the tests:

$ ./run-tests hgext/reviewboard/tests/ autoland/tests/

There are also some Selenium-based tests. You’ll need Firefox (release) installed to run them:

$ ./run-tests pylib/mozreview/mozreview/tests/

Filing Bugs

Found a bug in MozReview or want to create a bug to track an improvement? File bugs against MozReview :: General at https://bugzilla.mozilla.org/enter_bug.cgi?product=MozReview&component=Testing%20%2F%20Development%20Environment.


General discussion on MozReview development and direction occurs on the mozilla.dev.version-control group, which is available via mailing list, Google Group, or NNTP.

Submitting Changes

See Contributing for how to formulate and submit changes for the version-control-tools repository.