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title: "Gerrit's History"
permalink: about.html
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## Google Mondrian

Google developed [Mondrian], a Perforce based code review tool to
facilitate peer-review of changes prior to submission to the central
code repository.  Mondrian is not open-source, as it is tied to the
use of [Perforce] and to many Google-only services, such as
[Bigtable].  Google employees have often described how useful Mondrian
and its peer-review process is to their day-to-day work.

[Mondrian]: https://www.youtube.com/watch?v=sMql3Di4Kgc
[Perforce]: http://www.perforce.com/
[Bigtable]: http://research.google.com/archive/bigtable.html
[Rietveld]: https://github.com/rietveld-codereview/rietveld

## Rietveld

Guido van Rossum open-sourced portions of Mondrian within [Rietveld],
a similar code review tool running on Google App Engine, but for use
with Subversion rather than Perforce.  Rietveld is in common use by
many open-source projects, facilitating their peer reviews much as
Mondrian does for Google employees.  Unlike Mondrian and the Google
Perforce triggers, Rietveld is strictly advisory and does not enforce
peer-review prior to submission.

## Gitolite

Git is a distributed version control system, wherein each repository
is assumed to be owned/maintained by a single user.  There are no
inherent security controls built into Git, so the ability to read from
or write to a repository is controlled entirely by the host's
filesystem access controls.  When multiple maintainers collaborate on
a single shared repository a high degree of trust is required, as any
collaborator with write access can alter the repository.

[Gitolite] provide tools to secure centralized Git
repositories, permitting multiple maintainers to manage the same
project at once, by restricting the access to only over a secure
network protocol, much like Perforce secures a repository by only
permitting access over its network port.

[Gitolite]: http://gitolite.com/gitolite/index.html

## Android

The [Android Open Source Project][AOSP] (AOSP) was founded by Google
by the open-source releasing of the Android operating system.  AOSP
has selected Git as its primary version control tool.  As many of the
engineers have a background of working with Mondrian at Google, there
is a strong desire to have the same (or better) feature set available
for Git and AOSP.

[AOSP]: http://source.android.com/

## The Rietveld fork

Gerrit Code Review started as a simple set of patches to Rietveld, and
was originally built to service AOSP. This quickly turned into a fork
as Rietveld was a technology demo of the AppEngine platform, and
access control features would complicate the Rietveld code base. As
the functionality and code were starting to become drastically
different, a different name was needed. Gerrit calls back to the
original namesake of Rietveld, [Gerrit
Rietveld](http://en.wikipedia.org/wiki/Gerrit_Rietveld), a Dutch
architect.

## Gerrit 2.x rewrite

Gerrit 2.x is a complete rewrite of the Gerrit fork, changing the
implementation from Python on Google App Engine, to Java on a J2EE
servlet container and a SQL database.


## Gerrit 3.x rewrite

Since Gerrit 3.x
[NoteDb](https://gerrit-review.googlesource.com/Documentation/note-db.html)
replaced the SQL database and all metadata is now stored in Git. The
user interface migrated away from GWT to Polymer.