Multi-site support for Gerrit Code Review

Clone this repo:
  1. d039000 Merge branch 'stable-2.16' by David Ostrovsky · 11 days ago master
  2. 0f119a4 Create Dockerised test environment by Fabio Ponciroli · 4 weeks ago
  3. 3a30c78 EventConsumerIT: Assert on event content by David Ostrovsky · 3 weeks ago
  4. a9f97e0 Check for NoteDb migration when loading/testing multi-site by Luca Milanesio · 2 weeks ago
  5. 7df7f3b Add embrional support for split brain detection by Stefano Galarraga · 3 weeks ago

Gerrit multi-site plugin

This plugin allows having multiple Gerrit masters to be deployed across various sites without having to share any storage. The alignment between the masters happens using the replication plugin and an external message broker.

The Gerrit masters requirements are:

  • Gerrit v2.16.5 or later
  • Migrated to NoteDb
  • Connected to the same message broker
  • Accessible behind a load balancer (e.g., HAProxy)

NOTE: The multi-site plugin will not start if Gerrit is not yet migrated to NoteDb.

Currently, the only mode supported is one primary read/write master and multiple read-only masters but eventually the plan is to support N read/write masters. The read/write master is handling any traffic while the read-only masters are serving the Gerrit GUI assets, the HTTP GET REST API and the git-upload-packs. The read-only masters are kept updated to be always ready to become a read/write master.

For more details on the overall multi-site design and roadmap, please refer to the multi-site plugin DESIGN.md document

License

This plugin is released under the same Apache 2.0 license and copyright holders as of the Gerrit Code Review project.

How to build

The multi-site plugin is built like any other Gerrit plugin in tree mode, by cloning Gerrit and the multi-site plugin code, and checking them out on the desired branch.

Example of cloning Gerrit and multi-site for a stable-2.16 build:

git clone -b stable-2.16 https://gerrit.googlesource.com/gerrit
git clone -b stable-2.16 https://gerrit.googlesource.com/plugins/multi-site

cd gerrit/plugins
ln -s ../../multi-site .
rm external_plugin_deps.bzl
ln -s multi-site/external_plugin_deps.bzl .

Example of building the multi-site plugin:

cd gerrit
bazel build plugins/multi-site

The multi-site.jar plugin is generated to bazel-genfiles/plugins/multi-site/multi-site.jar.

Example of testing the multi-site plugin:

cd gerrit
bazel test plugins/multi-site:multi_site_tests

NOTE: The multi-site tests include also the use of Docker containers for instantiating and using a Kafka/Zookeeper broker. Make sure you have a Docker daemon running (/var/run/docker.sock accessible) or a DOCKER_HOST pointing to a Docker server.

How to configure

Install the multi-site plugin into the $GERRIT_SITE/plugins directory of all the Gerrit servers that are part of the multi-site cluster.

Create the $GERRIT_SITE/etc/multi-site.config on all Gerrit servers with the following basic settings:

[kafka]
  bootstrapServers = <kafka-host>:<kafka-port>

[kafka "publisher"]
  enabled = true

[kafka "subscriber"]
  enabled = true

For more details on the configuration settings, please refer to the multi-site configuration documentation.

You need also to setup the Git-level replication between nodes, for more details please refer to the replication plugin documentation.