Merge branch 'stable-3.0'

* stable-3.0:
  Move routers configuration out of kafka domain
  Move subscribers related code out of kafka module
  Use BrokerApi for events consuming
  Move SourceAwareEventWrapper out of the kafka package
  Move Kafka consumer logic to a separate class
  Split event consumer logic into separate steps
  Move broker publish metrics to the BrokerApiWrapper
  Introduce DynamicItem<BrokerApi> and its BrokerApiWrapper
  Move BrokerPublisher into the Kafka package domain
  Rename EventFamily to EventTopic
  Use BrokerApi for sending stream events
  Use BrokerApi for sending project list updates
  Use BrokerApi for sending index events
  Introduce the abstract BrokerApi
  Message subscriber metric for number of message consumed
  Skip message logging when publishing failed
  ForwardedIndexChangeHandler: Suppress FutureReturnValueIgnored warning

Leverage the MultiSiteMetrics hierarchy in SubscriberMetrics for
making easier to create new metrics.

Change-Id: Icb1531ad958fed1b9a4e9396ad5d4d7379c8d0f6
tree: af258019f9ddd258778dec018f38d234789ab0da
  1. .bazelrc
  2. .gitignore
  3. .mailmap
  4. .settings/
  5. BUILD
  10. bazlets.bzl
  11. docker-compose.kafka-broker.yaml
  12. dockerised_local_env/
  13. external_plugin_deps.bzl
  14. images/
  15. setup_local_env/
  16. src/
  17. tools/

Gerrit multi-site plugin

This plugin allows to deploy a distributed cluster of multiple Gerrit masters each using a separate site without sharing any storage. The alignment between the masters happens using the replication plugin and an external message broker.

Requirements for the Gerrit masters are:

  • Gerrit v2.16.5 or later
  • Migrated to NoteDb
  • Connected to the same message broker
  • Accessible via 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 multiple 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 git fetch requests (git-upload-pack). The read-only masters are kept synchronized with the read/write master in order 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 document


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
git clone -b stable-2.16

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-bin/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/lib directory of all the Gerrit servers that are part of the multi-site cluster. Create a symbolic link from $GERRIT_SITE/lib/multi-site.jar into the $GERRIT_SITE/plugins.

Add the multi-site module to $GERRIT_SITE/etc/gerrit.config as follows:

  installDbModule = com.googlesource.gerrit.plugins.multisite.GitModule
  installModule = com.googlesource.gerrit.plugins.multisite.Module

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

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

[kafka "publisher"]
  enabled = true

[kafka "subscriber"]
  enabled = true

  enabled = true

[ref-database "zookeeper"]
  connectString = "localhost:2181"

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

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