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.
Supports multiple read/write masters across multiple sites across different geographic locations. The Gerrit nodes are kept synchronized between each other using the replication plugin and a global ref-database in order to detect and prevent split-brains.
For more details on the overall multi-site design and roadmap, please refer to the multi-site plugin DESIGN.md document
This plugin is released under the same Apache 2.0 license and copyright holders as of the Gerrit Code Review project.
The multi-site plugin can only be built in tree mode, by cloning Gerrit and the multi-site plugin code, and checking them out on the desired branch.
To build the multi-site plugin in addition to the gerrit core plugins also the following plugins need to be present in the plugins directory:
- pull-replication
- healthcheck
- events-broker
- global-refdb
Example of cloning Gerrit, the multi-site plugin and the plugins it depends on for a stable-3.11 build:
git clone --recurse-submodules -b stable-3.11 https://gerrit.googlesource.com/gerrit
git clone -b stable-3.11 https://gerrit.googlesource.com/plugins/multi-site
git clone -b stable-3.11 https://gerrit.googlesource.com/modules/events-broker
git clone -b stable-3.11 https://gerrit.googlesource.com/modules/global-refdb
git clone -b stable-3.11 https://gerrit.googlesource.com/plugins/healthcheck
git clone -b stable-3.11 https://gerrit.googlesource.com/plugins/pull-replication
cd gerrit/plugins
ln -s ../../multi-site .
ln -s ../../events-broker .
ln -s ../../global-refdb .
ln -s ../../healthcheck .
ln -s ../../pull-replication .
Example of building the multi-site plugin:
cd gerrit
bazelisk 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
bazelisk test plugins/multi-site/...
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. In addition docker-compose needs to be installed.
Each Gerrit server of the cluster must be identified with a globally unique
instance-id
defined in $GERRIT_SITE/etc/gerrit.config.
When migrating from a multi-site configuration with Gerrit v3.3 or earlier,
you must reuse the instance-id value stored under $GERRIT_SITE/data/multi-site.
Example:
[gerrit]
instanceId = 758fe5b7-1869-46e6-942a-3ae0ae7e3bd2
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:
[gerrit]
installDbModule = com.googlesource.gerrit.plugins.multisite.GitModule
installModule = com.googlesource.gerrit.plugins.multisite.Module
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. This can be done with either pull or push replication plugin.
For information about available HTTP endpoints please refer to the documentation.
