|author||Antonio Barone <email@example.com>||Fri Oct 02 18:54:30 2020 +0200|
|committer||Antonio Barone <firstname.lastname@example.org>||Mon Oct 05 11:31:28 2020 +0200|
Ensure All-Users:refs/meta/external-ids doesn't cause split-brains The DESIRED policy was introduced in the early stages of the multi-site to work around locking problems with the global ref-database, which have later been fixed with the introduction of a locking mechanism. Due to the concurrent nature of All-Users:refs/meta/external-ids, the DESIRED policy had been applied by default to avoid causing continuous client failures. The DESIRED policy however, is obsolete and prone to cause spit-brains due to the fact that nothing, really, is done to prevent them: this should not be applied to a crucial core ref such as refs/meta/external-ids. Remove DESIRED policy (that was only used for All-Users:refs/meta/external-ids) and instead make sure that it is REQUIRED to be in sync with the global ref-database.  I5395c22ffdf87fcc3247ea9a5d3afc57df60cfe9 Bug: Issue 13462 Change-Id: I6c8fb571e5467fd5596fb8ee1fcdf0179350a051
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:
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 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.
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
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.
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
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, for more details please refer to the replication plugin documentation.