We use Gerrit for our code review system for Git. It supersedes the CodeReview MediaWiki extension we have used for Subversion.
Monitoring dashboards: https://grafana.wikimedia.org/dashboards/f/5AnaHr2Mk/gerrit
- Built-in Gerrit documentation
- Gerrit test install, hosted in devtools Cloud VPS project
- Commit message guidelines
- Gerrit JavaMelody Monitoring
- Gerrit test instance
Gerrit is installed on gerrit1001 in the prefix /var/lib/gerrit2 and serves public request at https://gerrit.wikimedia.org/r/) . A replica runs at gerrit2001 which serves requests at https://gerrit-replica.wikimedia.org/r/ ), it is intended for a switch over and for various bots in order to offload the primary instance.
Gerrit is a Java daemon which listens for HTTP connections (port 8080) and SSH connections (port 29418). Apache proxies the relevant URLs on port 80 and 443 through to Gerrit. The SSH port provides a restricted shell for Git checkouts and administrative commands.
Since the Gerrit v3.2 upgrade in summer 2020, Gerrit no longer uses a conventional, relational database. So if you read somewhere about Gerrit's MySQL (or similar) database or "reviewdb", it's stale information. The Gerrit database has been decommissioned. Instead of a relational database, Gerrit now stores the needed data directly in the git repositories and creates indices to speed up access, also known has secondary index. These indices are Lucene indices and H2 (ok, this is kind of a small scale relational database).
Git repositories are stored at `/srv/gerrit/git/`
Gerrit uses the LDAP instance shared with Wikimedia Cloud Services and various other things, for authentication. Accounts under ou=people,dc=wikimedia,dc=org and groups under ou=groups,dc=wikimedia,dc=org are exposed to Gerrit. The Gerrit account name is the
cn field in LDAP. In order to log in to Gerrit, a user needs to already have a Wikimedia developer account. See Help:Getting Started for the process of getting a developer account.
To find out what version of Gerrit is running, you can use either of the following two commands:
java -jar /var/lib/gerrit2/review_site/bin/gerrit.war version ssh -p 29418 gerrit.wikimedia.org gerrit version
As of November 2020, Gerrit runs with Java 8.
Since the Gerrit v3.2 upgrade in summer 2020, our Gerrit uses git repos (with indices) instead of a conventional, relational database. They are created/inited automatically during setup.
(We're leaving this section around for a bit, as a missing Database section might otherwise look like an oversight)
- Install OpenJDK 8 and git (
gitpackages on Debian)
- Bazel is required (as of July 2020 at least bazel 3.4.1, can be checked in
Instead of installing Bazel directly, consider installing Bazelisk, which is a Bazel frontend that automatically installs the needed Bazel version for the Gerrit branch you are working on. Bazelisk saves you a lot of trouble when building Gerrit, so if you can, use it.
Update our repository
- Clone gerrit and submodules and add upstream as a remoteOur repository HEAD points to the branch holding the material for the deployment
git clone https://gerrit.wikimedia.org/r/operations/software/gerrit cd gerrit git remote add upstream https://gerrit.googlesource.com/gerrit
- Checkout the
stable-3.2branch (as of November 2020) that tracks the current upstream release:
git checkout stable-3.2 origin/stable-3.2
- Fetch the upstream branch and fast-forward our copy of their branch to the latest tag and push the
stable-3.2directly to Gerrit:
git fetch --tags upstream/stable-3.2 git merge --ff-only v3.2.3 git push --tags origin HEAD:stable-3.2
wmf/stable-3.2and merge the latest tag, push the resulting SINGLE merge commit up for review
git checkout wmf/stable-3.2 git merge v3.2.3
Be sure to not loose I1e63b5bd07d7c351bb51bd6b205d09f730bc8f91 . The change reverts Gerrit's dropping of the jsonevent-layout library which we require in our log4j configuration to format some logs as json. So we either need to keep it in the
WAR file (which is what this commit does), or we need to bring the library into Gerrit's classpath through some other means. See https://phabricator.wikimedia.org/T268020
If this commit is lost at some point and the jsonevent-layout library does not get added through other means, json logging will stop working, and Gerrit logs won't get picked up for Logstash injection.
Next update git submodules. The .gitmodules file comes from upstream and uses relative urls. Since your work copy points to our Gerrit, the submodules would be fetched from our Gerrit. Instead we have to instruct git to rewrite the URLs and use the upstream repositories using the git setting url.<base>.insteadOf = <our url>:
- Update git submodules from the upstream repository: Resolve any conflicts that may arise
git -c url."https://gerrit.googlesource.com".insteadOf="$(dirname $(git config --get remote.origin.url))" submodule update --init
- Push for review. At this point, you will likely be ahead of
wmf/stable-3.2by...quite a bit (hundreds of patches). This is all within a single merge commit though, so Be Bold — push up your changes:
git push origin HEAD:refs/for/wmf/stable-3.2%topic=v3.2.3
Fetch our additional plugins
As our Gerrit instance runs some plugins which are not part of Gerrit upstream set of plugins, we need to fetch them. Some plugins support out-of-tree builds, but the most stable approach is to simply clone them into directories underneath Gerrit's
plugins directory in a checkout of our wmf/stable-3.2 branch. You can use the following short bash script (which assumes you can
ssh to our Gerrit and you have got
jq installed) to clone the needed repositories:
#!/bin/bash set -e set -o pipefail INSTALLED_PLUGINS="$(ssh -p 29418 gerrit.wikimedia.org gerrit plugin ls --format JSON | jq --raw-output 'keys | .')" DEPENDENCIES_FOR_BUILDING="its-base" cd plugins for PLUGIN in $INSTALLED_PLUGINS $DEPENDENCIES_FOR_BUILDING do if [ ! -e "$PLUGIN" ] then echo "Cloning $PLUGIN ..." git clone "https://gerrit.googlesource.com/plugins/$PLUGIN" fi done echo "Success. All needed plugins cloned."
Knowing which branch to choose for which repo is not so straight forward, and hence it's missing from the script. If a plugin (most don't) provide version tags, use them if you're building Gerrit for a specific version. Otherwise, many plugins come with
stable- branches. Use the one for the Gerrit version you're building. If a plugin does not offer any of these, try the
Please go through each of the plugins individually to find the tag/branch that best fits your desired target. There are only 20 or so plugins, so while it's annoying, it won't take ages.
To be tested, checkout tag, fallback to branch, and finally to master:
# Checkout tag or branch or master for PLUGIN in $INSTALLED_PLUGINS; do ( cd $PLUGIN git checkout v3.2.3 || git checkout stable-3.2 || git checkout master ); done; # Show the resolved branch or tag if HEAD is detached for PLUGIN in $INSTALLED_PLUGINS; do ( cd $PLUGIN echo $PLUGIN git branch --points-at=HEAD ) done;
Fix-up of gitiles plugin
gitiles plugin per default fetches fonts directly from Google. Since that's a third party dependency that we do not want, we instead want gitiles to use the fonts that Gerrit itself offers.
To achieve that, make sure your gitiles code includes change I4f4a0b7dd575cbc27641063e05d13b8a43a51d8b. The change did not get much traction upstream, so it probably won't land there. We nonetheless want to include that change.
Fix-up of javamelody plugin
javamelody plugin comes with external dependencies. Gerrit's build system does not automatically pick them up. To allow Gerrit to build the plugin, merge the contents of
plugins/javamelody/external_plugin_deps.bzl into Gerrit's own
Fix-up of zuul plugin
zuul does not support PolyGerrit. Since we want to use the plugin within PolyGerrit, make sure you include the whole stream of commit up to I85549ae4b262c144a10aae812755e965f20637b8 to get a working PolyGerrit. Upstream reviewed a few of these patches. But as the plugin lacks a maintainer, the changes probably won't land soonish there.
- Checkout the
wmf/stable-3.2(as of November 2020)
git checkout -b wmf/stable-3.2 origin/wmf/stable-3.2
Production uses Java 8 as of November 19th 2020 which we will eventually switch to Java 11 ( https://phabricator.wikimedia.org/T268225 ). Meantime, Bazel has to be pointed to your local Java 8 installation:
- Build the
JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64 bazel build release
Note that if your building Gerrit v3.3 (or later) or master from 2020-10-06 (or later) and you're targeting Java 8, you'll also have to add the argument
--java_toolchain=//tools:error_prone_warnings_toolchain (this is untested, but claimed on the gerrit mailing list).
- Build the plugin
for PLUGIN in $(ssh gerrit.wikimedia.org gerrit plugin ls --format JSON | jq --raw-output 'keys | .') ; do bazel build --workspace_status_command="python ./tools/workspace_status_release.py" plugins/$PLUGIN ; done
Current Bazel version is 0.18.1, expected at least 0.19.0
- Bazel updates all the time, update your bazel version from the bazel website (ensure you verify the version signature with the [ https://bazel.build/bazel-release.pub.gpg bazel-release.pub.gpg] key. Or even better: Use Bazelisk, which is a transparent wrapper for Bazel that takes care of preparing the correct version for you.
curl: (35) error:1425F102:SSL routines:ssl_choose_client_version:unsupported protocol
- bazel shells out to curl to download things and, sadly,
repo.eclipse.orgonly supports TLSv1
openssl s_client -connect repo.eclipse.org:443 -tls1. You can modify your openssl settings in
/etc/ssl/openssl.cnf. If your
MinProtocolis set to
TLSv1.2(because you're awesome) — change it to
TLSv1(because not everyone is awesome). Be sure to change it back when you're done.
- Copy the resulting
bazel-bin/plugins/$PLUGIN/$PLUGIN.jarto somewhere safe
- Checkout the
deploy/wmf/stable-Xbranch that aligns with the build branch
- Copy in the
release.waryou saved as
- Copy all the plugin jars over to
./pluginsin the deploy branch
- Commit the changes, upload to Gerrit, etc
./upload_artifacts.py --version=2.15.2 gerrit.war plugins/foo.jar ...for the core application and all updated plugins (cf: Archiva, specifically setting up your
- Note: Alternatively, you can upload them by using the web UI, but that gets repetitive over a bunch of plugins so I wrote the tool above
- SSH to the deployment master
- Navigate to
- Fetch & checkout the appropriate
- Deploy to gerrit2001 to ensure that there are no errors with git-fat et al
scap deploy -l gerrit2001.wikimedia.org 'Gerrit to [version] on gerrit2001'
- Deploy to gerrit1001
scap deploy -l gerrit1001.wikimedia.org 'Gerrit to [version] on gerrit1001'
- If you're only deploying plugins, you're done, otherwise SSH to the Gerrit master and issue
sudo service gerrit restart
Upgrading the database
Since our Gerrit v3.2 upgrade in summer 2020, our Gerrit no longer uses a relational database. So this section is obsolete.
If you need to restart Gerrit (e.g. because it is OOMing), run
sudo systemctl restart gerrit. This will take a few seconds before it comes back.
Example migration ticket (cobalt -> gerrit1001): https://phabricator.wikimedia.org/T222391
Topic branch from gerrit1001 migration: https://gerrit.wikimedia.org/r/q/topic:%22gerrit1001%22+(status:open%20OR%20status:merged)
Follow these steps to migrate from one server to another:
Make sure you run rsync with --delete
- Rsync /srv/gerrit/git/ , /srv/gerrit/plugins and /var/lib/gerrit2/review_site/ from <old_host> to <new_host>
rsync --archive --verbose --delete /srv/gerrit/git/ rsync://<new_host>.wikimedia.org/gerrit-data/git/
rsync --archive --verbose --delete /srv/gerrit/plugins/ rsync://<new_host>.wikimedia.org/gerrit-data/plugins/
rsync --archive --verbose --delete /var/lib/gerrit2/review_site/ rsync://<new_host>.wikimedia.org/gerrit-var-lib/
(Note: We are using rsync protocol directly and 'gerrit-data' and 'gerrit-var-'lib' are the names of rsync modules, not file system pathes. They are defined in "class profile::gerrit::migration".)
- Stop gerrit && disable puppet on <new_host>
- Create something similar to https://gerrit.wikimedia.org/r/#/c/operations/puppet/+/535966/
- Stop puppet on <old_host> + <replica>
- Create something similar to https://gerrit.wikimedia.org/r/#/c/operations/puppet/+/541110/
- Create something similar to https://gerrit.wikimedia.org/r/#/c/operations/dns/+/541111/
- Stop gerrit on <old_host>
- Repeat the rsync commands above.
- Rename /var/lib/gerrit2/review_site/data/javamelody/r_<old_host> to /var/lib/gerrit2/review_site/data/javamelody/r_<new_host> on <new_host>.
- Run puppet on <new_host> + <old_host>
- Start gerrit on <new_host>
- Hack DNS authdns-update to clone from gerrit-replica temporarily, deploy DNS change
- Manually copy apache2 site config for gerrit.wm.org with scp from <old_host> to <new_host>, restart apache
- Manually run command from list_mediawiki_extensions cron to create /var/www/mediawiki-extensions.txt
- Run the online reindexer
- Decom <old_host> (create a ticket like https://phabricator.wikimedia.org/T236187)
Creating new repositories
Inspecting an account settings
Since Gerrit 2.15, accounts are stored in
All-Users.git. One first need to find the account reference, that can be done by checking which references a user can read on All-Users.git:
$ ssh -p 29418 gerrit.wikimedia.org gerrit ls-user-refs --project All-Users --user 'firstname.lastname@example.org' refs/meta/config refs/users/34/1234 refs/users/self $
Note: for accounts having extended permissions on
All-Users.git, that will show all references which is not useful.
Then on the server side (or remotely if you have privileges), you can list the configuration files and dump their content:
$ cd /srv/gerrit/git/All-Users.git $ git ls-tree refs/users/34/1234 100644 blob xxx account.config 100644 blob yyy authorized_keys 100644 blob zzz preferences.confg 100644 blob ddd watch.config $ git show refs/users/34/1234:authorized_keys ssh-rsa AAAAxyz... RSA-1024
All-Users database can be browsed locally via git. The easiest way to find a user given the
All-Users git repo is to git-grep for the username or email in the
$ mkdir All-Users && cd All-Users && git init $ git pull https://gerrit.wikimedia.org/r/All-Users refs/meta/external-ids $ git grep johndoe
Become an Administrator
Being an administrator grants all global capabilities as described at Gerrit Access Control - global capabilities.
If right is given as a one off, one would most probably want to be removed from the group once the rights are no more required.
Disabling / Blocking an account
This action is limited to Gerrit administrators.
If an account needs to be disabled for some reason, there's two steps to complete:
- remove the ssh keys
- set the account to inactive
To set an account inactive, use this command:
$ ssh gerrit.wikimedia.org -p 29418 gerrit set-account --inactive <Username here>
To enable the user again:
$ ssh gerrit.wikimedia.org -p 29418 gerrit set-account --active <Username or user id here>
If you get an error that the user can't be found, try using the user id instead (can be obtained by grepping the all-users database).
And flush the accounts cache on the replica:
$ ssh gerrit-replica.wikimedia.org -p 29418 gerrit flush-caches --cache accounts
Flush all sessions
Do not flush all sessions when banning a single user. As of May 2019 setting a user to inactive should invalidate their session automagically
web_sessions caches makes everyone re-login (aka, the sledgehammer). It should not be necessary in most circumstances; however, the command is still in this documentation in case it is needed in an unforeseen situation:
$ ssh -p 29418 gerrit.wikimedia.org gerrit flush-caches --cache web_sessions
gerrit1001.wikimedia.org there is
/root/unfirewall.sh, which will shut off access to Gerrit HTTP(S) and SSH.
Opsen will find them fairly self-explanatory.
Gerrit queue tasks, given you have the appropriate permission you can run either of:
$ ssh -p 29418 gerrit.wikimedia.org ps -w $ ssh -p 29418 gerrit.wikimedia.org gerrit show-queue -w
Tasks can be stuck which starve Gerrit processing. For example people would no more be able to fetch. In such a case, granted you are in the Administrators group you can kill a task by id:
$ ssh -p 29418 gerrit.wikimedia.org kill <SOMEID>
Forcing Replication re-runs
When forcing a replication run through gerrit's replication plugin, stay clear of the
--all switch, as it breaks renamed projects on github.
For example, both gerrit and github have a
mediawiki repository. But github's
mediawiki repository is actually
mediawiki/core in gerrit. As gerrit also has a
mediawiki repository, forcing replication on all projects would push gerrit's
mediawiki repository onto github's
mediawiki repository. Thereby, github's
mediawiki repository falls over, and for examples the release tags from github's
mediawiki are gone (cf. task T100409).
This currently (2015-05-28) affects us for at least for the following repos:
|Gerrit's name||Overloaded name on GitHub|
If you by accident forced replication with
--all, force replication of the effective gerrit repos to make up for it (i.e.:
As of July 2018 replication to github requires a repository to be manually created on github using the naming scheme gerrit expects, i.e.
/ replaced with
Github owners will be able to create these repositories.
Once a repository is created, replication to that repo can be forced using the gerrit replication ssh command.
$ ssh -p 29418 gerrit.wikimedia.org replication start operations/debs/trafficserver --wait
mediawiki-replication must be allowed to read
refs/heads/* for replication to GitHub to work. This is because it is currently set as the
etc inside the Gerrit repository home.
replication_log should be checked in addition to the
gerrit.log for mention of anything that could be wrong with replication.
Any changes to
replication.config should be followed with a restart of the gerrit service to ensure that those changes are active. There is a bug with the replication plugin where it will reload the
replication.config (and acknowledge that the configuration has been reloaded in the logs), but actually operate with a broken configuration in an unknown state until a restart.
ORES mirroring setup is dangerous and unusual, but should, nevertheless, be documented.
The canonical repository for ORES lives on github. This is repository is observed by diffusion. This can done in the
Manage Repository section of diffusion code browser. From there, phabricator "Mirrors" that repository (also available in diffusion management settings) to gerrit.
This setup is discouraged.
How to setup Gerrit in a Cloud VPS project
JavaMelody monitors the state of the Gerrit JVM. They are collected by Prometheus from https://gerrit.wikimedia.org/r/monitoring?prometheus
- JavaMelody in Gerrit (only accesible to logged-in Gerrit Administrators/Gerrit Managers)
- Grafana "Gerrit" folder"
- Memory Usage
- GC Timing
- Grafana GC Timing
- Garbage collection metrics. Times in the 100s of milliseconds, rather than in the 10s of milliseconds can be indicative of a problem (running low on memory)
- Active Threads
On top of the JavaMelody data, Gerrit has internal metrics.
Which obviously requires authentication. That complements
We use the metrics-reporter-prometheus plugin which exposes collected by Prometheus from https://gerrit.wikimedia.org/r/plugins/metrics-reporter-prometheus/metrics . Those Gerrit metrics can also be seen on the JavaMelody MBeans page under the
Logs are available on the gerrit servers at:
/var/log/gerrit/. There are a number of logfiles:
gerrit.log: This is the main log file and will show stacktraces and errors
gerrit.logbug not really human readable. For sending structured logs to logstash.
sshd_log: Log of sshd events
gc_log: Logs for
git gcnot the JVM garbage collection (those logs are available in
plugin_log: Info about plugins being loaded and reloaded, this information is also in
Gerrit sits behind apache. Apache access and error logs are both in
Gerrit's logs are sent to logstash using log4j. You can find its logs by searching with
A thread dump is often useful in troubleshooting. To capture a thread dump use
jstack. This code should be safe to run at any time, and is run frequently while Gerrit is running:
sudo -u gerrit2 jstack -l $(pgrep java) > "/srv/gerrit/jstack-$(date +%Y-%m-%d-%H%M%S).dump"
It's often useful to upload the resulting file to https://fastthread.io/ to detect problems.
This command isn't run very often, unsure how safe it is to run; kept here for folks who are familiar with jstat
Display a summary of garbage collection statistics every 1000 ms:
sudo -u gerrit2 /usr/lib/jvm/java-8-openjdk-amd64/bin/jstat -gcutil "$(pgrep -u gerrit2 java)" 1000
Java heap usage
Requires openjdk-X-dbg for the debugging symbols
sudo /usr/lib/jvm/java-8-openjdk-amd64/bin/jmap -heap "$( pgrep -u gerrit2 java)"
Troubleshooting / upgrade FAQ
Frequently asked questions regarding issues since the recent Gerrit version upgrade to 3.2.
Plugin install error: TypeError: self.onAction is not a function
If you see this error please hard refresh your browser cache.
For some the Ctrl + F5 or Stift + Ctrl + F5 (or whatever combination your browser wants) is not sufficient.
If you still run into the issue after pressing your browsers F5 combination, please try clearing your caches for good.
For example on Firefox follow steps 1-6 from
If you use a different browser, it should allow you to clear cached web content somewhere in the setting too. Please find that in your browser's help pages and follow the instructions.
Can't upload any patches with git review
If you use git-review to submit patches to gerrit, make sure you have 1.27 or newer (not 1.26). git-review 1.26 does not work with the new gerrit version.