Gerrit on Kubernetes

Gerrit is a web-based code review tool, which acts as a Git server. This helm chart provides a Gerrit setup that can be deployed on Kubernetes. In addition, the chart provides a CronJob to perform Git garbage collection.

Prerequisites

• Helm (>= version 3.0)

  (Check out this guide how to install and use helm.)

• Access to a provisioner for persistent volumes with Read Write Many (RWM)- capability.

  A list of applicaple volume types can be found here. This project was developed using the NFS-server-provisioner helm chart, a NFS-provisioner deployed in the Kubernetes cluster itself. Refer to this guide of how to deploy it in context of this project.

• A domain name that is configured to point to the IP address of the node running the Ingress controller on the kubernetes cluster (as described here).

• (Optional: Required, if SSL is configured) A Java keystore to be used by Gerrit.

Installing the Chart

To install the chart with the release name gerrit, execute:

cd $(git rev-parse --show-toplevel)/helm-charts
helm install \
  gerrit \  # release name
  ./gerrit \  # path to chart
  -f <path-to-custom-values>.yaml

The command deploys the Gerrit instance on the current Kubernetes cluster. The configuration section lists the parameters that can be configured during installation.

Configuration

The following sections list the configurable values in values.yaml. To configure a Gerrit setup, make a copy of the values.yaml-file and change the parameters as needed. The configuration can be applied by installing the chart as described above.

In addition, single options can be set without creating a custom values.yaml:

cd $(git rev-parse --show-toplevel)/helm-charts
helm install \
  gerrit \  # release name
  ./gerrit \  # path to chart
  --set=gitRepositoryStorage.size=100Gi

Container images

Storage classes

For information of how a StorageClass is configured in Kubernetes, read the official Documentation.

Network policies

The NetworkPolicies provided here are quite strict and do not account for all possible scenarios. Thus, custom NetworkPolicies have to be added, e.g. for allowing Gerrit to replicate to a Gerrit replica. By default, the egress traffic of the gerrit pod is blocked, except for connections to the DNS-server. Thus, replication which requires Gerrit to perform git pushes to the replica will not work. The chart provides the possibility to define custom rules for egress- traffic of the gerrit pod under gerrit.networkPolicy.egress. Depending on the scenario, there are different ways to allow the required connections. The easiest way is to allow all egress-traffic for the gerrit pods:

gerrit:
  networkPolicy:
    egress:
    - {}

If the remote that is replicated to is running in a pod on the same cluster and the service-DNS is used as the remote's URL (e.g. http://gerrit-replica-git-backend-service:80/git/${name}.git), a podSelector (and namespaceSelector, if the pod is running in a different namespace) can be used to whitelist the traffic:

gerrit:
  networkPolicy:
    egress:
    - to:
      - podSelector:
          matchLabels:
            app: git-backend

If the remote is outside the cluster, the IP of the remote or its load balancer can also be whitelisted, e.g.:

gerrit:
  networkPolicy:
    egress:
    - to:
      - ipBlock:
          cidr: xxx.xxx.0.0/16

The same principle also applies to other use cases, e.g. connecting to a database. For more information about the NetworkPolicy resource refer to the Kubernetes documentation.

Storage for Git repositories

If the git repositories should be persisted even if the chart is deleted and in a way that the volume containing them can be mounted by the reinstalled chart, the PVC claiming the volume has to be created independently of the chart. To use the external PVC, set gitRepositoryStorage.externalPVC.enabled to true and give the name of the PVC under gitRepositoryStorage.externalPVC.name.

CA certificate

Some application may require TLS verification. If the default CA built into the containers is not enough a custom CA certificate can be given to the deployment. Note, that Gerrit will require its CA in a JKS keytore, which is described below.

Ingress

Git garbage collection

Gerrit

Gerrit config files

The gerrit chart provides a ConfigMap containing the configuration files used by Gerrit, e.g. gerrit.config and a Secret containing sensitive configuration like the secure.config to configure the Gerrit installation in the Gerrit component. The content of the config files can be set in the values.yaml under the keys gerrit.etc.config and gerrit.etc.secret respectively. The key has to be the filename (eg. gerrit.config) and the file's contents the value. This way an arbitrary number of configuration files can be loaded into the $GERRIT_SITE/etc-directory, e.g. for plugins. All configuration options for Gerrit are described in detail in the official documentation of Gerrit. Some options however have to be set in a specified way for Gerrit to work as intended with the chart:

• gerrit.basePath

  Path to the directory containing the repositories. The chart mounts this directory from a persistent volume to /var/gerrit/git in the container. For Gerrit to find the correct directory, this has to be set to git.

• gerrit.serverId

  In Gerrit-version higher than 2.14 Gerrit needs a server ID, which is used by NoteDB. Gerrit would usually generate a random ID on startup, but since the gerrit.config file is read only, when mounted as a ConfigMap this fails. Thus the server ID has to be set manually!

• gerrit.canonicalWebUrl

  The canonical web URL has to be set to the Ingress host.

• index.onlineUpgrade

  Online reindexing is currently NOT supported. An offline reindexing will be enforced upon Gerrit updates. Online reindexing might under some circum- stances interfere with the Gerrit pod startup procedure and thus has to be deactivated.

• httpd.listenURL

  This has to be set to proxy-http://*:8080/ or proxy-https://*:8080, depending of TLS is enabled in the Ingress or not, otherwise the Jetty servlet will run into an endless redirect loop.

• httpd.gracefulStopTimeout / sshd.gracefulStopTimeout

  To enable graceful shutdown of the embedded jetty server and SSHD, a timeout has to be set with this option. This will be the maximum time, Gerrit will wait for HTTP requests to finish before shutdown.

• container.user

  The technical user in the Gerrit container is called gerrit. Thus, this value is required to be gerrit.

• container.javaHome

  This has to be set to /usr/lib/jvm/java-11-openjdk-amd64, since this is the path of the Java installation in the container.

• container.javaOptions

  The maximum heap size has to be set. And its value has to be lower than the memory resource limit set for the container (e.g. -Xmx4g). In your calculation, allow memory for other components running in the container.

To enable liveness- and readiness probes, the healthcheck plugin will be installed by default. Note, that by configuring to use a packaged or downloaded version of the healthcheck plugin, the configured version will take precedence over the default version. The plugin is by default configured to disable the querychanges and auth healthchecks, since these would not work on a new and empty Gerrit server. The default configuration can be overwritten by adding the healthcheck.config file as a key-value pair to gerrit.etc.config as for every other configuration.

SSH keys should be configured via the helm-chart using the gerrit.etc.secret map. Gerrit will create its own keys, if none are present in the site, but if multiple Gerrit pods are running, each Gerrit instance would have its own keys. Users accessing Gerrit via a load balancer would get issues due to changing host keys.

Installing Gerrit plugins

There are several different ways to install plugins for Gerrit:

• RECOMMENDED: Package the plugins to install into the WAR-file containing Gerrit. This method provides the most stable way to install plugins, but requires to use a custom built gerrit-war file and container images, if plugins are required that are not part of the official release.war-file.

• Download and cache plugins. The chart supports downloading the plugin files and to cache them in a separate volume, that is shared between Gerrit-pods. SHA1- sums are used to validate plugin-files and versions.

• Download plugins, but do not cache them. This should only be used during development to save resources (the shared volume). Each pod will download the plugin-files on its own. Pods will fail to start up, if the download-URL is not valid anymore at some point in time.

Upgrading the Chart

To upgrade an existing installation of the gerrit chart, e.g. to install a newer chart version or to use an updated custom values.yaml-file, execute the following command:

cd $(git rev-parse --show-toplevel)/helm-charts
helm upgrade \
  <release-name> \
  ./gerrit \ # path to chart
  -f <path-to-custom-values>.yaml

Uninstalling the Chart

To delete the chart from the cluster, use:

helm delete <release-name>