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Gerrit Operator

Development

Development processes are documented here.

Prerequisites

Deploying Gerrit using the operator requires some additional prerequisites to be fulfilled:

Shared Storage (ReadWriteMany)

Gerrit instances share the repositories and other data using shared volumes. Thus, a StorageClass and a suitable provisioner have to be available in the cluster. An example for such a provisioner would be the NFS-subdir-external-provisioner.

Ingress provider

The Gerrit Operator will also set up network routing rules and an ingress point for the Gerrit instances it manages. The network routing rules ensure that requests will be routed to the intended GerritCluster component, e.g. in case a primary Gerrit and a Gerrit Replica exist in the cluster, git fetch/clone requests will be sent to the Gerrit Replica and all other requests to the primary Gerrit.

You may specify the ingress provider by setting the INGRESS environment variable in the operator Deployment manifest. That is, the choice of an ingress provider is an operator-level setting. However, you may specify some ingress configuration options (host, tls, etc) at the GerritCluster level, via GerritClusterIngressConfig.

The Gerrit Operator currently supports the following Ingress providers:

  • NONE

    The operator will install no Ingress components. Services will still be available. No prerequisites are required for this case.

    If spec.ingress.enabled is set to true in GerritCluster, the operator will still configure network related options like http.listenUrl in Gerrit based on the other options in spec.ingress.

  • INGRESS

    The operator will install an Ingress. Currently only the Nginx-Ingress-Controller is supported, which will have to be installed in the cluster and has to be configured to allow snippet configurations. An example of a working deployment can be found here.

    SSH support is not fully managed by the operator, since it has to be enabled and configured in the nginx ingress controller itself.

  • ISTIO

    The operator supports the use of Istio as a service mesh. An example on how to set up Istio can be found here.

  • AMBASSADOR

    The operator also supports Ambassador for setting up ingress to the Gerrits deployed by the operator. If you use Ambassador's "Edge Stack" or "Emissary Ingress" to provide ingress to your k8s services, you should set INGRESS=AMBASSADOR. Currently, SSH is not directly supported when using INGRESS=AMBASSADOR.

Deploy

You will need to have admin privileges for your k8s cluster in order to be able to deploy the following resources.

You may choose to deploy the operator resources using helm, or directly via kubectl apply.

Using helm charts

Make sure you have helm installed in your environment.

There are two relevant helm charts.

gerrit-operator-crds

This chart installs the CRDs (k8s API extensions) to your k8s cluster. No chart values need to be modified. The build initiated by the mvn install command from the Publish section includes a step that updates the CRDs in this helm chart to reflect any changes made to them in the operator source code. The CRDs installed are: GerritCluster, Gerrit, GitGarbageCollection, Receiver.

You do not need to manually helm install this chart; this chart is installed as a dependency of the second gerrit-operator helm chart as described in the next subheading.

gerrit-operator

This chart installs the gerrit-operator-crds chart as a dependency, and the following k8s resources:

  • Deployment
  • ServiceAccount
  • ClusterRole
  • ClusterRoleBinding

The operator itself creates a Service resource and a ValidationWebhookConfigurations resource behind the scenes.

You will need to modify the values in helm-charts/gerrit-operator/values.yaml to point the chart to the registry/org that is hosting the Docker container image for the operator (from the Publish step earlier). Now,

run:

# Create a namespace for the gerrit-operator
kubectl create ns gerrit-operator

# Build the gerrit-operator-crds chart and store it in the charts/ subdirectory
helm dependency build helm-charts/gerrit-operator/

# Install the gerrit-operator-crds chart and the gerrit-operator chart
helm -n gerrit-operator install gerrit-operator helm-charts/gerrit-operator/

The chart itself, and all the bundled namespaced resources, are installed in the gerrit-operator namespace, as per the -n option in the helm command.

Without the helm charts

First all CustomResourceDefinitions have to be deployed:

kubectl apply -f operator/target/classes/META-INF/fabric8/*-v1.yml

Note that these do not include the -v1beta1.yaml files, as those are for old Kubernetes versions.

The operator requires a Java Keystore with a keypair inside to allow TLS verification for Kubernetes Admission Webhooks. To create a keystore and encode it with base64, run:

keytool \
  -genkeypair \
  -alias operator \
  -keystore keystore \
  -keyalg RSA \
  -keysize 2048 \
  -validity 3650
cat keystore | base64 -b 0

Add the result to the Secret in k8s/operator.yaml (see comments in the file) and also add the base64-encoded password for the keystore to the secret.

Then the operator and associated RBAC rules can be deployed:

kubectl apply -f operator/k8s/rbac.yaml
kubectl apply -f operator/k8s/operator.yaml

k8s/operator.yaml contains a basic deployment of the operator. Resources, docker image name etc. might have to be adapted. For example, the ingress provider has to be configured by setting the INGRESS environment variable in operator/k8s/operator.yaml to either NONE, INGRESS, ISTIO, or AMBASSADOR.

Updating

The Gerrit Operator helm chart can be updated by running:

# Rebuild the gerrit-operator-crds chart and store it in the charts/ subdirectory
helm dependency build helm-charts/gerrit-operator/

# Install the gerrit-operator-crds chart and the gerrit-operator chart
helm -n gerrit-operator upgrade gerrit-operator helm-charts/gerrit-operator/

The Gerrit Operator will automatically reconcile all CustomResources in the cluster on startup.

The GerritOperator will always only support two versions of the CRDs. The newer version will always be the one that will be stored in ETCD. Conversion will happen automatically during the update. Note, that this means that updates over multiple versions will not work, but updates that include CRD version updates have to be done in sequence.

CustomResources

The operator manages several CustomResources that are described in more detail below.

The API reference for all CustomResources can be found here.

GerritCluster

The GerritCluster CustomResource installs one or multiple Gerrit instances. The operator takes over managing the state of all Gerrit instances within the cluster and ensures that the state stays in sync. To this end it manages additional resources that are shared between Gerrit instances or are required to synchronize the state between Gerrit instances. These additional resources include:

  • storage
  • network / service mesh

Installing Gerrit with the GerritCluster resource is highly recommended over using the Gerrit CustomResource directly, even if only a single deployment is installed, since this reduces the requirements that have to be managed manually. The same holds true for the Receiver CustomResource, which without a Gerrit instance using the same site provides little value.

For now, only a single Gerrit CustomResource using each mode can be deployed in a GerritCluster, e.g. one primary Gerrit and one Gerrit Replica. The reason for that is, that there is currently no sharding implemented and thus multiple deployments don't bring any more value than just scaling the existing deployment. Instead of a primary Gerrit also a Receiver can be installed.

Gerrit

The Gerrit CustomResource deploys a Gerrit, which can run in multiple modes.

The Gerrit-CustomResource is mainly meant to be used by the GerritCluster-reconciler to install Gerrit-instances managed by a GerritCluster. Gerrit-CustomResources can however also be applied separately. Note, that the Gerrit operator will then not create any storage resources or setup any network resources in addition to the service.

GitGarbageCollection

The GitGarbageCollection-CustomResource is used by the operator to set up CronJobs that regularly run Git garbage collection on the git repositories that are served by a GerritCluster.

A GitGarbageCollection can either handle all repositories, if no specific repository is configured or a selected set of repositories. Multiple GitGarbageCollections can exist as part of the same GerritCluster, but no two GitGarbageCollections can work on the same project. This is prevented in three ways:

  • ValidationWebhooks will prohibit the creation of a second GitGarbageCollection that does not specify projects, i.e. that would work on all projects.
  • Projects for which a GitGarbageCollections that specifically selects it exists will be excluded from the GitGarbageCollection that works on all projects, if it exists.
  • ValidationWebhooks will prohibit the creation of a GitGarbageCollection that specifies a project that was already specified by another GitGarbageCollection.

Receiver

NOTE: A Receiver should never be installed for a GerritCluster that is already managing a primary Gerrit to avoid conflicts when writing into repositories.

The Receiver-CustomResource installs a Deployment running Apache with a git-http- backend that is meant to receive pushes performed by Gerrit's replication plugin. It can only be installed into a GerritCluster that does not include a primary Gerrit, but only Gerrit Replicas.

The Receiver-CustomResource is mainly meant to be used by the GerritCluster-reconciler to install a Receiver-instance managed by a GerritCluster. Receiver-CustomResources can however also be applied separately. Note, that the Gerrit operator will then not create any storage resources or setup any network resources in addition to the service.

GerritNetwork

The GerritNetwork CustomResource deploys network components depending on the configured ingress provider to enable ingress traffic to GerritCluster components.

The GerritNetwork CustomResource is not meant to be installed manually, but will be created by the Gerrit Operator based on the GerritCluster CustomResource.

IncomingReplicationTask

A regularly running task to fetch repositories from a different git server that is not necessarily a Gerrit to the local Gerrit. This job can also be used to fetch a subset of refs into an existing repository in Gerrit, e.g. branches from a forked repository could be fetched into a ref namespace of the fork residing in Gerrit.

Only fetching via HTTP(S) is supported at the moment. SSH can't be used for fetches.

Configuration of Gerrit

The operator takes care of all configuration in Gerrit that depends on the infrastructure, i.e. Kubernetes and the GerritCluster. This avoids duplicated configuration and misconfiguration.

This means that some options in the gerrit.config are not allowed to be changed. If these values are set and are not matching the expected value, a ValidationWebhook will reject the resource creation/update. Thus, it is best to not set these values at all. To see which values the operator assigned check the ConfigMap created by the operator for the respective Gerrit.

These options are:

  • cache.directory

    This should stay in the volume mounted to contain the Gerrit site and will thus be set to cache.

  • 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 = -Djavax.net.ssl.trustStore

    The keystore will be mounted to /var/gerrit/etc/keystore.

  • container.replica

    This has to be set in the Gerrit-CustomResource under spec.isReplica.

  • container.user

    The technical user in the Gerrit container is called gerrit.

  • gerrit.basePath

    The git repositories are mounted to /var/gerrit/git in the container.

  • gerrit.canonicalWebUrl

    The canonical web URL has to be set to the hostname used by the Ingress/Istio.

  • 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.

  • sshd.advertisedAddress

    This is only enforced, if Istio is enabled. It can be configured otherwise.

  • sshd.listenAddress

    Since the container port for SSH is fixed, this will be set automatically. If no SSH port is configured in the service, the SSHD is disabled.

Feature toggles

This section is dedicated to explain what are the feature toggles and how to set each one of them.

Cluster Mode

The introduction of this enumeration allows the provision of Gerrit in different modes.

It is defined by an environment variable called CLUSTER_MODE, that can have the values of:

  • HIGH_AVAILABILITY
  • MULTISITE

By default, the mode is set to HIGH_AVAILABILITY.

In case of provision Gerrit in MULTISITE mode, only ISTIO will be supported as ingress provider.

It can be configured either by:

With helm charts

The environment variable CLUSTER_MODE is set by the helm chart property cluster.mode.

Without helm charts

The environment variable CLUSTER_MODE is set in the Operator K8s Deployment Resource.

Minikube

This chapter gives a short walkthrough in installing the Gerrit operator and a minimal GerritCluster in minikube. It is meant as an entrypoint for new users and developers to get familiar with deploying the setup.

Prerequisites

The following tools are required for following the guide:

During this guide a lot of components/pods will be started in Minikube. Consider increasing the number of CPUs and RAM that Minikube is allowed to use. This can either be done by configuring the limits in Docker or by using the --cpus=10 and --memory=32000 options.

The guide was tested with 10 CPUs and 32G RAM, but should also work with less resources. With the full setup running without load, 14G RAM and 0.5 CPUs are being used, but during startup of Gerrit more resources are required.

Starting Minikube

First start minikube:

minikube start

Build images

It is highly recommended to build the images manually to ensure that it is compatible with the example resources at the checked out commit:

eval $(minikube docker-env)
./build --tag latest
pushd operator
mvn clean install -Drevision=latest
docker image tag gerrit-operator:latest k8sgerrit/gerrit-operator:latest
popd

Gerrit Operator

Then we can install the Gerrit Operator. This setup will use all the default values, i.e. no ingress provider support will be installed and it will use the latest version.

kubectl create ns gerrit-operator

helm dependency build --verify helm-charts/gerrit-operator
helm upgrade \
  --install gerrit-operator \
  helm-charts/gerrit-operator \
  -n gerrit-operator \
  --set=image.imagePullPolicy=IfNotPresent

NFS

For a GerritCluster a volume with ReadWriteMany capabilities is required. Thus, a NFS provisioner has to be deployed:

kubectl create ns nfs
helm repo add nfs-ganesha-server-and-external-provisioner \
  https://kubernetes-sigs.github.io/nfs-ganesha-server-and-external-provisioner/
helm upgrade \
  --install nfs \
  nfs-ganesha-server-and-external-provisioner/nfs-server-provisioner \
  -n nfs

Primary Gerrit

The Gerrit Operator will not manage secrets itself, since secret data would be exposed in the custom resources. Thus, Secrets have to be applied manually and referenced by name in the GerritCluster CustomResource. To create a Secret containing SSH keys for Gerrit, run:

kubectl create ns gerrit
kubectl apply -f Documentation/examples/gerrit.secret.yaml

Then a simple GerritCluster can be installed:

kubectl apply -f Documentation/examples/1-gerritcluster.yaml

This will install a single primary Gerrit instance without any networking, i.e. it can only be accessed via port-forwarding.

Adding a Gerrit Replica

Next, a Gerrit Replica can be added to the GerritCluster. It will access the repositories from the same filesystem as the primary Gerrit:

diff Documentation/examples/1-gerritcluster.yaml Documentation/examples/2-gerritcluster-with-replica.yaml
kubectl apply -f Documentation/examples/2-gerritcluster-with-replica.yaml

Istio

The Gerrit Operator can also manage network routing configuration in the GerritCluster. To do that we need to install one of the supported Ingress providers like Istio.

To install Istio with default configuration download istioctl:

export ISTIO_VERSION=1.20.3 && curl -L https://istio.io/downloadIstio | sh -
export PATH=$PWD/istio-$ISTIO_VERSION/bin:$PATH

Then install istio:

istioctl install -f istio/gerrit.profile.yaml

Enabling istio sidecar injection in the Gerrit namespace is required to add Gerrit pods to the service mesh:

kubectl label namespace gerrit istio-injection=enabled

To make use of Istio, the operator has to be configured to support Istio as an Ingress provider:

helm upgrade \
  --install gerrit-operator \
  helm-charts/gerrit-operator \
  -n gerrit-operator \
  --set=ingress.type=ISTIO

Next, the Ingress can be enabled in the GerritCluster:

diff Documentation/examples/2-gerritcluster-with-replica.yaml Documentation/examples/3-gerritcluster-istio.yaml
kubectl apply -f Documentation/examples/3-gerritcluster-istio.yaml

To access Gerrit, a tunnel has to be established to the Istio Ingressgateway service and the host. This should be done in a separate shell session.

minikube tunnel

The connection data can be retrieved like this:

export INGRESS_HOST=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
export INGRESS_PORT=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="http2")].port}')
export GATEWAY_URL=$INGRESS_HOST:$INGRESS_PORT
echo $GATEWAY_URL

Add the following line to /etc/hosts (This assumes that $GATEWAY_URL is 127.0.0.1):

127.0.0.1 gerrit.minikube

Gerrit can now be accessed using http://gerrit.minikube. Note, that since a primary and a Gerrit Replica exist in the GerritCluster, the Gerrit Operator will automatically configure Istio to route fetch and clone requests to the Gerrit Replica.

High Availability

As a next step Gerrit can be scaled to provide better availability. This is straightforward for the Gerrit Replica, since it just requires to increase the number of replicas in the Statefulset of Gerrit primaries in the GerritCluster spec:

diff Documentation/examples/3-gerritcluster-istio.yaml  Documentation/examples/4-gerritcluster-ha-replica.yaml
kubectl apply -f Documentation/examples/4-gerritcluster-ha-replica.yaml

For the primary Gerrit, the Gerrit Operator will automatically install and configure the high-availability plugin, if the Primary Gerrit is scaled to 2 or more pod replicas. However, there are some prerequisites.

First, a database to be used for the global refdb is required. In this example, zookeeper will be used:

kubectl create ns zookeeper
kubectl label namespace zookeeper istio-injection=enabled
helm upgrade --install zookeeper oci://registry-1.docker.io/bitnamicharts/zookeeper -n zookeeper

Now, the GerritCluster can be configured to use the Global RefDB

diff Documentation/examples/4-gerritcluster-ha-replica.yaml Documentation/examples/5-gerritcluster-refdb.yaml
kubectl apply -f Documentation/examples/5-gerritcluster-refdb.yaml

This will configure Gerrit to install the global-refdb lib module and the plugin with the configured implementation, in this example Zookeeper. The Gerrit Operator will also set some basic authentication to enable the connection to the database.

For Gerrit to be able to discover its peers, it has to have permissions to get the Gerrit pods deployed in its own namespace from the Kubernetes API server. For that purpose, a ServiceAccount with the corresponding role needs to be created:

kubectl apply -f Documentation/examples/gerrit.rbac.yaml

Now, the primary Gerrit can be scaled up. The ServiceAccount also has to be referenced:

diff Documentation/examples/5-gerritcluster-refdb.yaml Documentation/examples/6-gerritcluster-ha-primary.yaml
kubectl apply -f Documentation/examples/6-gerritcluster-ha-primary.yaml

Now, two primary Gerrit pods are available in the cluster.