Using the GitLab Shell chart

The gitlab-shell sub-chart provides an SSH server configured for Git SSH access to GitLab.

Requirements

This chart depends on access to the Workhorse services, either as part of the complete GitLab chart or provided as an external service reachable from the Kubernetes cluster this chart is deployed onto.

Design Choices

In order to easily support SSH replicas, and avoid using shared storage for the SSH authorized keys, we are using the SSH AuthorizedKeysCommand to authenticate against the GitLab authorized keys endpoint. As a result, we don’t persist or update the AuthorizedKeys file within these pods.

Configuration

The gitlab-shell chart is configured in two parts: external services, and chart settings. The port exposed through Ingress is configured with global.shell.port, and defaults to 22. The Service’s external port is also controlled by global.shell.port.

Installation command line options

Parameter Default Description
annotations   Pod annotations
podLabels   Supplemental Pod labels. Will not be used for selectors.
common.labels   Supplemental labels that are applied to all objects created by this chart.
config.clientAliveInterval 0 Interval between keepalive pings on otherwise idle connections; the default value of 0 disables this ping
config.loginGraceTime 120 Specifies amount of time that the server will disconnect after if the user has not successfully logged in
config.maxStartups.full 100 SSHd refuse probability will increase linearly and all unauthenticated connection attempts would be refused when unauthenticated connections number will reach specified number
config.maxStartups.rate 30 SSHd will refuse connections with specified probability when there would be too many unauthenticated connections (optional)
config.maxStartups.start 10 SSHd will refuse connection attempts with some probability if there are currently more than the specified number of unauthenticated connections (optional)
deployment.livenessProbe.initialDelaySeconds 10 Delay before liveness probe is initiated
deployment.livenessProbe.periodSeconds 10 How often to perform the liveness probe
deployment.livenessProbe.timeoutSeconds 3 When the liveness probe times out
deployment.livenessProbe.successThreshold 1 Minimum consecutive successes for the liveness probe to be considered successful after having failed
deployment.livenessProbe.failureThreshold 3 Minimum consecutive failures for the liveness probe to be considered failed after having succeeded
deployment.readinessProbe.initialDelaySeconds 10 Delay before readiness probe is initiated
deployment.readinessProbe.periodSeconds 5 How often to perform the readiness probe
deployment.readinessProbe.timeoutSeconds 3 When the readiness probe times out
deployment.readinessProbe.successThreshold 1 Minimum consecutive successes for the readiness probe to be considered successful after having failed
deployment.readinessProbe.failureThreshold 2 Minimum consecutive failures for the readiness probe to be considered failed after having succeeded
deployment.strategy {} Allows one to configure the update strategy utilized by the deployment
deployment.terminationGracePeriodSeconds 30 Seconds that Kubernetes will wait for a pod to forcibly exit
enabled true Shell enable flag
extraContainers   List of extra containers to include
extraInitContainers   List of extra init containers to include
extraVolumeMounts   List of extra volumes mounts to do
extraVolumes   List of extra volumes to create
extraEnv   List of extra environment variables to expose
hpa.targetAverageValue 100m Set the autoscaling target value
image.pullPolicy IfNotPresent Shell image pull policy
image.pullSecrets   Secrets for the image repository
image.repository registry.com/gitlab-org/build/cng/gitlab-shell Shell image repository
image.tag master Shell image tag
init.image.repository   initContainer image
init.image.tag   initContainer image tag
logging.format text Set to json for JSON-structured logs
logging.sshdLogLevel ERROR Log level for underlying SSH daemon
replicaCount 1 Shell replicas
serviceLabels {} Supplemental service labels
service.externalTrafficPolicy Cluster Shell service external traffic policy (Cluster or Local)
service.internalPort 2222 Shell internal port
service.nodePort   Sets shell nodePort if set
service.name gitlab-shell Shell service name
service.type ClusterIP Shell service type
service.loadBalancerIP   IP address to assign to LoadBalancer (if supported)
service.loadBalancerSourceRanges   List of IP CIDRs allowed access to LoadBalancer (if supported)
securityContext.fsGroup 1000 Group ID under which the pod should be started
securityContext.runAsUser 1000 User ID under which the pod should be started
tolerations [] Toleration labels for pod assignment
workhorse.serviceName webservice Workhorse service name (by default, Workhorse is a part of the webservice Pods / Service)

Chart configuration examples

extraEnv

extraEnv allows you to expose additional environment variables in all containers in the pods.

Below is an example use of extraEnv: 

extraEnv:
  SOME_KEY: some_value
  SOME_OTHER_KEY: some_other_value

When the container is started, you can confirm that the environment variables are exposed: 

env | grep SOME
SOME_KEY=some_value
SOME_OTHER_KEY=some_other_value

image.pullSecrets

pullSecrets allows you to authenticate to a private registry to pull images for a pod.

Additional details about private registries and their authentication methods can be found in the Kubernetes documentation.

Below is an example use of pullSecrets: 

image:
  repository: my.shell.repository
  tag: latest
  pullPolicy: Always
  pullSecrets:
  - name: my-secret-name
  - name: my-secondary-secret-name

livenessProbe/readinessProbe

deployment.livenessProbe and deployment.readinessProbe provide a mechanism to help control the termination of Pods under some scenarios.

Larger repositories benefit from tuning liveness and readiness probe times to match their typical long-running connections. Set readiness probe duration shorter than liveness probe duration to minimize potential interruptions during clone and push operations. Increase terminationGracePeriodSeconds and give these operations more time before the scheduler terminates the pod. Consider the example below as a starting point to tune GitLab Shell pods for increased stability and efficiency with larger repository workloads. 

deployment:
  livenessProbe:
    initialDelaySeconds: 10
    periodSeconds: 20
    timeoutSeconds: 3
    successThreshold: 1
    failureThreshold: 10
  readinessProbe:
    initialDelaySeconds: 10
    periodSeconds: 5
    timeoutSeconds: 2
    successThreshold: 1
    failureThreshold: 3
  terminationGracePeriodSeconds: 300

Reference the official Kubernetes Documentation for additional details regarding this configuration.

tolerations

tolerations allow you schedule pods on tainted worker nodes

Below is an example use of tolerations: 

tolerations:
- key: "node_label"
  operator: "Equal"
  value: "true"
  effect: "NoSchedule"
- key: "node_label"
  operator: "Equal"
  value: "true"
  effect: "NoExecute"

annotations

annotations allows you to add annotations to the GitLab Shell pods.

Below is an example use of annotations 

annotations:
  kubernetes.io/example-annotation: annotation-value

External Services

This chart should be attached the Workhorse service.

Workhorse 

workhorse:
  host: workhorse.example.com
  serviceName: webservice
  port: 8181
Name Type Default Description
host String   The hostname of the Workhorse server. This can be omitted in lieu of serviceName.
port Integer 8181 The port on which to connect to the Workhorse server.
serviceName String webservice The name of the service which is operating the Workhorse server. By default, Workhorse is a part of the webservice Pods / Service. If this is present, and host is not, the chart will template the hostname of the service (and current .Release.Name) in place of the host value. This is convenient when using Workhorse as a part of the overall GitLab chart.

Chart Settings

The following values are used to configure the GitLab Shell Pods.

hostKeys.secret

The name of the Kubernetes secret to grab the SSH host keys from. The keys in the secret must start with the key names ssh_host_ in order to be used by GitLab Shell.

authToken

GitLab Shell uses an Auth Token in its communication with Workhorse. Share the token with GitLab Shell and Workhorse using a shared Secret. 

authToken:
 secret: gitlab-shell-secret
 key: secret
Name Type Default Description
authToken.key String   The name of the key in the above secret that contains the auth token.
authToken.secret String   The name of the Kubernetes Secret to pull from.

LoadBalancer Service

If the service.type is set to LoadBalancer, you can optionally specify service.loadBalancerIP to create the LoadBalancer with a user-specified IP (if your cloud provider supports it).

You can also optionally specify a list of service.loadBalancerSourceRanges to restrict the CIDR ranges that can access the LoadBalancer (if your cloud provider supports it).

Additional information about the LoadBalancer service type can be found in the Kubernetes documentation 

service:
  type: LoadBalancer
  loadBalancerIP: 1.2.3.4
  loadBalancerSourceRanges:
  - 5.6.7.8/32
  - 10.0.0.0/8

Configuring the networkpolicy

This section controls the NetworkPolicy. This configuration is optional and is used to limit Egress and Ingress of the Pods to specific endpoints.

Name Type Default Description
enabled Boolean false This setting enables the NetworkPolicy
ingress.enabled Boolean false When set to true, the Ingress network policy will be activated. This will block all Ingress connections unless rules are specified.
ingress.rules Array [] Rules for the Ingress policy, for details see https://kubernetes.io/docs/concepts/services-networking/network-policies/#the-networkpolicy-resource and the example below
egress.enabled Boolean false When set to true, the Egress network policy will be activated. This will block all egress connections unless rules are specified.
egress.rules Array [] Rules for the egress policy, these for details see https://kubernetes.io/docs/concepts/services-networking/network-policies/#the-networkpolicy-resource and the example below

Example Network Policy

The gitlab-shell service requires Ingress connections for port 22 and Egress connections to various to default workhorse port 8181. This examples adds the following network policy:

  • All Ingress requests from the network on TCP 0.0.0.0/0 port 2222 are allowed
  • All Egress requests to the network on UDP 10.0.0.0/8 port 53 are allowed for DNS
  • All Egress requests to the network on TCP 10.0.0.0/8 port 8181 are allowed for Workhorse
  • All Egress requests to the network on TCP 10.0.0.0/8 port 8075 are allowed for Gitaly

Note the example provided is only an example and may not be complete 

networkpolicy:
  enabled: true
  ingress:
    enabled: true
    rules:
      - to:
        - ipBlock:
            cidr: 0.0.0.0/0
        ports:
          - port: 2222
            protocol: TCP
  egress:
    enabled: true
    rules:
      - to:
        - ipBlock:
            cidr: 10.0.0.0/8
        ports:
          - port: 8181
            protocol: TCP
          - port: 8075
            protocol: TCP
          - port: 53
            protocol: UDP