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ZooKeeper

ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services. All of these kinds of services are used in some form or other by distributed applications.

Introduction

This chart bootstraps a ZooKeeper deployment on a Kubernetes cluster using the Helm package manager.

Prerequisites

  • Kubernetes 1.12+
  • Helm 3.0-beta3+
  • PV provisioner support in the underlying infrastructure

Installing the Chart

To install the chart with the release name my-zoo:

$ helm install my-zoo sconeapps/zookeeper

These commands deploy ZooKeeper on the Kubernetes cluster in the default configuration. The Parameters section lists the parameters that can be configured during installation.

List all releases using helm list

Uninstalling the Chart

To uninstall/delete the my-zoo deployment:

$ helm delete my-release

The command removes all the Kubernetes components associated with the chart and deletes the release.

Parameters

The following tables lists the configurable parameters of the ZooKeeper chart and their default values per section/component:

Parameter Description Default
global.imageRegistry Global Docker image registry nil
global.imagePullSecrets Global Docker registry secret names as an array [] (does not add image pull secrets to deployed pods)
global.storageClass Global storage class for dynamic provisioning nil

Common parameters

Parameter Description Default
nameOverride String to partially override zookeeper.fullname nil
fullnameOverride String to fully override zookeeper.fullname nil
clusterDomain Default Kubernetes cluster domain cluster.local
commonLabels Labels to add to all deployed objects {}
commonAnnotations Annotations to add to all deployed objects {}
schedulerName Kubernetes pod scheduler registry nil (use the default-scheduler)

Zookeeper chart parameters

Parameter Description Default
image.registry ZooKeeper image registry registry.scontain.com:5050
image.repository ZooKeeper Image name sconecuratedimages/apps
image.tag ZooKeeper Image tag {TAG_NAME}
image.pullPolicy ZooKeeper image pull policy IfNotPresent
image.pullSecrets Specify docker-registry secret names as an array [] (does not add image pull secrets to deployed pods)
image.debug Specify if debug values should be set false
tickTime Basic time unit in milliseconds used by ZooKeeper for heartbeats 2000
initLimit Time the ZooKeeper servers in quorum have to connect to a leader 10
syncLimit How far out of date a server can be from a leader 5
maxClientCnxns Number of concurrent connections that a single client may make to a single member 60
maxSessionTimeout Maximum session timeout in milliseconds that the server will allow the client to negotiate. 40000
autopurge.snapRetainCount Number of retains snapshots for autopurge 3
autopurge.purgeInterval The time interval in hours for which the purge task has to be triggered 0
fourlwCommandsWhitelist A list of comma separated Four Letter Words commands to use srvr, mntr
listenOnAllIPs Allow Zookeeper to listen for connections from its peers on all available IP addresses. false
allowAnonymousLogin Allow to accept connections from unauthenticated users yes
auth.existingSecret Use existing secret (ignores previous password) nil
auth.enabled Enable ZooKeeper auth false
auth.clientUser User that will use ZooKeeper clients to auth nil
auth.clientPassword Password that will use ZooKeeper clients to auth nil
auth.serverUsers List of user to be created nil
auth.serverPasswords List of passwords to assign to users when created nil
heapSize Size in MB for the Java Heap options (Xmx and XMs) []
logLevel Log level of ZooKeeper server ERROR
jvmFlags Default JVMFLAGS for the ZooKeeper process nil
config Configure ZooKeeper with a custom zoo.conf file nil
dataLogDir Data log directory ""
namespaceOverride Namespace for ZooKeeper resources. Overrides the release namespace. The Release Namespace

Statefulset parameters

Parameter Description Default
replicaCount Number of ZooKeeper nodes 1
updateStrategy Update strategy for the statefulset RollingUpdate
rollingUpdatePartition Partition update strategy nil
podManagementPolicy Pod management policy Parallel
podLabels ZooKeeper pod labels {} (evaluated as a template)
podAnnotations ZooKeeper Pod annotations {} (evaluated as a template)
affinity Affinity for pod assignment {} (evaluated as a template)
nodeSelector Node labels for pod assignment {} (evaluated as a template)
tolerations Tolerations for pod assignment [] (evaluated as a template)
priorityClassName Name of the existing priority class to be used by ZooKeeper pods ""
securityContext.enabled Enable security context (ZooKeeper master pod) true
securityContext.fsGroup Group ID for the container (ZooKeeper master pod) 1001
securityContext.runAsUser User ID for the container (ZooKeeper master pod) 1001
resources CPU/Memory resource requests/limits Memory: 256Mi, CPU: 250m
livenessProbe Liveness probe configuration for ZooKeeper Check values.yaml file
readinessProbe Readiness probe configuration for ZooKeeper Check values.yaml file
extraVolumes Extra volumes nil
extraVolumeMounts Mount extra volume(s) nil
podDisruptionBudget.maxUnavailable Max number of pods down simultaneously 1

Exposure parameters

Parameter Description Default
service.type Kubernetes Service type ClusterIP
service.loadBalancerIP Use with service.type LoadBalancer to assign static IP to Load Balancer instance ""
service.port ZooKeeper port 2181
service.followerPort ZooKeeper follower port 2888
service.electionPort ZooKeeper election port 3888
service.publishNotReadyAddresses If the ZooKeeper headless service should publish DNS records for not ready pods true
serviceAccount.create Enable creation of ServiceAccount for zookeeper pod false
serviceAccount.name The name of the service account to use. If not set and create is true, a name is generated Generated using the zookeeper.fullname template
service.tls.client_enable Enable tls for client connections false
service.tls.quorum_enable Enable tls for quorum protocol false
service.tls.disable_base_client_port Remove client port from service definitions. false
service.tls.client_port Service port for tls client connections 3181
service.tls.client_keystore_path KeyStore file path. Refer to extraVolumes amd extraVolumeMounts for mounting files into the pods /tls_key_store/key_store_file
service.tls.client_keystore_password KeyStore password. You can use environment variables. nil
service.tls.client_truststore_path TrustStore file path. Refer to extraVolumes amd extraVolumeMounts for mounting files into the pods /tls_trust_store/trust_store_file
service.tls.client_truststore_password TrustStore password. You can use environment variables. nil
service.tls.quorum_keystore_path KeyStore file path. Refer to extraVolumes amd extraVolumeMounts for mounting files into the pods /tls_key_store/key_store_file
service.tls.quorum_keystore_password KeyStore password. You can use environment variables. nil
service.tls.quorum_truststore_path TrustStore file path. Refer to extraVolumes amd extraVolumeMounts for mounting files into the pods /tls_trust_store/trust_store_file
service.tls.quorum_truststore_password TrustStore password. You can use environment variables. nil
service.annotations Annotations for the Service {}
service.headless.annotations Annotations for the Headless Service {}
networkPolicy.enabled Enable NetworkPolicy false
networkPolicy.allowExternal Don't require client label for connections true

Persistence parameters

Parameter Description Default
persistence.enabled Enable Zookeeper data persistence using PVC true
persistence.existingClaim Provide an existing PersistentVolumeClaim nil (evaluated as a template)
persistence.storageClass PVC Storage Class for ZooKeeper data volume nil
persistence.accessMode PVC Access Mode for ZooKeeper data volume ReadWriteOnce
persistence.size PVC Storage Request for ZooKeeper data volume 8Gi
persistence.annotations Annotations for the PVC {} (evaluated as a template)
persistence.dataLogDir.size PVC Storage Request for ZooKeeper's Data log directory 8Gi
persistence.dataLogDir.existingClaim Provide an existing PersistentVolumeClaim for Zookeeper's Data log directory nil (evaluated as a template)

Volume Permissions parameters

Parameter Description Default
volumePermissions.enabled Enable init container that changes the owner and group of the persistent volume(s) mountpoint to runAsUser:fsGroup false
volumePermissions.image.registry Init container volume-permissions image registry docker.io
volumePermissions.image.repository Init container volume-permissions image name minideb
volumePermissions.image.tag Init container volume-permissions image tag buster
volumePermissions.image.pullPolicy Init container volume-permissions image pull policy Always
volumePermissions.resources Init container resource requests/limit nil

Metrics parameters

Parameter Description Default
metrics.enabled Enable prometheus to access zookeeper metrics endpoint false
metrics.containerPort Port where a Jetty server will expose Prometheus metrics 9141
metrics.service.type Kubernetes service type (ClusterIP, NodePort or LoadBalancer) for Jetty server exposing Prometheus metrics ClusterIP
metrics.service.port Prometheus metrics service port 9141
metrics.service.annotations Service annotations for Prometheus to auto-discover the metrics endpoint {prometheus.io/scrape: "true", prometheus.io/port: "9141"}
metrics.serviceMonitor.enabled if true, creates a Prometheus Operator ServiceMonitor (also requires metrics.enabled to be true) false
metrics.serviceMonitor.namespace Namespace for the ServiceMonitor Resource The Release Namespace
metrics.serviceMonitor.interval Interval at which metrics should be scraped. nil (Prometheus Operator default value)
metrics.serviceMonitor.scrapeTimeout Timeout after which the scrape is ended nil (Prometheus Operator default value)
metrics.serviceMonitor.selector Prometheus instance selector labels nil
metrics.prometheusRule.enabled if true, creates a Prometheus Operator PrometheusRule (also requires metrics.enabled to be true and metrics.prometheusRule.rules) false
metrics.prometheusRule.namespace Namespace for the PrometheusRule Resource The Release Namespace
metrics.prometheusRule.selector Prometheus instance selector labels nil
metrics.prometheusRule.rules Prometheus Rule definitions (see values.yaml for examples) []

Specify each parameter using the --set key=value[,key=value] argument to helm install. For example,

$ helm install my-release \
  --set auth.clientUser=newUser \
    sconeapps/zookeeper

The above command sets the ZooKeeper user to newUser.

Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,

$ helm install my-release -f values.yaml sconeapps/zookeeper

One can use the default values.yaml in the SconeApps repo

Configuration and installation details

Rolling VS Immutable tags

It is strongly recommended to use immutable tags in a production environment. This ensures your deployment does not change automatically if the same tag is updated with a different image.

Production configuration

This chart includes a values-production.yaml file where you can find some parameters oriented to production configuration in comparison to the regular values.yaml. You can use this file instead of the default one.

  • Number of ZooKeeper nodes:
- replicaCount: 1
+ replicaCount: 3
  • Enable prometheus metrics:
- metrics.enabled: false
+ metrics.enabled: true

Log level

You can configure the ZooKeeper log level using the ZOO_LOG_LEVEL environment variable. By default, it is set to ERROR because of each readiness probe produce an INFO message on connection and a WARN message on disconnection.