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`
`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.