ZooKeeper Configuration in KubeBlocks

This guide describes the two ZooKeeper configuration files managed by KubeBlocks and explains how each is handled.

Prerequisites

Before proceeding, verify your environment meets these requirements:

A functional Kubernetes cluster (v1.21+ recommended)
kubectl v1.21+ installed and configured with cluster access
Helm installed (installation guide)
KubeBlocks installed (installation guide)
ZooKeeper Add-on installed and a ZooKeeper cluster running (see Quickstart)

Configuration Files

KubeBlocks manages two ZooKeeper configuration files:

File	Type	How It Is Updated	Reload Behavior
`zoo.cfg`	Static	Rendered from addon template (read-only at runtime)	Requires pod restart
`zoo.cfg.dynamic`	Dynamic	Automatically updated by KubeBlocks during horizontal scaling	Hot reload

Dynamic Configuration (zoo.cfg.dynamic)

The zoo.cfg.dynamic file manages ZooKeeper ensemble membership — specifically the server.N entries that define which servers are in the ensemble.

KubeBlocks automatically maintains this file during horizontal scaling:

When you scale out, a new server.N entry is added
When you scale in, the leaving member's entry is removed

You do not need to modify zoo.cfg.dynamic manually.

WARNING

Only server.N entries are valid in zoo.cfg.dynamic.

Placing other parameters (e.g., syncLimit, tickTime) in this file will cause ZooKeeper to fail on startup with an Unrecognised parameter error.

Example of a valid zoo.cfg.dynamic for a 3-node ensemble:

server.0 = zookeeper-cluster-zookeeper-0.zookeeper-cluster-zookeeper-headless.demo.svc.cluster.local:2888:3888:participant
server.1 = zookeeper-cluster-zookeeper-1.zookeeper-cluster-zookeeper-headless.demo.svc.cluster.local:2888:3888:participant
server.2 = zookeeper-cluster-zookeeper-2.zookeeper-cluster-zookeeper-headless.demo.svc.cluster.local:2888:3888:participant

View the current dynamic configuration:


kubectl exec -n demo zookeeper-cluster-zookeeper-0 -- \
  cat /opt/bitnami/zookeeper/dynamic/zoo.cfg.dynamic

Static Configuration (zoo.cfg)

The zoo.cfg is rendered from the addon's ConfigMap template and contains the fixed cluster parameters:

Parameter	Value	Description
`tickTime`	2000	Basic time unit in milliseconds
`initLimit`	10	Ticks allowed for initial follower sync
`syncLimit`	30	Ticks allowed for follower-leader sync
`clientPort`	2181	Client connection port
`maxClientCnxns`	500	Max concurrent client connections per IP
`autopurge.snapRetainCount`	5	Number of snapshots to retain
`autopurge.purgeInterval`	12	Autopurge interval in hours
`metricsProvider.httpPort`	7000	Prometheus metrics port
`reconfigEnabled`	true	Enables ZooKeeper dynamic reconfiguration
`standaloneEnabled`	false	Required for ensemble mode

View the current static configuration:


kubectl exec -n demo zookeeper-cluster-zookeeper-0 -- \
  cat /opt/bitnami/zookeeper/conf/zoo.cfg

Example Output

tickTime=2000
initLimit=10
syncLimit=30
dataDir=/bitnami/zookeeper/data
dataLogDir=/bitnami/zookeeper/log
clientPort=2181
maxClientCnxns=500
autopurge.snapRetainCount=5
autopurge.purgeInterval=12
metricsProvider.className=org.apache.zookeeper.metrics.prometheus.PrometheusMetricsProvider
metricsProvider.httpPort=7000
metricsProvider.exportJvmInfo=true
4lw.commands.whitelist=srvr, mntr, ruok, conf, stat, sync
standaloneEnabled=false
reconfigEnabled=true
dynamicConfigFile=/opt/bitnami/zookeeper/dynamic/zoo.cfg.dynamic
audit.enable=true

NOTE

Static parameters in zoo.cfg are rendered from the addon template at cluster creation time. The current version of the ZooKeeper addon does not expose these as user-configurable parameters through the KubeBlocks API. If you need to customize static parameters, consider opening an issue or contributing to the kubeblocks-addons repository.

Cleanup

kubectl delete cluster zookeeper-cluster -n demo
kubectl delete ns demo