ClickHouse Operator configuration guide - ClickHouse Documentation

This guide covers how to configure ClickHouse and Keeper clusters using the operator.

ClickHouseCluster configuration

Basic configuration

apiVersion: clickhouse.com/v1alpha1
kind: ClickHouseCluster
metadata:
  name: my-cluster
spec:
  replicas: 3           # Number of replicas per shard
  shards: 2             # Number of shards
  keeperClusterRef:
    name: my-keeper     # Reference to KeeperCluster
  dataVolumeClaimSpec:
    resources:
      requests:
        storage: 10Gi

Replicas and shards

Replicas: Number of ClickHouse instances per shard (for high availability)
Shards: Number of horizontal partitions (for scaling)

spec:
  replicas: 3  # Default: 3
  shards: 2    # Default: 1

A cluster with replicas: 3 and shards: 2 will create 6 ClickHouse pods total.

Keeper integration

Every ClickHouse cluster must reference a KeeperCluster for coordination:

spec:
  keeperClusterRef:
    name: my-keeper
    # namespace: keeper-system  # Optional, defaults to the ClickHouseCluster namespace

When keeperClusterRef.namespace is set, the operator must watch both namespaces. If WATCH_NAMESPACE is configured, include the ClickHouse and Keeper namespaces in that list.

KeeperCluster configuration

apiVersion: clickhouse.com/v1alpha1
kind: KeeperCluster
metadata:
  name: my-keeper
spec:
  replicas: 3  # Must be odd: 1, 3, 5, 7, 9, 11, 13, or 15
  dataVolumeClaimSpec:
    resources:
      requests:
        storage: 5Gi

Storage configuration

Configure persistent storage with dataVolumeClaimSpec, a standard Kubernetes PersistentVolumeClaimSpec. The operator turns it into a per-replica PersistentVolumeClaim mounted at the data path /var/lib/clickhouse:

spec:
  dataVolumeClaimSpec:
    storageClassName: fast-ssd  # Optional: consider your storage class based on the installed CSI
    resources:
      requests:
        storage: 100Gi

The operator can modify an existing PVC only if the underlying StorageClass supports volume expansion.

Attaching extra disks in a multi-disk (JBOD) layout, running without a persistent volume, expanding capacity, custom storage policies, and the rules for what cannot change after creation are covered in the dedicated Storage and volumes guide.

Cluster domain

spec.clusterDomain sets the Kubernetes DNS suffix the operator uses when it builds the fully-qualified pod host names it writes into the ClickHouse server configuration. It defaults to cluster.local and exists on both ClickHouseCluster and KeeperCluster.

spec:
  clusterDomain: cluster.local   # default; override only for a custom domain

The operator addresses every pod through the headless Service as <pod>.<headless-service>.<namespace>.svc.<clusterDomain>. That suffix flows into two parts of the generated configuration:

On a ClickHouseCluster, its value is used for the replica host names in remote_servers (cross-replica and Distributed queries).
On a KeeperCluster, its value builds the Keeper node host names that ClickHouse uses for coordination.

Only override this when your cluster’s kubelet runs with a --cluster-domain other than cluster.local. If the value does not match the real cluster domain, ClickHouse cannot resolve the Keeper and replica host names — coordination and Distributed queries fail with DNS resolution errors. Set the same value on the ClickHouseCluster and the KeeperCluster it references.

Multi-disk (JBOD) storage

additionalVolumeClaimTemplates attaches extra disks to each ClickHouse replica, on top of the primary dataVolumeClaimSpec, which is required to use them. Each entry is a PVC template — a metadata.name plus a PVC spec. The disks are reconciled exactly like the primary data disk — as StatefulSet volumeClaimTemplates — so the StatefulSet controller creates and retains one PVC per replica, named <name>-<statefulset>-0.

spec:
  dataVolumeClaimSpec:
    storageClassName: fast-ssd
    resources:
      requests:
        storage: 100Gi
  additionalVolumeClaimTemplates:
    - metadata:
        name: disk1
      spec:
        storageClassName: fast-ssd
        resources:
          requests:
            storage: 100Gi
    - metadata:
        name: disk2
      spec:
        storageClassName: fast-ssd
        resources:
          requests:
            storage: 100Gi

The operator mounts each additional volume at /var/lib/clickhouse/disks/<name> and adds it to a generated ClickHouse storage configuration. Hyphens in a name become underscores in the ClickHouse disk identifier; the mount path keeps the original name. The primary data disk and every additional disk are placed in a single volume of the default storage policy, so ClickHouse spreads new data parts across all of them in round-robin fashion. Usable capacity is the sum of all disks, and every table that does not set its own storage_policy (including system.* tables) uses the combined set.

PVC names must match ^[a-z]([-a-z0-9]*[a-z0-9])?$ and must not collide with the primary data volume name. Like the primary data disk, the set of additional disks is fixed at creation: adding, removing, or renaming entries after creation is rejected. Additional PVCs are retained when the cluster is deleted, like the primary data disk. Storage size on an existing entry can be expanded if the StorageClass supports expansion.

Cluster domain

spec:
  clusterDomain: cluster.local   # default; override only for a custom domain

The operator addresses every pod through the headless Service as <pod>.<headless-service>.<namespace>.svc.<clusterDomain>. That suffix flows into two parts of the generated configuration:

On a ClickHouseCluster, its value is used for the replica host names in remote_servers (cross-replica and Distributed queries).
On a KeeperCluster, its value builds the Keeper node host names that ClickHouse uses for coordination.

Pod configuration

Automatic topology spread and affinity

Distribute pods across availability zones:

spec:
  podTemplate:
    topologyZoneKey: topology.kubernetes.io/zone
    nodeHostnameKey: kubernetes.io/hostname

Ensure your Kubernetes cluster has enough nodes in different zones to satisfy the spread constraints.

Manual configuration

Arbitrary pod affinity/anti-affinity rules and topology spread constraints can be specified.

spec:
  podTemplate:
    affinity:
      <your-affinity-rules-here>
    topologySpreadConstraints:
      <your-topology-spread-constraints-here>

See API Reference for all supported Pod template options.

Pod disruption budgets

The operator creates a PodDisruptionBudget (PDB) for each cluster so that voluntary disruptions — node drains, rolling upgrades, autoscaler evictions — cannot take down enough pods to lose quorum or break availability. For ClickHouse clusters with more than one shard, one PDB is created per shard so a disruption in one shard cannot count against another.

Defaults

The operator picks safe defaults based on the cluster size so that a fresh apply already protects against accidental quorum loss.

Resource	Topology	Default PDB
`ClickHouseCluster`	`replicas: 1` (single-replica shard)	`maxUnavailable: 1` — disruption is allowed for a single-node cluster so that node drains are not blocked
`ClickHouseCluster`	`replicas: 2+` (multi-replica shard)	`minAvailable: 1` — at least one replica per shard must stay up
`KeeperCluster`	`replicas: 1`	`maxUnavailable: 1` — disruption is allowed for a single-node cluster so that node drains are not blocked
`KeeperCluster`	`replicas: 3+`	`maxUnavailable: replicas/2` — preserves the RAFT quorum for a `2F+1` cluster (3 replicas tolerate 1 down, 5 replicas tolerate 2 down)

For a 3-shard ClickHouseCluster with replicas: 3, the operator creates three PDBs, one per shard, each with minAvailable: 1.

Overriding the defaults

Use spec.podDisruptionBudget to override either minAvailable or maxUnavailable (exactly one):

spec:
  replicas: 3
  shards: 2
  podDisruptionBudget:
    minAvailable: 2   # keep at least 2 of 3 replicas in every shard up during a disruption

Or the maxUnavailable form, with a percentage:

spec:
  replicas: 5
  podDisruptionBudget:
    maxUnavailable: 40%

Setting both minAvailable and maxUnavailable is rejected by the validating webhook. Pick one — Kubernetes itself does not allow both either.

You can also pass the unhealthyPodEvictionPolicy field through to the generated PDB — useful when you need to allow eviction of pods that are still in NotReady:

spec:
  podDisruptionBudget:
    minAvailable: 2
    unhealthyPodEvictionPolicy: AlwaysAllow

Policies

spec.podDisruptionBudget.policy lets you choose how aggressively the operator manages PDBs:

Policy	Behavior
`Enabled` (default)	The operator creates and updates the PDB on every reconcile. This is the safe production default.
`Disabled`	The operator does not create PDBs and deletes any existing ones with matching labels. Useful for development clusters where every voluntary disruption should be allowed.
`Ignored`	The operator neither creates nor deletes PDBs. Existing PDBs are left alone. Use this when another system (e.g. policy admission, GitOps tool) owns PDB management for you.

Example — disable PDB management completely on a development cluster:

spec:
  podDisruptionBudget:
    policy: Disabled

Example — keep your hand-crafted PDB next to the cluster and stop the operator from touching it:

spec:
  podDisruptionBudget:
    policy: Ignored

Cluster-wide opt-out

PDB management can also be disabled cluster-wide via the operator’s ENABLE_PDB environment variable. With ENABLE_PDB=false, the operator skips the PDB reconcile step for every ClickHouseCluster and KeeperCluster regardless of their spec.podDisruptionBudget.policy, and does not watch PodDisruptionBudget resources at all. The operator’s ServiceAccount therefore does not need RBAC permissions on poddisruptionbudgets.policy/v1, which is useful when running the operator under a restricted ServiceAccount that intentionally omits those permissions.

# in the operator Deployment spec
env:
- name: ENABLE_PDB
  value: "false"

This is intended for environments that ship their own disruption policies (e.g. through Gatekeeper / Kyverno) and want the operator out of the loop entirely.

Container configuration

Custom image

Use a specific ClickHouse image:

spec:
  containerTemplate:
    image:
      repository: clickhouse/clickhouse-server
      tag: "25.12"
    imagePullPolicy: IfNotPresent

Container resources

Configure CPU and memory for ClickHouse containers:

# default values
spec:
  containerTemplate:
    resources:
      requests:
        cpu: "250m"
        memory: "512Mi"
      limits:
        cpu: "1"
        memory: "512Mi"

Environment variables

Add custom environment variables:

spec:
  containerTemplate:
    env:
    - name: CUSTOM_ENV_VAR
      value: "1"

Volume mounts

Add additional volume mounts:

spec:
  containerTemplate:
    volumeMounts:
    - name: custom-config
      mountPath: /etc/clickhouse-server/config.d/custom.xml
      subPath: custom.xml

It is allowed to specify multiple volume mounts to the same mountPath. Operator will create projected volume with all specified mounts.

See API Reference for all supported Container template options.

TLS/SSL configuration

Configure secure endpoints

Pass a reference to a Kubernetes Secret containing TLS certificates to enable secure endpoints

spec:
  settings:
    tls:
      enabled: true
      required: true # Insecure ports are disabled if set
      serverCertSecret:
        name: <certificate-secret-name>

SSL certificate secret format

It is expected that the Secret contains the server keypair:

tls.crt - PEM encoded server certificate
tls.key - PEM encoded private key

This format is compatible with cert-manager generated certificates.

ClickHouse-Keeper communication over TLS

If KeeperCluster has TLS enabled, ClickHouseCluster would use secure connection to Keeper nodes automatically. ClickHouseCluster verifies Keeper node certificates against the system trust store, plus any caBundle you configure. To trust a private CA (for example, a self-signed or internal CA), provide a custom CA bundle reference:

spec:
    settings:
        tls:
          caBundle:
            name: <ca-certificate-secret-name>
            key: <ca-certificate-key>

External Secret

By default the operator creates and owns a Secret containing the cluster’s internal credentials (interserver password, management password, keeper identity, cluster secret, named-collections key). The Secret is named after the cluster and lives in the cluster’s namespace. If you want to manage these credentials yourself — for example, sourcing them from HashiCorp Vault, AWS Secrets Manager, or External Secrets Operator — point the operator at a pre-existing Secret using spec.externalSecret:

apiVersion: clickhouse.com/v1alpha1
kind: ClickHouseCluster
metadata:
  name: sample
spec:
  replicas: 2
  keeperClusterRef:
    name: sample
  dataVolumeClaimSpec:
    resources:
      requests:
        storage: 10Gi
  externalSecret:
    name: my-clickhouse-credentials
    policy: Observe

The referenced Secret must reside in the same namespace as the ClickHouseCluster. The operator never deletes a Secret it did not create.

Required keys

The Secret must contain the following keys:

Key	Format	When required
`interserver-password`	plaintext password	Always
`management-password`	plaintext password	Always
`keeper-identity`	`clickhouse:<password>`	Always
`cluster-secret`	plaintext password	Always
`named-collections-key`	hex-encoded 16-byte AES key (32 hex chars)	ClickHouse `>= 25.12` only

A complete Secret looks like this:

apiVersion: v1
kind: Secret
metadata:
  name: my-clickhouse-credentials
  namespace: sample
type: Opaque
stringData:
  interserver-password: "a-strong-random-password"
  management-password: "another-strong-password"
  keeper-identity: "clickhouse:keeper-auth-password"
  cluster-secret: "cluster-internal-secret"
  named-collections-key: "0123456789abcdef0123456789abcdef"   # 32 hex chars = 16 bytes

Policy: Observe vs Manage

spec.externalSecret.policy controls how the operator handles missing required keys:

Policy	Behavior on missing keys
`Observe` (default)	Reconciliation is blocked until every required key is present. The operator reports each missing key — and the format hint for it — via the `ExternalSecretValid` condition (with reason `ExternalSecretInvalid`) and a `Warning` event.
`Manage`	The operator generates any missing required keys and writes them back to the same Secret. Useful for bootstrapping: create an empty Secret, let the operator fill it, then optionally tighten access. The operator still never deletes the Secret.

Even with policy: Manage the Secret must already exist in the namespace — the operator never creates the Secret itself, it only writes generated keys into an existing one. If the referenced Secret is missing, reconciliation is blocked with the ExternalSecretNotFound reason regardless of policy.

Pick Observe when an external system (Vault, ESO, sealed-secrets, GitOps) is the source of truth and you want the operator to fail loudly on misconfiguration. Pick Manage when you want self-sufficient bootstrapping but still want to retain ownership of the Secret object itself (for example, to back it up).

Status condition and troubleshooting

The operator exposes a ExternalSecretValid condition on ClickHouseCluster.status.conditions. Inspect it when reconciliation looks stuck:

# Plain kubectl — works out of the box
kubectl describe clickhousecluster sample | sed -n '/Conditions:/,$p'

# Same data as YAML
kubectl get clickhousecluster sample -o yaml | sed -n '/conditions:/,/^[^ ]/p'

# Pretty-printed JSON (requires jq)
kubectl get clickhousecluster sample -o jsonpath='{.status.conditions}' | jq

Possible reasons:

`reason`	Meaning	Fix
`ExternalSecretNotFound`	The referenced Secret does not exist in the namespace.	Create the Secret, or fix `spec.externalSecret.name`.
`ExternalSecretInvalid`	The Secret exists but lacks required keys (only with `Observe`). The message lists each missing key together with its expected format.	Add the missing keys, or switch to `policy: Manage`.
`ExternalSecretValid`	All required keys are present and the operator is using the Secret.	—

The operator requeues reconciliation while the Secret is invalid, so once you add the missing keys the next reconcile picks them up automatically — no need to bounce pods.

The set of required keys depends on the running ClickHouse version. named-collections-key is only validated once the operator’s version probe has detected ClickHouse 25.12 or newer. On older versions the key may be absent from the Secret.

Additional ports

The operator exposes a fixed set of ports on every ClickHouse Pod and its headless Service: 8123 HTTP, 9000 native, 9009 interserver, 9001 management, 9363 Prometheus metrics, and the TLS variants 8443/9440 when TLS is enabled. To make ClickHouse listen on additional protocols — MySQL, PostgreSQL, gRPC, or any custom port — declare them in spec.additionalPorts:

spec:
  additionalPorts:
    - name: mysql
      port: 9004
    - name: postgres
      port: 9005
    - name: grpc
      port: 9100

The operator adds those ports to the Pod’s containerPorts and to the headless Service. The complete example lives at examples/custom_protocols.yaml.

additionalPorts only opens the ports on the Kubernetes side. It does not configure the ClickHouse server to listen on them. You also have to enable the matching protocol in spec.settings.extraConfig.protocols. Without that, the port is open on the Service but nothing inside the pod is answering.

End-to-end example: MySQL wire protocol

To expose ClickHouse over the MySQL wire protocol on port 9004:

apiVersion: clickhouse.com/v1alpha1
kind: ClickHouseCluster
metadata:
  name: sample
spec:
  replicas: 1
  keeperClusterRef:
    name: sample
  dataVolumeClaimSpec:
    resources:
      requests:
        storage: 2Gi

  # 1) Open the port on the Pod and the headless Service.
  additionalPorts:
    - name: mysql
      port: 9004

  # 2) Tell ClickHouse server to actually listen on it.
  settings:
    extraConfig:
      protocols:
        mysql:
          type: mysql
          port: 9004
          description: "MySQL wire protocol"

After applying, verify from inside the cluster:

kubectl exec sample-clickhouse-0-0-0 -- \
  clickhouse-client --port 9004 --query "SELECT 1"

Field constraints

Field	Rule
`name`	Must match the DNS_LABEL pattern `^[a-z]([-a-z0-9]*[a-z0-9])?$`, max 63 characters. Uniqueness is enforced by the CRD as a list-map key.
`port`	Integer in `[1, 65535]`. The webhook rejects duplicate port numbers within the list.

Reserved ports and names

The validating webhook rejects additionalPorts entries that would collide with ports the operator binds itself. All TLS-related ports are reserved unconditionally so that flipping spec.settings.tls.enabled later cannot break a previously valid cluster.

Port	Reserved for
`8123`	HTTP
`8443`	HTTPS
`9000`	native TCP
`9440`	native TLS
`9009`	interserver
`9001`	management
`9363`	Prometheus metrics

The following names are also rejected — they are the operator’s internal protocol-type identifiers (not the human-readable aliases):

Name
`http`
`http-secure`
`tcp`
`tcp-secure`
`interserver`
`management`
`prometheus`

A rejected request produces an error such as:

spec.additionalPorts[0].port: 8123 is reserved for the operator-managed HTTP port
spec.additionalPorts[0].name: "http" is reserved by the operator

Version probe and upgrade channel

The operator does two independent things with cluster versions:

Version reporting — for ClickHouseCluster, a Kubernetes Job runs the container image once to detect the running ClickHouse version; for KeeperCluster, the operator reads the server-reported version from running replicas. The detected version is recorded in .status.version and used by other reconciliation steps (e.g. the External Secret named-collections key is only required from ClickHouse 25.12).
Upgrade channel — a periodic check against the public ClickHouse release feed (https://clickhouse.com/data/version_date.tsv). The operator reports whether a newer version is available via the VersionUpgraded status condition. It never upgrades the cluster on its own — the user is in control of the image tag.

Choosing a release channel

spec.upgradeChannel selects which set of upstream releases the operator compares against. Same field exists on both ClickHouseCluster and KeeperCluster.

spec:
  upgradeChannel: lts   # or "stable", or "25.8", or omitted

Allowed values (validated by the CRD with the pattern ^(lts|stable|\d+\.\d+)?$):

Value	Behavior
empty (default)	The operator proposes only minor updates within the currently-running major.minor line. A cluster on `25.8.3.1` will be told about `25.8.4.x` but not `25.9.x`.
`stable`	Tracks the upstream `stable` channel — the latest release that ClickHouse Inc. flags as stable on the main release line. Receives major upgrades sooner than the `lts` channel.
`lts`	Tracks the upstream `lts` channel — long-term support releases. Receives major upgrades less frequently, with longer support windows.
`25.8` (or any `<major>.<minor>`)	Pins the channel to a specific major.minor line. Major upgrades beyond it are not proposed even if a newer version exists upstream.

For production, pinning the channel to an explicit <major>.<minor> (e.g. 25.8) is generally preferred. It locks the cluster to the intended major release line and lets the operator surface a WrongReleaseChannel warning if any replica somehow drifts onto a different major — which matters especially when the image is referenced by a digest (@sha256:...) rather than by a human-readable tag. The empty default is fine for development clusters where major-version jumps are not a concern.

Status conditions

Two conditions surface the result of the probe and the upgrade check:

Condition	Reason	Meaning
`VersionInSync`	`VersionMatch`	All replicas report the same version
`VersionInSync`	`VersionMismatch`	Replicas are running different versions. This reason is suppressed during a planned rolling upgrade. It typically surfaces when a mutable image tag has been pinned (for example `latest` or a bare major like `26.3`) and the underlying registry has shifted between pulls, so different replicas ended up on different patches of the same tag.
`VersionInSync`	`VersionPending`	Version probe Job has not finished yet, or no Keeper replica version has been observed yet
`VersionInSync`	`VersionProbeFailed`	ClickHouse probe Job failed; the operator cannot determine the running version
`VersionUpgraded`	`UpToDate`	The cluster is on the latest version available in the selected channel
`VersionUpgraded`	`MinorUpdateAvailable`	A newer patch is available in the same `major.minor` line
`VersionUpgraded`	`MajorUpdateAvailable`	A newer `major.minor` is available within the chosen channel
`VersionUpgraded`	`VersionOutdated`	The running version is out of date and will no longer receive fixes from the selected channel — typically because the major line has been dropped from `lts` or `stable` upstream
`VersionUpgraded`	`WrongReleaseChannel`	The running image does not belong to the selected `upgradeChannel`. Example: a cluster running `26.5` with `upgradeChannel: lts`, since `26.5` is not part of the upstream `lts` line.
`VersionUpgraded`	`UpgradeCheckFailed`	The operator could not reach the upstream release feed

Inspect them with:

kubectl get clickhousecluster sample -o yaml | sed -n '/conditions:/,/^[^ ]/p'

Overriding the version probe Job

This applies to ClickHouseCluster only. KeeperCluster no longer runs a version-probe Job — its version is read directly from the running Keeper replicas — so spec.versionProbeTemplate is deprecated and has no effect there. The probe is implemented as a regular Kubernetes Job. If your cluster has admission policies that require specific Tolerations, node selectors, security contexts, or you want to limit how long completed probe Jobs linger, override the template via spec.versionProbeTemplate:

spec:
  versionProbeTemplate:
    spec:
      ttlSecondsAfterFinished: 600   # delete completed probe Jobs 10 minutes after completion
      template:
        spec:
          nodeSelector:
            kubernetes.io/arch: amd64
          tolerations:
            - key: dedicated
              operator: Equal
              value: clickhouse
              effect: NoSchedule
          containers:
            - name: version-probe
              resources:
                requests:
                  cpu: 50m
                  memory: 64Mi

The container name version-probe is the operator’s default — the entry under containers: matches it by name, so the operator deep-merges the user-provided fields on top of the defaults.

Operator-wide controls

Two flags on the operator manager control the upgrade-check loop globally:

Flag	Default	Effect
`--version-update-interval`	`24h`	How often the operator re-fetches the upstream version list
`--disable-version-update-checks`	`false`	Disables the upgrade checker entirely. The `VersionUpgraded` condition is not set, and no outbound HTTP traffic to `clickhouse.com` is generated

Set --disable-version-update-checks=true in air-gapped environments or when egress to clickhouse.com is not allowed.

ClickHouse settings

Default user password

spec.settings.defaultUserPassword sets the password for the built-in default user. Provide the value from a key in a Secret (recommended) or a ConfigMap that you create, rather than inline in the CR:

spec:
  settings:
    defaultUserPassword:
      passwordType: password   # default; see "Password types" below
      secret:                  # exactly one of secret or configMap
        name: clickhouse-password   # name of the Secret/ConfigMap
        key: password               # the key inside it, not the password value

Provide exactly one of secret or configMap, each with both name (the object) and key (the entry that holds the password).

Password types

passwordType tells ClickHouse how to interpret the value. It defaults to password (plaintext); the alternatives are hashed forms such as password_sha256_hex and password_double_sha1_hex. Prefer a hashed type so the plaintext is never stored. See the ClickHouse user settings for the full list.

Full example with a Secret

Create the Secret, then reference its key:

kubectl create secret generic clickhouse-password \
  --from-literal=password='your-secure-password'

apiVersion: clickhouse.com/v1alpha1
kind: ClickHouseCluster
metadata:
  name: my-cluster
spec:
  settings:
    defaultUserPassword:
      passwordType: password
      secret:
        name: clickhouse-password
        key: password

With passwordType: password, the in-pod clickhouse-client is configured with this password, which is handy for debugging.

For a hashed password, store the hash instead of the plaintext:

echo -n 'your-secure-password' | sha256sum   # use the hex digest as the value
kubectl create secret generic clickhouse-password \
  --from-literal=password='<sha256-hex-digest>'

spec:
  settings:
    defaultUserPassword:
      passwordType: password_sha256_hex
      secret:
        name: clickhouse-password
        key: password

Using a ConfigMap

A ConfigMap works the same way, but its contents are not protected like a Secret. Use it only for non-sensitive or already-hashed values, such as a password_sha256_hex digest:

spec:
  settings:
    defaultUserPassword:
      passwordType: password_sha256_hex
      configMap:
        name: clickhouse-config
        key: default_password

Do not put a plaintext password in a ConfigMap. Use a Secret for any plaintext (passwordType: password) value.

Custom users in configuration

Configure additional users in configuration files. Create a ConfigMap and Secret for user:

apiVersion: v1
kind: ConfigMap
metadata:
  name: user-config
data:
  reader.yaml: |
    users:
      reader:
        password:
          - '@from_env': READER_PASSWORD
        profile: default
        grants:
          - query: "GRANT SELECT ON *.*"
---
apiVersion: v1
kind: Secret
metadata:
  name: reader-password
data:
  password: "c2VjcmV0LXBhc3N3b3Jk"  # base64("secret-password")

Add custom configuration to ClickHouseCluster:

spec:
  podTemplate:
    volumes:
      - name: reader-user
        configMap:
          name: user-config
  containerTemplate:
    env:
      - name: READER_PASSWORD
        valueFrom:
          secretKeyRef:
            name: reader-password
            key: password
    volumeMounts:
      - mountPath: /etc/clickhouse-server/users.d/
        name: reader-user
        readOnly: true

Database sync

Enable automatic database synchronization for new replicas:

spec:
  settings:
    enableDatabaseSync: true  # Default: true

When enabled, the operator synchronizes Replicated and integration tables to new replicas.

Server logging

Configure the ClickHouse server log through spec.settings.logger. Every field is optional with a safe default, so a cluster you never touch already logs at trace to both the container console and a rotated file on disk.

spec:
  settings:
    logger:
      logToFile: true   # Default: true. Set false to log only to the console
      jsonLogs: false   # Default: false. Set true for structured JSON log lines
      level: trace      # Default: trace
      size: 1000M       # Default: 1000M. Rotate a log file once it reaches this size
      count: 50         # Default: 50. Number of rotated files to keep

Field	Default	Description
`logToFile`	`true`	When `false`, the operator drops the file targets and the server logs only to the container console.
`jsonLogs`	`false`	When `true`, the operator adds `formatting.type: json` so each line is a JSON object.
`level`	`trace`	Log verbosity. One of `test`, `trace`, `debug`, `information`, `notice`, `warning`, `error`, `critical`, `fatal`.
`size`	`1000M`	Maximum size of a single log file before rotation.
`count`	`50`	Number of rotated log files the server retains.

The operator always keeps console logging on so that kubectl logs works, and layers file logging on top when logToFile is true. A cluster with the defaults renders this logger block:

logger:
  console: true
  level: trace
  log: /var/log/clickhouse-server/clickhouse-server.log
  errorlog: /var/log/clickhouse-server/clickhouse-server.err.log
  size: 1000M
  count: 50

The same spec.settings.logger block applies to a KeeperCluster; the operator writes its files under /var/log/clickhouse-keeper/ instead.

Console logging stays on regardless of logToFile, so kubectl logs keeps working even when you disable file logging. Set jsonLogs: true when you ship logs to a structured log store that parses JSON.

Custom configuration

Embedded extra configuration

Instead of mounting custom configuration files, you can directly specify additional ClickHouse configuration options. Add custom ClickHouse configuration using extraConfig:

spec:
  settings:
    extraConfig:
      background_pool_size: 20

Useful links:

Embedded extra users configuration

You can also specify additional ClickHouse users configuration using extraUsersConfig. This is useful for defining users, profiles, quotas, and grants directly in the cluster specification.

spec:
  settings:
    extraUsersConfig:
      users:
        analyst:
          password:
            - '@from_env': ANALYST_PASSWORD
          profile: "readonly"
          quota: "default"
      profiles:
        readonly:
          readonly: 1
          max_memory_usage: 10000000000
      quotas:
        default:
          interval:
            duration: 3600
            queries: 1000
            errors: 100

The extraUsersConfig is stored in k8s ConfigMap object. Avoid plain text secrets there.

See documentation for all supported ClickHouse users configuration options.

Configuration example

Complete configuration example:

apiVersion: clickhouse.com/v1alpha1
kind: KeeperCluster
metadata:
  name: sample
spec:
  replicas: 3
  dataVolumeClaimSpec:
    storageClassName: <storage-class-name>
    resources:
      requests:
        storage: 10Gi
  podTemplate:
    topologyZoneKey: topology.kubernetes.io/zone
    nodeHostnameKey: kubernetes.io/hostname
  containerTemplate:
    resources:
      requests:
        cpu: "2"
        memory: "4Gi"
      limits:
        cpu: "4"
        memory: "8Gi"
  settings:
    tls:
      enabled: true
      required: true
      serverCertSecret:
        name: <keeper-certificate-secret>
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: default-user-password
data:
  # secret-password
  password: "..." # sha256 hex of the password
---
apiVersion: clickhouse.com/v1alpha1
kind: ClickHouseCluster
metadata:
  name: sample
spec:
  replicas: 2
  dataVolumeClaimSpec:
    storageClassName: <storage-class-name>
    resources:
      requests:
        storage: 200Gi
  keeperClusterRef:
    name: sample
  podTemplate:
    topologyZoneKey: topology.kubernetes.io/zone
    nodeHostnameKey: kubernetes.io/hostname
  settings:
    tls:
      enabled: true
      required: true
      serverCertSecret:
        name: clickhouse-cert
    defaultUserPassword:
      passwordType: password_sha256_hex
      configMap:
        key: password
        name: default-password

​ClickHouseCluster configuration

​Basic configuration

​Replicas and shards

​Keeper integration

​KeeperCluster configuration

​Storage configuration

​Cluster domain

​Multi-disk (JBOD) storage

​Cluster domain

​Pod configuration

​Automatic topology spread and affinity

​Manual configuration

​See API Reference for all supported Pod template options.

​Pod disruption budgets

​Defaults

​Overriding the defaults

​Policies

​Cluster-wide opt-out

​Container configuration

​Custom image

​Container resources

​Environment variables

​Volume mounts

​See API Reference for all supported Container template options.

​TLS/SSL configuration

​Configure secure endpoints

​SSL certificate secret format

​ClickHouse-Keeper communication over TLS

​External Secret

​Required keys

​Policy: Observe vs Manage

​Status condition and troubleshooting

​Additional ports

​End-to-end example: MySQL wire protocol

​Field constraints

​Reserved ports and names

​Version probe and upgrade channel

​Choosing a release channel

​Status conditions

​Overriding the version probe Job

​Operator-wide controls

​ClickHouse settings

​Default user password

​Password types

​Full example with a Secret

​Using a ConfigMap

​Custom users in configuration

​Database sync

​Server logging

​Custom configuration

​Embedded extra configuration

​Useful links:

​Embedded extra users configuration

​See documentation for all supported ClickHouse users configuration options.

​Configuration example

ClickHouseCluster configuration

Basic configuration

Replicas and shards

Keeper integration

KeeperCluster configuration

Storage configuration

Cluster domain

Multi-disk (JBOD) storage

Cluster domain

Pod configuration

Automatic topology spread and affinity

Manual configuration

See API Reference for all supported Pod template options.

Pod disruption budgets

Defaults

Overriding the defaults

Policies

Cluster-wide opt-out

Container configuration

Custom image

Container resources

Environment variables

Volume mounts

See API Reference for all supported Container template options.

TLS/SSL configuration

Configure secure endpoints

SSL certificate secret format

ClickHouse-Keeper communication over TLS

External Secret

Required keys

Policy: Observe vs Manage

Status condition and troubleshooting

Additional ports

End-to-end example: MySQL wire protocol

Field constraints

Reserved ports and names

Version probe and upgrade channel

Choosing a release channel

Status conditions

Overriding the version probe Job

Operator-wide controls

ClickHouse settings

Default user password

Password types

Full example with a Secret

Using a ConfigMap

Custom users in configuration

Database sync

Server logging

Custom configuration

Embedded extra configuration

Useful links:

Embedded extra users configuration

See documentation for all supported ClickHouse users configuration options.

Configuration example