Reconfigure ClickHouse Parameters

KubeBlocks supports dynamic reconfiguration of ClickHouse server parameters. Changes are applied without restarting pods for parameters that support live reload.

Prerequisites

A functional Kubernetes cluster (v1.21+ recommended)
kubectl v1.21+ installed and configured with cluster access
KubeBlocks installed (installation guide)
ClickHouse Add-on enabled
A demo namespace: kubectl create ns demo

Update a ClickHouse Parameter

The following example updates clickhouse.profiles.web.max_bytes_to_read, which limits the maximum bytes read per query for the web profile:


kubectl apply -f - <<EOF
apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: ch-reconfiguring
  namespace: demo
spec:
  clusterName: clickhouse-cluster
  type: Reconfiguring
  reconfigures:
    - componentName: clickhouse
      parameters:
        - key: clickhouse.profiles.web.max_bytes_to_read
          value: "200000000000"
EOF

Monitor progress:

kubectl get opsrequest ch-reconfiguring -n demo -w

Example Output

NAME               TYPE            CLUSTER              STATUS    PROGRESS   AGE
ch-reconfiguring   Reconfiguring   clickhouse-cluster   Succeed   -/-        10s

Verify the parameter was applied:

CH_POD=$(kubectl get pods -n demo -l app.kubernetes.io/instance=clickhouse-cluster \
  -o jsonpath='{.items[0].metadata.name}')

kubectl exec -n demo $CH_POD -c clickhouse -- \
  clickhouse-client --user admin --password password123 \
  --query "SELECT name, value FROM system.settings WHERE name = 'max_bytes_to_read'"

Example Output

max_bytes_to_read	200000000000

Immutable Parameters

The following parameters cannot be changed via OpsRequest (they require a cluster rebuild):

clickhouse.http_port
clickhouse.https_port
clickhouse.tcp_port
clickhouse.interserver_http_port
clickhouse.listen_host
clickhouse.macros
clickhouse.logger

Cleanup

kubectl delete opsrequest ch-reconfiguring -n demo --ignore-not-found

Update a ClickHouse Parameter

The following example updates clickhouse.profiles.web.max_bytes_to_read, which limits the maximum bytes read per query for the web profile:

kubectl apply -f - <<EOF apiVersion: operations.kubeblocks.io/v1alpha1 kind: OpsRequest metadata: name: ch-reconfiguring namespace: demo spec: clusterName: clickhouse-cluster type: Reconfiguring reconfigures: - componentName: clickhouse parameters: - key: clickhouse.profiles.web.max_bytes_to_read value: "200000000000" EOF

Monitor progress:

kubectl get opsrequest ch-reconfiguring -n demo -w

Example Output

NAME               TYPE            CLUSTER              STATUS    PROGRESS   AGE
ch-reconfiguring   Reconfiguring   clickhouse-cluster   Succeed   -/-        10s

Verify the parameter was applied:

CH_POD=$(kubectl get pods -n demo -l app.kubernetes.io/instance=clickhouse-cluster \ -o jsonpath='{.items[0].metadata.name}') kubectl exec -n demo $CH_POD -c clickhouse -- \ clickhouse-client --user admin --password password123 \ --query "SELECT name, value FROM system.settings WHERE name = 'max_bytes_to_read'"

Example Output

max_bytes_to_read	200000000000