WIP [scalardb-cluster] Make Envoy optional #302
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kota2and3kan
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scalardb cluster
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Summary of Changes
Hello @kota2and3kan, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request introduces the capability to deploy ScalarDB Cluster without requiring Envoy as a mandatory component. It achieves this by making the underlying Kubernetes service configurations conditional based on an envoy.enabled flag, allowing the cluster to be exposed via a standard service instead of a headless service when Envoy is not in use. This change provides greater flexibility for users who do not need Envoy's features in their ScalarDB Cluster deployments.
Highlights
- Conditional Service Deployment: The Kubernetes Service definition for ScalarDB Cluster is now conditional. If
.Values.envoy.enabledis true, a headless service (clusterIP: None) is deployed. Otherwise, a standard Kubernetes Service (ClusterIP type, or whatever is specified by.Values.scalardbCluster.service.type) is deployed. - Dynamic Endpoint Configuration: The
SCALAR_DB_CLUSTER_MEMBERSHIP_KUBERNETES_ENDPOINT_NAMEenvironment variable within the deployment is now dynamically set. It will point to the headless service name when Envoy is enabled, and to the standard service name when Envoy is disabled, ensuring correct cluster membership discovery.
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Code Review
This pull request makes Envoy optional in the scalardb-cluster Helm chart. The service created for a non-Envoy setup is not headless, which is a requirement for Kubernetes-based cluster membership discovery. The deployment.yaml is configured to use this service for cluster membership discovery. ScalarDB's Kubernetes discovery mechanism requires a headless service to get the individual pod IPs. A regular service with a cluster IP will not work for discovery, causing the cluster formation to fail.
| {{- else }} | ||
| --- | ||
| apiVersion: v1 | ||
| kind: Service | ||
| metadata: | ||
| name: {{ include "scalardb-cluster.fullname" . }} | ||
| namespace: {{ .Release.Namespace }} | ||
| labels: | ||
| {{- include "scalardb-cluster.labels" . | nindent 4 }} | ||
| annotations: | ||
| {{- toYaml .Values.scalardbCluster.service.annotations | nindent 4 }} | ||
| spec: | ||
| type: {{ .Values.scalardbCluster.service.type }} | ||
| ports: | ||
| {{- range $key, $value := .Values.scalardbCluster.service.ports }} | ||
| - name: {{ $key }} | ||
| {{- toYaml $value | nindent 6 }} | ||
| {{- end }} | ||
| selector: | ||
| {{- include "scalardb-cluster.selectorLabels" . | nindent 4 }} | ||
| {{- end }} |
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When envoy.enabled is false, the service created in the {{- else }} block is not headless (it lacks spec.clusterIP: None). The deployment.yaml is configured to use this service for cluster membership discovery. ScalarDB's Kubernetes discovery mechanism requires a headless service to get the individual pod IPs. A regular service with a cluster IP will not work for discovery, causing the cluster formation to fail.
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ScalarDB Cluster's pod discovery feature utilizes the Endpoint resource behind the Service directly. It doesn't depend on the Headless Service. Therefore, it works if we create a Service resource even if whether it's Headless or not.
| {{- if .Values.envoy.enabled }} | ||
| - name: SCALAR_DB_CLUSTER_MEMBERSHIP_KUBERNETES_ENDPOINT_NAME | ||
| value: {{ include "scalardb-cluster.fullname" . }}-headless | ||
| {{- else }} | ||
| - name: SCALAR_DB_CLUSTER_MEMBERSHIP_KUBERNETES_ENDPOINT_NAME | ||
| value: {{ include "scalardb-cluster.fullname" . }} | ||
| {{- end }} |
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Consider refactoring this block to be more concise and avoid repeating the name field, which improves maintainability.
- name: SCALAR_DB_CLUSTER_MEMBERSHIP_KUBERNETES_ENDPOINT_NAME
value: {{ include "scalardb-cluster.fullname" . }}{{ if .Values.envoy.enabled }}-headless{{ end }}
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