feat(helm): add persistent volume for local model cache (#861)

* feat(helm): add persistent volume for local model cache

When using local reranker (e.g., BAAI/bge-reranker-v2-m3) or local
embedding models, the models are downloaded to /home/hindsight/.cache
on every pod restart, causing slow startup and unnecessary bandwidth.

Add optional persistent volume support:
- api: PVC mounted at /home/hindsight/.cache
- worker: volumeClaimTemplate (StatefulSet) at same path

Disabled by default. Enable via:
  api.persistence.modelCache.enabled: true
  worker.persistence.modelCache.enabled: true

Closes #860

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(helm): add extraVolumes and extraVolumeMounts for api and worker

Allow users to mount arbitrary volumes (configMaps, secrets, emptyDir,
etc.) into api and worker pods via values, following common helm chart
library conventions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

helm/hindsight/templates/api-deployment.yaml

@@ -95,6 +95,27 @@ spec:
           {{- toYaml .Values.api.readinessProbe | nindent 10 }}
         resources:
           {{- toYaml .Values.api.resources | nindent 10 }}
+        {{- if or .Values.api.persistence.modelCache.enabled .Values.api.extraVolumeMounts }}
+        volumeMounts:
+        {{- if .Values.api.persistence.modelCache.enabled }}
+        - name: model-cache
+          mountPath: /home/hindsight/.cache
+        {{- end }}
+        {{- with .Values.api.extraVolumeMounts }}
+        {{- toYaml . | nindent 8 }}
+        {{- end }}
+        {{- end }}
+      {{- if or .Values.api.persistence.modelCache.enabled .Values.api.extraVolumes }}
+      volumes:
+      {{- if .Values.api.persistence.modelCache.enabled }}
+      - name: model-cache
+        persistentVolumeClaim:
+          claimName: {{ include "hindsight.fullname" . }}-api-model-cache
+      {{- end }}
+      {{- with .Values.api.extraVolumes }}
+      {{- toYaml . | nindent 6 }}
+      {{- end }}
+      {{- end }}
       {{- with .Values.nodeSelector }}
       nodeSelector:
         {{- toYaml . | nindent 8 }}

helm/hindsight/templates/api-model-cache-pvc.yaml

@@ -0,0 +1,21 @@
+{{- if and .Values.api.enabled .Values.api.persistence.modelCache.enabled }}
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: {{ include "hindsight.fullname" . }}-api-model-cache
+  labels:
+    {{- include "hindsight.api.labels" . | nindent 4 }}
+  {{- with .Values.api.persistence.modelCache.annotations }}
+  annotations:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
+spec:
+  accessModes:
+    {{- toYaml .Values.api.persistence.modelCache.accessModes | nindent 4 }}
+  {{- if .Values.api.persistence.modelCache.storageClass }}
+  storageClassName: {{ .Values.api.persistence.modelCache.storageClass }}
+  {{- end }}
+  resources:
+    requests:
+      storage: {{ .Values.api.persistence.modelCache.size }}
+{{- end }}

helm/hindsight/templates/worker-statefulset.yaml

@@ -95,6 +95,16 @@ spec:
           {{- toYaml .Values.worker.readinessProbe | nindent 10 }}
         resources:
           {{- toYaml .Values.worker.resources | nindent 10 }}
+        {{- if or .Values.worker.persistence.modelCache.enabled .Values.worker.extraVolumeMounts }}
+        volumeMounts:
+        {{- if .Values.worker.persistence.modelCache.enabled }}
+        - name: model-cache
+          mountPath: /home/hindsight/.cache
+        {{- end }}
+        {{- with .Values.worker.extraVolumeMounts }}
+        {{- toYaml . | nindent 8 }}
+        {{- end }}
+        {{- end }}
       {{- with .Values.nodeSelector }}
       nodeSelector:
         {{- toYaml . | nindent 8 }}
@@ -107,4 +117,26 @@ spec:
       tolerations:
         {{- toYaml . | nindent 8 }}
       {{- end }}
+      {{- with .Values.worker.extraVolumes }}
+      volumes:
+      {{- toYaml . | nindent 6 }}
+      {{- end }}
+  {{- if .Values.worker.persistence.modelCache.enabled }}
+  volumeClaimTemplates:
+  - metadata:
+      name: model-cache
+      {{- with .Values.worker.persistence.modelCache.annotations }}
+      annotations:
+        {{- toYaml . | nindent 8 }}
+      {{- end }}
+    spec:
+      accessModes:
+        {{- toYaml .Values.worker.persistence.modelCache.accessModes | nindent 8 }}
+      {{- if .Values.worker.persistence.modelCache.storageClass }}
+      storageClassName: {{ .Values.worker.persistence.modelCache.storageClass }}
+      {{- end }}
+      resources:
+        requests:
+          storage: {{ .Values.worker.persistence.modelCache.size }}
+  {{- end }}
 {{- end }}

helm/hindsight/values.yaml

@@ -67,6 +67,33 @@ api:
   # Pod affinity/anti-affinity (overrides global affinity for this component)
   # affinity: {}
 
+  # Persistent volume for local model cache (reranker, embeddings)
+  # Models are downloaded to /home/hindsight/.cache on first use.
+  # Without persistence, models are re-downloaded on every pod restart.
+  persistence:
+    modelCache:
+      enabled: false
+      size: 5Gi
+      storageClass: ""
+      accessModes:
+        - ReadWriteOnce
+      annotations: {}
+
+  # Extra volume mounts for the api container
+  # e.g.
+  # extraVolumeMounts:
+  #   - name: my-volume
+  #     mountPath: /mnt/my-volume
+  extraVolumeMounts: []
+
+  # Extra volumes for the api pod
+  # e.g.
+  # extraVolumes:
+  #   - name: my-volume
+  #     configMap:
+  #       name: my-configmap
+  extraVolumes: []
+
   # Environment variables
   env:
     #HINDSIGHT_API_LLM_PROVIDER: "groq"
@@ -140,6 +167,32 @@ worker:
   # Pod affinity/anti-affinity (overrides global affinity for this component)
   # affinity: {}
 
+  # Persistent volume for local model cache (reranker, embeddings)
+  # Uses volumeClaimTemplates since worker is a StatefulSet.
+  persistence:
+    modelCache:
+      enabled: false
+      size: 5Gi
+      storageClass: ""
+      accessModes:
+        - ReadWriteOnce
+      annotations: {}
+
+  # Extra volume mounts for the worker container
+  # e.g.
+  # extraVolumeMounts:
+  #   - name: my-volume
+  #     mountPath: /mnt/my-volume
+  extraVolumeMounts: []
+
+  # Extra volumes for the worker pod
+  # e.g.
+  # extraVolumes:
+  #   - name: my-volume
+  #     configMap:
+  #       name: my-configmap
+  extraVolumes: []
+
   # Secret environment variables (inherited from api.secrets if not specified)
   secrets: {}