Update enableDeltaXDS configuration in values.yaml to true and add ISTIO_DELTA_XDS environment variable in pod template

Change-Id: I3df3446264894c710da6026f78d3440d6c6392e1
Co-developed-by: Cursor <noreply@cursor.com>

helm/core/templates/_pod.tpl

@@ -123,6 +123,8 @@ template:
         - name: LITE_METRICS
           value: "on"
         {{- end }}
+        - name: ISTIO_DELTA_XDS
+          value: "{{ .Values.global.enableDeltaXDS }}"
         {{- if include "skywalking.enabled" . }}
         - name: ISTIO_BOOTSTRAP_OVERRIDE
           value: /etc/istio/custom-bootstrap/custom_bootstrap.json

helm/core/values.yaml

@@ -9,8 +9,8 @@ global:
   xdsMaxRecvMsgSize: "104857600"
   defaultUpstreamConcurrencyThreshold: 10000
   enableSRDS: true
-  # -- Whether to enable Istio delta xDS. Default is false due to SRDS compatibility.
-  enableDeltaXDS: false
+  # -- Whether to enable Istio delta xDS, default is false.
+  enableDeltaXDS: true
   # -- Whether to enable Redis(redis-stack-server) for Higress, default is false.
   enableRedis: false
   enablePluginServer: false