BAC-492 - Prevent Rollout From Losing spec.replicas During ArgoCD Syn…

src/commands/argo-deploy-application.yml

@@ -215,6 +215,14 @@ steps:
         - argo-app-previous-status:
             release-name: << parameters.release-name >>
 
+  - run:
+      name: Prepare HPA transition
+      environment:
+        ARGO_PARAMETERS_FILE: /tmp/argo-parameters/parameters.yaml
+        RELEASE_NAME: << parameters.release-name >>
+        NAMESPACE: << parameters.namespace >>
+      command: << include(scripts/argo_hpa_transition.sh) >>
+
   - run:
       name: Upsert Argo Application
       command: |

src/scripts/argo_hpa_transition.sh

@@ -0,0 +1,99 @@
+#!/bin/bash
+
+# This script prepares a Rollout resource for HPA transition by cleaning the
+# spec.replicas field from the kubectl last-applied-configuration annotation.
+#
+# When transitioning from fixed replicas to HPA-managed replicas, kubectl's
+# three-way merge interprets the removal of spec.replicas from the desired
+# manifest as an intentional deletion, causing Kubernetes to default to 1 replica.
+# By removing the field from last-applied-configuration beforehand, the three-way
+# merge sees "was absent, still absent" and preserves the live replica count.
+#
+# Environment variables:
+#   ARGO_PARAMETERS_FILE  - Path to the rendered Helm parameters file
+#   RELEASE_NAME          - Name of the Rollout resource
+#   NAMESPACE             - Kubernetes namespace
+
+# Colors for output
+RED="\033[0;31m"
+GREEN="\033[0;32m"
+YELLOW="\033[1;33m"
+NC="\033[0m" # No Color
+
+function usage() {
+  echo -e "${GREEN}Usage:${NC} Set the following environment variables before running this script:"
+  echo "  ARGO_PARAMETERS_FILE  Path to the rendered Helm parameters file (required)"
+  echo "  RELEASE_NAME          Name of the Rollout resource (required)"
+  echo "  NAMESPACE             Kubernetes namespace (required)"
+}
+
+function main() {
+  local parameters_file="${ARGO_PARAMETERS_FILE}"
+  local release_name="${RELEASE_NAME}"
+  local namespace="${NAMESPACE}"
+
+  # Validate required variables
+  local missing_vars=()
+  [[ -z "$parameters_file" ]] && missing_vars+=("ARGO_PARAMETERS_FILE")
+  [[ -z "$release_name" ]] && missing_vars+=("RELEASE_NAME")
+  [[ -z "$namespace" ]] && missing_vars+=("NAMESPACE")
+
+  if [[ ${#missing_vars[@]} -gt 0 ]]; then
+    echo -e "${RED}Error: The following required environment variables are missing:${NC}"
+    printf '  - %s\n' "${missing_vars[@]}"
+    usage
+    exit 2
+  fi
+
+  # Check if autoscaling is being enabled in this deploy
+  local hpa_enabled
+  hpa_enabled=$(grep -A1 'name: autoscaling\.enabled' "$parameters_file" | grep 'value:' | awk '{print $2}' || echo "false")
+
+  if [[ "$hpa_enabled" != "true" ]]; then
+    echo -e "${GREEN}HPA not enabled in this deploy, skipping.${NC}"
+    return 0
+  fi
+
+  echo -e "${YELLOW}HPA enabled — checking if spec.replicas cleanup is needed for Rollout '$release_name' in namespace '$namespace'.${NC}"
+
+  # Check if the Rollout exists (might not on first deploy)
+  if ! kubectl get rollout "$release_name" -n "$namespace" > /dev/null 2>&1; then
+    echo -e "${GREEN}Rollout '$release_name' not found (likely first deploy), skipping.${NC}"
+    return 0
+  fi
+
+  # Get the last-applied-configuration annotation
+  local last_applied
+  last_applied=$(kubectl get rollout "$release_name" -n "$namespace" \
+    -o jsonpath='{.metadata.annotations.kubectl\.kubernetes\.io/last-applied-configuration}' 2>/dev/null || echo "")
+
+  if [[ -z "$last_applied" ]]; then
+    echo -e "${GREEN}No last-applied-configuration annotation found, skipping.${NC}"
+    return 0
+  fi
+
+  # Check if spec.replicas exists in last-applied-configuration
+  if ! echo "$last_applied" | jq -e '.spec.replicas' > /dev/null 2>&1; then
+    echo -e "${GREEN}spec.replicas not present in last-applied-configuration, no cleanup needed.${NC}"
+    return 0
+  fi
+
+  local current_replicas
+  current_replicas=$(echo "$last_applied" | jq '.spec.replicas')
+  echo -e "${YELLOW}Removing spec.replicas ($current_replicas) from last-applied-configuration${NC}"
+  echo "to prevent three-way merge conflict during HPA transition."
+
+  # Remove spec.replicas from last-applied-configuration
+  local cleaned
+  cleaned=$(echo "$last_applied" | jq -c 'del(.spec.replicas)')
+
+  if ! kubectl annotate rollout "$release_name" -n "$namespace" \
+    "kubectl.kubernetes.io/last-applied-configuration=$cleaned" --overwrite; then
+    echo -e "${RED}Failed to update last-applied-configuration annotation.${NC}"
+    return 1
+  fi
+
+  echo -e "${GREEN}Successfully cleaned spec.replicas from last-applied-configuration.${NC}"
+}
+
+main "$@"