drain old web slot before blue-green shutdown

deploy/scripts/deploy-blue-green-service.sh

@@ -64,10 +64,11 @@ ROUTING_NETWORK="${BLUE_GREEN_ROUTING_NETWORK:-firstleg-${DEPLOY_ENV}-routing}"
 HEALTH_TIMEOUT="${DEPLOY_HEALTH_TIMEOUT_SECONDS:-240}"
 HEALTH_POLL="${DEPLOY_HEALTH_POLL_SECONDS:-5}"
 STABILIZATION_SECONDS="${BLUE_GREEN_STABILIZATION_SECONDS:-10}"
+DRAIN_SECONDS="${BLUE_GREEN_DRAIN_SECONDS:-30}"
 STOP_TIMEOUT="${BLUE_GREEN_STOP_TIMEOUT_SECONDS:-45}"
 IMAGE="$IMAGE_REPOSITORY/$SERVICE:$IMAGE_TAG"
 
-for value in "$HEALTH_TIMEOUT" "$HEALTH_POLL" "$STABILIZATION_SECONDS" "$STOP_TIMEOUT"; do
+for value in "$HEALTH_TIMEOUT" "$HEALTH_POLL" "$STABILIZATION_SECONDS" "$DRAIN_SECONDS" "$STOP_TIMEOUT"; do
   case "$value" in ''|*[!0-9]*) echo "蓝绿时间参数必须为非负整数: $value" >&2; exit 2 ;; esac
 done
 
@@ -365,6 +366,10 @@ fi
 
 old_container_stopped=false
 if [ -n "$active_container" ] && docker inspect "$active_container" >/dev/null 2>&1; then
+  if [ "$DRAIN_SECONDS" -gt 0 ]; then
+    echo "蓝绿切换后连接排空 ${DRAIN_SECONDS}s，旧 Web 实例保持运行: $active_container"
+    sleep "$DRAIN_SECONDS"
+  fi
   echo "优雅停止旧 Web 实例: $active_container"
   docker stop --time "$STOP_TIMEOUT" "$active_container" >/dev/null
   old_container_stopped=true