Examples: only terminate vtadmin if it was started

examples/common/scripts/vtadmin-down.sh

@@ -1,9 +1,40 @@
 #!/bin/bash
 
+# Copyright 2023 The Vitess Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 source "$(dirname "${BASH_SOURCE[0]:-$0}")/../env.sh"
 
-echo "Stopping vtadmin-web..."
-kill -9 "$(cat "$VTDATAROOT/tmp/vtadmin-web.pid")"
+function stop_vtadmin() {
+  local name="$1"
+  local file="$2"
+
+  if [[ -z ${1} || -z ${2} ]]; then
+    fail "A binary name and PID file must be specified when attempting to shutdown vtadmin"
+  fi
+  if [[ -e "$file" ]]; then
+    echo "Stopping $name..."
+    local pid=$(cat "$file")
+    kill $pid
+    # Wait for the process to terminate
+    while ps -p $pid > /dev/null; do
+      sleep 1
+    done
+  else
+    echo "Skipping stopping $name because no pid file."
+  fi
+}
 
-echo "Stopping vtadmin-api..."
-kill -9 "$(cat "$VTDATAROOT/tmp/vtadmin-api.pid")"
+stop_vtadmin "vtadmin-web" "$VTDATAROOT/tmp/vtadmin-web.pid"
+stop_vtadmin "vtadmin-api" "$VTDATAROOT/tmp/vtadmin-api.pid"