feat: add cluster-name validator, update README (#199)

catalog/gitops/configsync/Kptfile

@@ -16,7 +16,13 @@ info:
     2.  Manage plain KRM or manually rendered blueprints
     3.  Automatically apply your config changes to your Config Controller
         cluster on merge
+
+    NOTE: cluster-name must not exceed 25 characters in length, as it is
+    included in the service account ID which has a maximum character length.
 pipeline:
   mutators:
     - image: gcr.io/kpt-fn/apply-setters:v0.1
       configPath: setters.yaml
+  validators:
+    - image: gcr.io/kpt-fn/starlark:v0.4
+      configPath: validation.yaml

catalog/gitops/configsync/README.md

@@ -14,6 +14,9 @@ After installing this blueprint, you will be able to:
 3.  Automatically apply your config changes to your Config Controller
     cluster on merge
 
+NOTE: cluster-name must not exceed 25 characters in length, as it is
+included in the service account ID which has a maximum character length.
+
 ## Setters
 
 |      Name       |      Value      | Type | Count |

catalog/gitops/configsync/setters.yaml

@@ -19,6 +19,7 @@ metadata:
     config.kubernetes.io/local-config: "true"
 data:
   namespace: config-control
+  # cluster-name must not exceed 25 characters in length
   cluster-name: cluster-name
   configsync-dir: config
   deployment-repo: deployment-repo

catalog/gitops/configsync/validation.yaml

@@ -0,0 +1,25 @@
+# Copyright 2022 Google LLC
+#
+# 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.
+apiVersion: fn.kpt.dev/v1alpha1
+kind: StarlarkRun
+metadata:
+  name: validate-cluster-name-length
+  annotations:
+    config.kubernetes.io/local-config: 'true'
+source: |
+  for resource in ctx.resource_list["items"]:
+    if resource["kind"] == "IAMServiceAccount" and \
+    len(resource["metadata"]["name"]) > 30:
+      fail("cluster-name cannot exceed 25 characters in length:", \
+      len(resource["metadata"]["name"])-5)