Merge pull request #122 from rajathagasthya/apply-crds

Refactor crdutil library and add delete support

Author: rajathagasthya

cmd/apply-crds/main.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2025 NVIDIA CORPORATION & AFFILIATES
+
+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.
+*/
+
+// Package main demonstrates how to use the crdutil package to manage CRDs.
+// This is a simple example that shows how to apply and delete CRDs from directories or files.
+package main
+
+import (
+	"context"
+	"flag"
+	"log"
+
+	"github.com/NVIDIA/k8s-operator-libs/pkg/crdutil"
+)
+
+var (
+	crdsPath  string
+	operation string
+)
+
+func init() {
+	flag.StringVar(&crdsPath, "crds-path", "",
+		"Path to CRD manifest file or directory (directories are searched recursively)")
+	flag.StringVar(&operation, "operation", "apply", "Operation to perform: 'apply' or 'delete'")
+}
+
+func main() {
+	flag.Parse()
+
+	if crdsPath == "" {
+		log.Fatal("Error: --crds-path flag is required")
+	}
+
+	ctx := context.Background()
+
+	switch operation {
+	case "apply":
+		if err := crdutil.ProcessCRDs(ctx, []string{crdsPath}, crdutil.CRDOperationApply); err != nil {
+			log.Fatalf("Failed to apply CRDs: %v", err)
+		}
+	case "delete":
+		if err := crdutil.ProcessCRDs(ctx, []string{crdsPath}, crdutil.CRDOperationDelete); err != nil {
+			log.Fatalf("Failed to delete CRDs: %v", err)
+		}
+	default:
+		log.Fatalf("Invalid operation: %s (must be 'apply' or 'delete')", operation)
+	}
+}

examples/apply-crds/main.go

@@ -1,34 +1,41 @@
-# CRD Apply Tool
+# CRD Management Library
 
-This tool is designed to help deploy and manage Custom Resource Definitions (CRDs) in a Kubernetes cluster.
-It applies all CRDs found in specified directories, providing a solution to some of the limitations of Helm when it comes to managing CRDs.
+A Go library for deploying and managing Custom Resource Definitions (CRDs) in Kubernetes clusters.
+It supports both applying (creating/updating) and deleting CRDs from individual files or directories (searched recursively).
+
+This package is intended to be used programmatically in Go applications. An example CLI implementation is provided in [`examples/apply-crds/`](../../examples/apply-crds/) to demonstrate usage.
 
 ## Motivation
 
 While Helm is commonly used for managing Kubernetes resources, it has certain restrictions with CRDs:
 
-- CRDs placed in Helm's top-level `crds/` directory are not updated on upgrades or rollbacks.
-- Placing CRDs in Helm’s `templates/` directory is not entirely safe, as deletions and upgrades of CRDs are not always handled properly.
+- CRDs placed in a Helm chart's top-level `crds/` directory are installed once but not updated on upgrades or deleted on uninstalls.
+- Placing CRDs in a Helm chart's `templates/` directory allows updates but can be risky since CRDs are deleted on uninstall unless protected with the `helm.sh/resource-policy: keep` annotation.
 
-This tool offers a more reliable way to apply CRDs, ensuring they are created or updated as needed.
+This library offers a more reliable way to manage CRDs, ensuring they are created, updated, or deleted as needed.
 
 ## Features
 
-- **Apply CRDs from multiple directories**: Allows specifying multiple directories containing CRD YAML manifests.
-- **Recursive directory search**: Walks through each specified directory to find and apply all YAML files.
-- **Safe update mechanism**: Checks if a CRD already exists; if so, it updates it with the latest version.
+- **Apply and Delete CRDs**: Supports both applying (creating/updating) and deleting CRDs.
+- **Flexible input**: Accepts individual YAML files or directories (or a mix of both).
+- **Recursive directory search**: Automatically walks through directories to find and process all YAML files.
+- **Safe update mechanism**: Checks if a CRD already exists; if so, it updates it with retry-on-conflict logic.
+- **Idempotent operations**: Both apply and delete operations can be run multiple times safely.
 - **Handles multiple YAML documents**: Supports files containing multiple CRD documents separated by YAML document delimiters.
 
-## Usage
+## Quick Start
 
-Compile and run the tool by providing the `-crds-dir` flag with paths to the directories containing the CRD YAML files:
+For usage examples, see [`examples/apply-crds/`](../../examples/apply-crds/).
 
-```bash
-go build -o crd-apply-tool
-./crd-apply-tool -crds-dir /path/to/crds1 -crds-dir /path/to/crds2
-```
+## Integration Examples
+
+### Using in Helm Hooks
 
-In a Helm pre-install hook it can look like:
+You can build a custom binary using this library and deploy it as a Helm hook. Here's an example:
+
+#### Pre-install/Pre-upgrade Hook
+
+Apply CRDs before installation or upgrade:
 
 ```yaml
 apiVersion: batch/v1
@@ -51,11 +58,10 @@ spec:
           command:
             - /apply-crds
           args:
-              - --crds-dir=/crds/operator
+            - --crds-path=/opt/config/crds
+            - --operation=apply
 ```
 
-> Note: the image must contain all your CRDs in e.g. the `/crds/operator` directory.
-
-## Flags
+#### Pre-delete Hook
 
-- `-crds-dir` (required): Specifies a directory path that contains the CRD manifests in YAML format. This flag can be provided multiple times to apply CRDs from multiple directories.
+By default, Helm does not delete CRDs when a chart is uninstalled. Use caution when deleting CRDs in a pre-delete Helm hook. Deleting a CRD also removes all associated Custom Resources (CRs), which can lead to data loss if users upgrade by uninstalling and reinstalling the chart.