Prefactoring before adding metrics support.

- change deploy tool to use the flag package where appropriate rather
  than positional arguments for everything, as they would become a mess
  when another is added,
- rename daemonSetTemplate to deploymentTemplate as it already contains
  more than the daemonset, and will continue to grow soon,
- rename some variables to mention CRI to make room for an upcoming
  non-cri client/connection,
- extract a logging package, to be used in upcoming subcommand,
- in README and GHA workflow, correct deploy tool usage
- in README, mention daemonset in individual commands,

.github/workflows/build.yaml

@@ -45,10 +45,10 @@ jobs:
       - name: Prepare manifests for linting
         run: |
           mkdir manifests
-          go run deploy/main.go my-images v0.0.8 vanilla > manifests/vanilla.yaml
-          go run deploy/main.go my-images v0.0.8 ocp > manifests/ocp.yaml
-          go run deploy/main.go my-images v0.0.8 vanilla my-secret > manifests/vanilla-with-secret.yaml
-          go run deploy/main.go my-images v0.0.8 ocp my-secret > manifests/ocp-with-secret.yaml
+          go run deploy/*.go --k8s-flavor vanilla my-images > manifests/vanilla.yaml
+          go run deploy/*.go --k8s-flavor ocp my-images > manifests/ocp.yaml
+          go run deploy/*.go --k8s-flavor vanilla --secret my-secret my-images > manifests/vanilla-with-secret.yaml
+          go run deploy/*.go --k8s-flavor ocp --secret my-secret my-images > manifests/ocp-with-secret.yaml
 
       - name: kube-linter
         uses: stackrox/[email protected]

README.md

@@ -11,12 +11,12 @@ Talks directly to Container Runtime Interface ([CRI](https://kubernetes.io/docs/
 ### `image-prefetcher`
 
 - main binary,
-- meant to be run in pods of a DaemonSet,
 - shipped as an OCI image,
 - provides two subcommands:
-  - `fetch`: runs the actual image pulls via CRI, meant to run as an init container,
+  - `fetch`: runs the actual image pulls via CRI, meant to run as an init container
+    of DaemonSet pods.
     Requires access to the CRI UNIX domain socket from the host.
-  - `sleep`: just sleeps forever, meant to run as the main container,
+  - `sleep`: just sleeps forever, meant to run as the main container of DaemonSet pods.
 
 ### `deploy`
 
@@ -29,21 +29,22 @@ Talks directly to Container Runtime Interface ([CRI](https://kubernetes.io/docs/
 
    You can run many instances independently.
 
-   It requires a few arguments:
-   - **name** of the instance.
-     This also determines the name of a `ConfigMap` supplying names of images to fetch.
-   - `image-prefetcher` OCI image **version**. See [list of existing tags](https://quay.io/repository/mowsiany/image-prefetcher?tab=tags).
-   - **cluster flavor**. Currently one of:
+   It requires a single positional argument for the **name** of the instance.
+   This also determines the name of a `ConfigMap` supplying names of images to fetch.
+
+   It also accepts a few optional flags:
+   - `--version`: `image-prefetcher` OCI image tag. See [list of existing tags](https://quay.io/repository/mowsiany/image-prefetcher?tab=tags).
+   - `--k8s-flavor` depending on the cluster. Currently one of:
      - `vanilla`: a generic Kubernetes distribution without additional restrictions.
      - `ocp`: OpenShift, which requires explicitly granting special privileges.
-   - optional **image pull `Secret` name**. Required if the images are not pullable anonymously.
+   - `--secret`: image pull `Secret` name. Required if the images are not pullable anonymously.
      This image pull secret should be usable for all images fetched by the given instance.
      If provided, it must be of type `kubernetes.io/dockerconfigjson` and exist in the same namespace.
 
    Example:
 
    ```
-   go run github.com/stackrox/image-prefetcher/deploy@main my-images v0.0.8 vanilla > manifest.yaml
+   go run github.com/stackrox/image-prefetcher/deploy@master my-images v0.0.8 vanilla > manifest.yaml
    ```
 
 2. Prepare an image list. This should be a plain text file with one image name per line.

cmd/fetch.go

@@ -1,12 +1,12 @@
 package cmd
 
 import (
-	"log/slog"
 	"os"
 	"strings"
 	"time"
 
 	"github.com/stackrox/image-prefetcher/internal"
+	"github.com/stackrox/image-prefetcher/internal/logging"
 
 	"github.com/spf13/cobra"
 )
@@ -19,11 +19,7 @@ var fetchCmd = &cobra.Command{
 
 It talks to Container Runtime Interface API to pull images in parallel, with retries.`,
 	RunE: func(cmd *cobra.Command, args []string) error {
-		opts := &slog.HandlerOptions{AddSource: true}
-		if debug {
-			opts.Level = slog.LevelDebug
-		}
-		logger := slog.New(slog.NewTextHandler(os.Stderr, opts))
+		logger := logging.GetLogger()
 		timing := internal.TimingConfig{
 			ImageListTimeout:          imageListTimeout,
 			InitialPullAttemptTimeout: initialPullAttemptTimeout,
@@ -45,7 +41,6 @@ var (
 	criSocket                 string
 	dockerConfigJSONPath      string
 	imageListFile             string
-	debug                     bool
 	imageListTimeout          = time.Minute
 	initialPullAttemptTimeout = 30 * time.Second
 	maxPullAttemptTimeout     = 5 * time.Minute
@@ -56,11 +51,11 @@ var (
 
 func init() {
 	rootCmd.AddCommand(fetchCmd)
+	logging.AddFlags(fetchCmd.Flags())
 
 	fetchCmd.Flags().StringVar(&criSocket, "cri-socket", "/run/containerd/containerd.sock", "Path to CRI UNIX socket.")
 	fetchCmd.Flags().StringVar(&dockerConfigJSONPath, "docker-config", "", "Path to docker config json file.")
 	fetchCmd.Flags().StringVar(&imageListFile, "image-list-file", "", "Path to text file containing images to pull (one per line).")
-	fetchCmd.Flags().BoolVar(&debug, "debug", false, "Whether to enable debug logging.")
 
 	fetchCmd.Flags().DurationVar(&imageListTimeout, "image-list-timeout", imageListTimeout, "Timeout for image list calls (for debugging).")
 	fetchCmd.Flags().DurationVar(&initialPullAttemptTimeout, "initial-pull-attempt-timeout", initialPullAttemptTimeout, "Timeout for initial image pull call. Each subsequent attempt doubles it until max.")

deploy/flavor.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"slices"
+)
+
+type k8sFlavorType string
+
+func (k *k8sFlavorType) UnmarshalText(text []byte) error {
+	if slices.Contains(allFlavors, string(text)) {
+		*k = k8sFlavorType(text)
+		return nil
+	}
+	return fmt.Errorf("unknown k8s flavor %q", text)
+}
+
+func (k *k8sFlavorType) MarshalText() (text []byte, err error) {
+	return []byte(*k), nil
+}
+
+func flavor(flavor string) *k8sFlavorType {
+	var f k8sFlavorType
+	if err := f.UnmarshalText([]byte(flavor)); err != nil {
+		log.Fatal(err)
+	}
+	return &f
+}

deploy/main.go

@@ -2,8 +2,11 @@ package main
 
 import (
 	_ "embed"
+	"flag"
+	"fmt"
 	"log"
 	"os"
+	"strings"
 	"text/template"
 )
 
@@ -16,23 +19,38 @@ type settings struct {
 	NeedsPrivileged bool
 }
 
+const (
+	vanillaFlavor = "vanilla"
+	ocpFlavor     = "ocp"
+)
+
+var allFlavors = []string{vanillaFlavor, ocpFlavor}
+
 const imageRepo = "quay.io/stackrox-io/image-prefetcher"
 
 //go:embed deployment.yaml.gotpl
-var daemonSetTemplate string
+var deploymentTemplate string
+
+var (
+	version   string
+	k8sFlavor k8sFlavorType
+	secret    string
+)
+
+func init() {
+	flag.StringVar(&version, "version", "v0.1.0", "Version of image prefetcher OCI image.")
+	flag.TextVar(&k8sFlavor, "k8s-flavor", flavor(vanillaFlavor), fmt.Sprintf("Kubernetes flavor. Accepted values: %s", strings.Join(allFlavors, ",")))
+	flag.StringVar(&secret, "secret", "", "Kubernetes image pull Secret to use when pulling.")
+}
 
 func main() {
-	if len(os.Args) < 4 {
-		println("Usage:", os.Args[0], "<name> <version> vanilla|ocp [secret]")
+	flag.Parse()
+	if len(flag.Args()) < 1 {
+		println("Usage:", os.Args[0], "[ FLAGS ] <name>")
 		os.Exit(1)
 	}
-	name := os.Args[1]
-	version := os.Args[2]
-	isOcp := os.Args[3] == "ocp"
-	secret := ""
-	if len(os.Args) > 4 {
-		secret = os.Args[4]
-	}
+	name := flag.Arg(0)
+	isOcp := k8sFlavor == ocpFlavor
 
 	s := settings{
 		Name:            name,
@@ -42,7 +60,7 @@ func main() {
 		IsCRIO:          isOcp,
 		NeedsPrivileged: isOcp,
 	}
-	tmpl := template.Must(template.New("deployment").Parse(daemonSetTemplate))
+	tmpl := template.Must(template.New("deployment").Parse(deploymentTemplate))
 	if err := tmpl.Execute(os.Stdout, s); err != nil {
 		log.Fatal(err)
 	}

internal/logging/main.go

@@ -0,0 +1,22 @@
+package logging
+
+import (
+	"log/slog"
+	"os"
+
+	"github.com/spf13/pflag"
+)
+
+var debug bool
+
+func GetLogger() *slog.Logger {
+	opts := &slog.HandlerOptions{AddSource: true}
+	if debug {
+		opts.Level = slog.LevelDebug
+	}
+	return slog.New(slog.NewTextHandler(os.Stderr, opts))
+}
+
+func AddFlags(flags *pflag.FlagSet) {
+	flags.BoolVar(&debug, "debug", false, "Whether to enable debug logging.")
+}

internal/main.go

@@ -28,13 +28,13 @@ func Run(logger *slog.Logger, criSocketPath string, dockerConfigJSONPath string,
 	ctx, cancel := context.WithTimeout(context.Background(), timing.OverallTimeout)
 	defer cancel()
 
-	clientConn, err := grpc.DialContext(ctx, "unix://"+criSocketPath, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	criConn, err := grpc.DialContext(ctx, "unix://"+criSocketPath, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	if err != nil {
 		return fmt.Errorf("failed to dial CRI socket %q: %w", criSocketPath, err)
 	}
-	client := criV1.NewImageServiceClient(clientConn)
+	criClient := criV1.NewImageServiceClient(criConn)
 
-	if err := listImagesForDebugging(ctx, logger, client, timing.ImageListTimeout, "before"); err != nil {
+	if err := listImagesForDebugging(ctx, logger, criClient, timing.ImageListTimeout, "before"); err != nil {
 		return fmt.Errorf("failed to list images for debugging before pulling: %w", err)
 	}
 
@@ -54,12 +54,12 @@ func Run(logger *slog.Logger, criSocketPath string, dockerConfigJSONPath string,
 				},
 				Auth: auth,
 			}
-			go pullImageWithRetries(ctx, logger.With("image", imageName, "authNum", i), &wg, client, request, timing)
+			go pullImageWithRetries(ctx, logger.With("image", imageName, "authNum", i), &wg, criClient, request, timing)
 		}
 	}
 	wg.Wait()
 	logger.Info("pulling images finished")
-	if err := listImagesForDebugging(ctx, logger, client, timing.ImageListTimeout, "after"); err != nil {
+	if err := listImagesForDebugging(ctx, logger, criClient, timing.ImageListTimeout, "after"); err != nil {
 		return fmt.Errorf("failed to list images for debugging after pulling: %w", err)
 	}
 	return nil