fix: pin scheduler-k3s:preview deployment id to the deployed release

Without this, the preview build invented a fresh timestamp for
`Values.global.deployment_id` and the resulting diff showed every
Deployment changing its `app.kubernetes.io/version` annotation - even when
nothing semantically changed. CommandPreview now reads the deployment id
out of `release.Chart.Metadata.Version` and passes it through a new
`BuildOptions.OverrideDeploymentID` parameter so the previewed manifests
carry the same version label as the live release. The deploy path still
generates a fresh timestamp.

plugins/scheduler-k3s/chart.go

@@ -33,6 +33,15 @@ type BuildResult struct {
 	KustomizeRootPath string
 }
 
+// BuildOptions configures non-default behavior for BuildAppChart.
+type BuildOptions struct {
+	// OverrideDeploymentID, when non-zero, replaces the timestamp-derived
+	// deployment id. CommandPreview uses this to reuse the currently-deployed
+	// release's id so app.kubernetes.io/version annotation churn does not
+	// appear in the diff.
+	OverrideDeploymentID int64
+}
+
 // BuildAppChart constructs a Helm chart on disk that reflects dokku's configured
 // state for the given app and image tag. It reads from the Kubernetes cluster
 // where required (for KEDA values and existing cron-job suffixes) but performs
@@ -42,7 +51,7 @@ type BuildResult struct {
 // The returned BuildResult holds the absolute chart path and the parameters a
 // subsequent Helm Install/Upgrade (dry-run or real) needs. The caller must
 // os.RemoveAll(result.ChartDir) when finished.
-func BuildAppChart(ctx context.Context, appName, imageTag string) (BuildResult, error) {
+func BuildAppChart(ctx context.Context, appName, imageTag string, opts BuildOptions) (BuildResult, error) {
 	var result BuildResult
 
 	processesRes, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
@@ -142,7 +151,10 @@ func BuildAppChart(ctx context.Context, appName, imageTag string) (BuildResult,
 		return cleanup(fmt.Errorf("Error creating chart templates directory: %w", err))
 	}
 
-	deploymentId := time.Now().Unix()
+	deploymentId := opts.OverrideDeploymentID
+	if deploymentId == 0 {
+		deploymentId = time.Now().Unix()
+	}
 	imagePullSecrets := getComputedImagePullSecrets(appName)
 	if imagePullSecrets == "" {
 		dockerConfigPath := filepath.Join(registry.GetComputedAppRegistryConfigDir(appName), "config.json")

plugins/scheduler-k3s/preview.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
+	"strconv"
+	"strings"
 	"syscall"
 
 	"github.com/dokku/dokku/plugins/common"
@@ -14,6 +16,7 @@ import (
 	"helm.sh/helm/v3/pkg/chart"
 	"helm.sh/helm/v3/pkg/chart/loader"
 	"helm.sh/helm/v3/pkg/cli"
+	"helm.sh/helm/v3/pkg/release"
 	"helm.sh/helm/v3/pkg/storage/driver"
 )
 
@@ -50,29 +53,36 @@ func CommandPreview(appName string, diffContext int, showSecrets bool, showSecre
 		cancel()
 	}()
 
-	chartResult, err := BuildAppChart(ctx, appName, "")
+	namespace := getComputedNamespace(appName)
+	helmAgent, err := NewHelmAgent(namespace, DevNullPrinter)
+	if err != nil {
+		return fmt.Errorf("Error creating helm agent: %w", err)
+	}
+
+	currentRelease, err := fetchCurrentRelease(helmAgent, appName)
+	if err != nil {
+		return err
+	}
+
+	buildOpts := BuildOptions{}
+	if currentRelease != nil {
+		buildOpts.OverrideDeploymentID = deploymentIDFromRelease(currentRelease)
+	}
+
+	chartResult, err := BuildAppChart(ctx, appName, "", buildOpts)
 	if err != nil {
 		return err
 	}
 	defer os.RemoveAll(chartResult.ChartDir)
 
-	helmAgent, err := NewHelmAgent(chartResult.Namespace, DevNullPrinter)
-	if err != nil {
-		return fmt.Errorf("Error creating helm agent: %w", err)
-	}
-
 	chartRequested, err := loadChartForPreview(chartResult.ChartPath)
 	if err != nil {
 		return err
 	}
 
-	currentManifest, releaseExists, err := fetchCurrentManifest(helmAgent, chartResult.ReleaseName)
-	if err != nil {
-		return err
-	}
-
-	var proposedManifest string
-	if releaseExists {
+	var currentManifest, proposedManifest string
+	if currentRelease != nil {
+		currentManifest = currentRelease.Manifest
 		proposedManifest, err = renderUpgradeDryRun(ctx, helmAgent, chartResult, chartRequested)
 	} else {
 		proposedManifest, err = renderInstallDryRun(ctx, helmAgent, chartResult, chartRequested)
@@ -108,16 +118,38 @@ func loadChartForPreview(chartPath string) (*chart.Chart, error) {
 	return chartRequested, nil
 }
 
-func fetchCurrentManifest(helmAgent *HelmAgent, releaseName string) (string, bool, error) {
+func fetchCurrentRelease(helmAgent *HelmAgent, releaseName string) (*release.Release, error) {
 	getAction := action.NewGet(helmAgent.Configuration)
 	rel, err := getAction.Run(releaseName)
 	if err != nil {
 		if errors.Is(err, driver.ErrReleaseNotFound) {
-			return "", false, nil
+			return nil, nil
 		}
-		return "", false, fmt.Errorf("Error fetching current release: %w", err)
+		return nil, fmt.Errorf("Error fetching current release: %w", err)
 	}
-	return rel.Manifest, true, nil
+	return rel, nil
+}
+
+// deploymentIDFromRelease extracts the deployment id encoded in a release's
+// chart version. BuildAppChart writes the chart version as "0.0.<id>"
+// (chart.go); the parsed id lets CommandPreview pin the previewed manifests
+// to the currently-deployed value so the `app.kubernetes.io/version`
+// annotation does not churn in the diff. Returns 0 when the version does not
+// match the expected shape - the caller then falls back to the timestamp.
+func deploymentIDFromRelease(rel *release.Release) int64 {
+	if rel == nil || rel.Chart == nil || rel.Chart.Metadata == nil {
+		return 0
+	}
+	const prefix = "0.0."
+	v := rel.Chart.Metadata.Version
+	if !strings.HasPrefix(v, prefix) {
+		return 0
+	}
+	id, err := strconv.ParseInt(strings.TrimPrefix(v, prefix), 10, 64)
+	if err != nil {
+		return 0
+	}
+	return id
 }
 
 func renderUpgradeDryRun(ctx context.Context, helmAgent *HelmAgent, chartResult BuildResult, chartRequested *chart.Chart) (string, error) {

plugins/scheduler-k3s/triggers.go

@@ -476,7 +476,7 @@ func TriggerSchedulerDeploy(scheduler string, appName string, imageTag string) e
 		return fmt.Errorf("Error creating kubernetes namespace for deployment: %w", err)
 	}
 
-	chartResult, err := BuildAppChart(ctx, appName, imageTag)
+	chartResult, err := BuildAppChart(ctx, appName, imageTag, BuildOptions{})
 	if err != nil {
 		return err
 	}