add install descriptor during initial install

Author: pchila

internal/pkg/agent/cmd/run.go

@@ -723,7 +723,7 @@ func ensureInstallMarkerPresent() error {
 	if err != nil {
 		return fmt.Errorf("failed to get current file owner: %w", err)
 	}
-	if err := install.CreateInstallMarker(paths.Top(), ownership); err != nil {
+	if err := install.CreateInstallMarker(paths.Top(), ownership, paths.Home(), version.GetAgentPackageVersion()); err != nil {
 		return fmt.Errorf("unable to create installation marker file during upgrade: %w", err)
 	}
 

internal/pkg/agent/install/install.go

@@ -17,6 +17,7 @@ import (
 	"github.com/kardianos/service"
 	"github.com/otiai10/copy"
 	"github.com/schollz/progressbar/v3"
+	"gopkg.in/yaml.v3"
 
 	"github.com/elastic/elastic-agent-libs/logp"
 	"github.com/elastic/elastic-agent/internal/pkg/agent/application/paths"
@@ -25,6 +26,7 @@ import (
 	"github.com/elastic/elastic-agent/internal/pkg/cli"
 	v1 "github.com/elastic/elastic-agent/pkg/api/v1"
 	"github.com/elastic/elastic-agent/pkg/utils"
+	manifestutils "github.com/elastic/elastic-agent/pkg/utils/manifest"
 )
 
 const (
@@ -61,17 +63,20 @@ func Install(cfgFile, topPath string, unprivileged bool, log *logp.Logger, pt *p
 		}
 	}
 
-	err = setupInstallPath(topPath, ownership)
-	if err != nil {
-		return utils.FileOwner{}, fmt.Errorf("error setting up install path: %w", err)
-	}
-
 	manifest, err := readPackageManifest(dir)
 	if err != nil {
 		return utils.FileOwner{}, fmt.Errorf("reading package manifest: %w", err)
 	}
 
 	pathMappings := manifest.Package.PathMappings
+	pathMapper := manifestutils.NewPathMapper(pathMappings)
+
+	targetVersionedHome := filepath.FromSlash(pathMapper.Map(manifest.Package.VersionedHome))
+
+	err = setupInstallPath(topPath, ownership, targetVersionedHome, manifest.Package.Version)
+	if err != nil {
+		return utils.FileOwner{}, fmt.Errorf("error setting up install path: %w", err)
+	}
 
 	pt.Describe("Copying install files")
 	copyConcurrency := calculateCopyConcurrency(streams)
@@ -184,7 +189,7 @@ func Install(cfgFile, topPath string, unprivileged bool, log *logp.Logger, pt *p
 }
 
 // setup the basic topPath, and the .installed file
-func setupInstallPath(topPath string, ownership utils.FileOwner) error {
+func setupInstallPath(topPath string, ownership utils.FileOwner, versionedHome string, version string) error {
 	// ensure parent directory exists
 	err := os.MkdirAll(filepath.Dir(topPath), 0755)
 	if err != nil {
@@ -198,7 +203,7 @@ func setupInstallPath(topPath string, ownership utils.FileOwner) error {
 	}
 
 	// create the install marker
-	if err := CreateInstallMarker(topPath, ownership); err != nil {
+	if err := CreateInstallMarker(topPath, ownership, versionedHome, version); err != nil {
 		return fmt.Errorf("failed to create install marker: %w", err)
 	}
 	return nil
@@ -516,16 +521,32 @@ func hasAllSSDs(block ghw.BlockInfo) bool {
 
 // CreateInstallMarker creates a `.installed` file at the given install path,
 // and then calls fixInstallMarkerPermissions to set the ownership provided by `ownership`
-func CreateInstallMarker(topPath string, ownership utils.FileOwner) error {
+func CreateInstallMarker(topPath string, ownership utils.FileOwner, home string, version string) error {
 	markerFilePath := filepath.Join(topPath, paths.MarkerFileName)
-	handle, err := os.Create(markerFilePath)
+	err := createInstallMarkerFile(markerFilePath, version, home)
 	if err != nil {
-		return err
+		return fmt.Errorf("creating install marker: %w", err)
 	}
-	_ = handle.Close()
 	return fixInstallMarkerPermissions(markerFilePath, ownership)
 }
 
+func createInstallMarkerFile(markerFilePath string, version string, home string) error {
+	handle, err := os.Create(markerFilePath)
+	if err != nil {
+		return fmt.Errorf("creating destination file %q : %w", markerFilePath, err)
+	}
+	defer func() {
+		_ = handle.Close()
+	}()
+	installDescriptor := v1.NewInstallDescriptor()
+	installDescriptor.AgentInstalls = []v1.AgentInstallDesc{{Version: version, VersionedHome: home}}
+	err = yaml.NewEncoder(handle).Encode(installDescriptor)
+	if err != nil {
+		return fmt.Errorf("writing install descriptor: %w", err)
+	}
+	return nil
+}
+
 func UnprivilegedUser(username, password string) (string, string) {
 	if username != "" {
 		return username, password

internal/pkg/agent/install/install_test.go

@@ -224,7 +224,19 @@ func TestSetupInstallPath(t *testing.T) {
 	tmpdir := t.TempDir()
 	ownership, err := utils.CurrentFileOwner()
 	require.NoError(t, err)
-	err = setupInstallPath(tmpdir, ownership)
+	err = setupInstallPath(tmpdir, ownership, "data/elastic-agent-1.2.3-SNAPSHOT", "1.2.3-SNAPSHOT")
 	require.NoError(t, err)
-	require.FileExists(t, filepath.Join(tmpdir, paths.MarkerFileName))
+	markerFilePath := filepath.Join(tmpdir, paths.MarkerFileName)
+	require.FileExists(t, markerFilePath)
+
+	const expectedInstallDescriptor = `
+        version: co.elastic.agent/v1
+        kind: InstallDescriptor
+        agentInstalls:
+            - version: 1.2.3-SNAPSHOT
+              versioned-home: data/elastic-agent-1.2.3-SNAPSHOT
+    `
+	actualInstallDescriptorBytes, err := os.ReadFile(markerFilePath)
+	require.NoError(t, err, "error reading actual install descriptor")
+	assert.YAMLEq(t, expectedInstallDescriptor, string(actualInstallDescriptorBytes), "expected and actual install descriptor do not match")
 }