Implement manual rollback from list of agent installs

Author: pchila

internal/pkg/agent/application/upgrade/manual_rollback.go

@@ -9,15 +9,19 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/elastic/elastic-agent/internal/pkg/agent/application/filelock"
 	"github.com/elastic/elastic-agent/internal/pkg/agent/application/paths"
 	"github.com/elastic/elastic-agent/internal/pkg/agent/application/reexec"
+	"github.com/elastic/elastic-agent/internal/pkg/agent/application/upgrade/details"
 	"github.com/elastic/elastic-agent/internal/pkg/fleetapi"
+	"github.com/elastic/elastic-agent/internal/pkg/release"
 	v1 "github.com/elastic/elastic-agent/pkg/api/v1"
 	"github.com/elastic/elastic-agent/pkg/core/logger"
 	"github.com/elastic/elastic-agent/pkg/version"
+	agtversion "github.com/elastic/elastic-agent/version"
 )
 
 func (u *Upgrader) rollbackToPreviousVersion(ctx context.Context, topDir string, now time.Time, version string, action *fleetapi.ActionUpgrade) (reexec.ShutdownCallbackFn, error) {
@@ -37,7 +41,7 @@ func (u *Upgrader) rollbackToPreviousVersion(ctx context.Context, topDir string,
 
 	if errors.Is(err, os.ErrNotExist) {
 		// there is no upgrade marker, we need to extract available rollbacks from agent installs
-		watcherExecutable, versionedHomeToRollbackTo, err = rollbackUsingAgentInstalls()
+		watcherExecutable, versionedHomeToRollbackTo, err = rollbackUsingAgentInstalls(ctx, u.log, u.watcherHelper, u.installDescriptorSource, topDir, now, version, u.markUpgrade)
 	} else {
 		watcherExecutable, versionedHomeToRollbackTo, err = rollbackUsingUpgradeMarker(ctx, u.log, u.watcherHelper, topDir, now, version)
 	}
@@ -56,10 +60,69 @@ func (u *Upgrader) rollbackToPreviousVersion(ctx context.Context, topDir string,
 	return nil, nil
 }
 
-func rollbackUsingAgentInstalls() (string, string, error) {
+func rollbackUsingAgentInstalls(ctx context.Context, log *logger.Logger, watcherHelper WatcherHelper, source installDescriptorSource, topDir string, now time.Time, rollbackVersion string, markUpgrade markUpgradeFunc) (string, string, error) {
 	//FIXME implement
 	//panic("Not implemented")
-	return "", "", errors.Join(errors.New("not implemented"), os.ErrNotExist)
+	//return "", "", errors.Join(errors.New("not implemented"), os.ErrNotExist)
+
+	// read the available installs
+	installDescriptor, err := source.GetInstallDesc()
+	if err != nil {
+		return "", "", fmt.Errorf("retrieving agent installs: %w", err)
+	}
+	// check for the version we want to rollback to
+	found := false
+	var targetInstall v1.AgentInstallDesc
+	for _, i := range installDescriptor.AgentInstalls {
+		if i.TTL == nil {
+			// valid rollbacks should have a TTL associated
+			continue
+		}
+		if i.Version == rollbackVersion && now.Before(*i.TTL) {
+			// found a valid target
+			found = true
+			targetInstall = i
+			break
+		}
+	}
+
+	if !found {
+		return "", "", fmt.Errorf("version %q not listed among the available rollbacks: %w", rollbackVersion, ErrNoRollbacksAvailable)
+	}
+
+	prevAgentParsedVersion, err := version.ParseVersion(targetInstall.Version)
+	if err != nil {
+		return "", "", fmt.Errorf("parsing version of target install %+v: %w", targetInstall, err)
+	}
+
+	// write out a fake upgrade marker to make the upgrade details state happy
+	relCurVersionedHome, err := filepath.Rel(paths.Top(), paths.Home())
+	if err != nil {
+		return "", "", fmt.Errorf("getting current install home path %q relative to top %q: %w", paths.Home(), paths.Top(), err)
+	}
+	curAgentInstall := agentInstall{
+		parsedVersion: agtversion.GetParsedAgentPackageVersion(),
+		version:       release.VersionWithSnapshot(),
+		hash:          release.Commit(),
+		versionedHome: relCurVersionedHome,
+	}
+
+	prevAgentInstall := agentInstall{
+		parsedVersion: prevAgentParsedVersion,
+		version:       targetInstall.Version,
+		hash:          targetInstall.Hash,
+		versionedHome: targetInstall.VersionedHome,
+	}
+
+	upgradeDetails := details.NewDetails(release.VersionWithSnapshot(), details.StateRequested, "" /*action.ID*/)
+	err = markUpgrade(log, paths.DataFrom(topDir), now, curAgentInstall, prevAgentInstall, nil /*action*/, upgradeDetails, nil)
+	if err != nil {
+		return "", "", fmt.Errorf("creating upgrade marker: %w", err)
+	}
+
+	// return watcher executable and versionedHome to rollback to
+	watcherExecutable := watcherHelper.SelectWatcherExecutable(topDir, prevAgentInstall, curAgentInstall)
+	return watcherExecutable, targetInstall.VersionedHome, nil
 }
 
 func rollbackUsingUpgradeMarker(ctx context.Context, log *logger.Logger, watcherHelper WatcherHelper, topDir string, now time.Time, version string) (string, string, error) {

internal/pkg/agent/application/upgrade/upgrade.go

@@ -121,6 +121,7 @@ type installDescriptorSource interface {
 	AddInstallDesc(desc v1.AgentInstallDesc) (*v1.InstallDescriptor, error)
 	ModifyInstallDesc(modifierFunc func(desc *v1.AgentInstallDesc) error) (*v1.InstallDescriptor, error)
 	RemoveAgentInstallDesc(versionedHome string) (*v1.InstallDescriptor, error)
+	GetInstallDesc() (*v1.InstallDescriptor, error)
 }
 
 // Upgrader performs an upgrade

pkg/utils/install/file_source.go

@@ -22,6 +22,10 @@ func NewFileDescriptorSource(descriptorFile string) *FileDescriptorSource {
 	return &FileDescriptorSource{descriptorFile: descriptorFile}
 }
 
+func (dp *FileDescriptorSource) GetInstallDesc() (*v1.InstallDescriptor, error) {
+	return readInstallMarkerFile(dp.descriptorFile)
+}
+
 func (dp *FileDescriptorSource) AddInstallDesc(desc v1.AgentInstallDesc) (*v1.InstallDescriptor, error) {
 	installDescriptor, err := readInstallMarkerFile(dp.descriptorFile)
 	// not existing or empty files are tolerated, since we would be writing a new descriptor, return any other error