[Ingest Manager] Agent atomic installer

x-pack/elastic-agent/pkg/artifact/install/atomic/atomic_installer.go

@@ -0,0 +1,62 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package atomic
+
+import (
+	"context"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+type embeddedInstaller interface {
+	Install(ctx context.Context, programName, version, installDir string) error
+}
+
+// Installer installs into temporary destination and moves to correct one after
+// successful finish.
+type Installer struct {
+	installer embeddedInstaller
+}
+
+// NewInstaller creates a new AtomicInstaller
+func NewInstaller(i embeddedInstaller) (*Installer, error) {
+	return &Installer{
+		installer: i,
+	}, nil
+}
+
+// Install performs installation of program in a specific version.
+func (i *Installer) Install(ctx context.Context, programName, version, installDir string) error {
+	// tar installer uses Dir of installDir to determine location of unpack
+	tempDir, err := ioutil.TempDir(os.TempDir(), "elastic-agent-install")
+	if err != nil {
+		return err
+	}
+	tempInstallDir := filepath.Join(tempDir, filepath.Base(installDir))
+
+	// cleanup install directory before Install
+	if _, err := os.Stat(installDir); err == nil || os.IsExist(err) {
+		os.RemoveAll(installDir)
+	}
+
+	if _, err := os.Stat(tempInstallDir); err == nil || os.IsExist(err) {
+		os.RemoveAll(tempInstallDir)
+	}
+
+	if err := i.installer.Install(ctx, programName, version, tempInstallDir); err != nil {
+		// cleanup unfinished install
+		os.RemoveAll(tempInstallDir)
+		return err
+	}
+
+	if err := os.Rename(tempInstallDir, installDir); err != nil {
+		os.RemoveAll(installDir)
+		os.RemoveAll(tempInstallDir)
+		return err
+	}
+
+	return nil
+}

x-pack/elastic-agent/pkg/artifact/install/atomic/atomic_installer_test.go

@@ -0,0 +1,115 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package atomic
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestOKInstall(t *testing.T) {
+	sig := make(chan int)
+	ti := &testInstaller{sig}
+	var wg sync.WaitGroup
+	i, err := NewInstaller(ti)
+
+	assert.NoError(t, err)
+
+	ctx := context.Background()
+	installDir := filepath.Join(os.TempDir(), "install_dir")
+
+	wg.Add(1)
+	go func() {
+		err := i.Install(ctx, "a", "b", installDir)
+		assert.NoError(t, err)
+		wg.Done()
+	}()
+
+	// signal to process next files
+	close(sig)
+
+	wg.Wait()
+
+	assert.DirExists(t, installDir)
+	files := getFiles()
+
+	for name := range files {
+		path := filepath.Join(installDir, name)
+		assert.FileExists(t, path)
+	}
+
+	os.RemoveAll(installDir)
+}
+
+func TestContextCancelledInstall(t *testing.T) {
+	sig := make(chan int)
+	ti := &testInstaller{sig}
+	var wg sync.WaitGroup
+	i, err := NewInstaller(ti)
+
+	assert.NoError(t, err)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	installDir := filepath.Join(os.TempDir(), "install_dir")
+
+	wg.Add(1)
+	go func() {
+		err := i.Install(ctx, "a", "b", installDir)
+		assert.Error(t, err)
+		wg.Done()
+	}()
+
+	// cancel before signaling
+	cancel()
+	close(sig)
+
+	wg.Wait()
+
+	assert.NoDirExists(t, installDir)
+}
+
+type testInstaller struct {
+	signal chan int
+}
+
+func (ti *testInstaller) Install(ctx context.Context, programName, version, installDir string) error {
+	files := getFiles()
+	if err := os.MkdirAll(installDir, 0777); err != nil {
+		return err
+	}
+
+	for name, content := range files {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+
+		filename := filepath.Join(installDir, name)
+		if err := ioutil.WriteFile(filename, content, 0666); err != nil {
+			return err
+		}
+
+		// wait for all but last
+		<-ti.signal
+	}
+
+	return nil
+}
+
+func getFiles() map[string][]byte {
+	files := make(map[string][]byte)
+	fileCount := 3
+	for i := 1; i <= fileCount; i++ {
+		files[fmt.Sprintf("file_%d", i)] = []byte(fmt.Sprintf("content of file %d", i))
+	}
+
+	return files
+}

x-pack/elastic-agent/pkg/artifact/install/installer.go

@@ -12,6 +12,7 @@ import (
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/artifact/install/dir"
 
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/artifact"
+	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/artifact/install/atomic"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/artifact/install/hooks"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/artifact/install/tar"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/artifact/install/zip"
@@ -60,5 +61,10 @@ func NewInstaller(config *artifact.Config) (InstallerChecker, error) {
 		return nil, err
 	}
 
-	return hooks.NewInstallerChecker(installer, dir.NewChecker())
+	atomicInstaller, err := atomic.NewInstaller(installer)
+	if err != nil {
+		return nil, err
+	}
+
+	return hooks.NewInstallerChecker(atomicInstaller, dir.NewChecker())
 }