coder · ammario · Oct 22, 2022 · Oct 21, 2022 · Oct 22, 2022
diff --git a/provisioner/terraform/install.go b/provisioner/terraform/install.go
@@ -0,0 +1,80 @@
+package terraform
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/gofrs/flock"
+	"github.com/hashicorp/go-version"
+	"github.com/hashicorp/hc-install/product"
+	"github.com/hashicorp/hc-install/releases"
+	"golang.org/x/xerrors"
+
+	"cdr.dev/slog"
+)
+
+var (
+	// TerraformVersion is the version of Terraform used internally
+	// when Terraform is not available on the system.
+	TerraformVersion = version.Must(version.NewVersion("1.3.0"))
+
+	minTerraformVersion = version.Must(version.NewVersion("1.1.0"))
+	maxTerraformVersion = version.Must(version.NewVersion("1.3.0"))
+
+	terraformMinorVersionMismatch = xerrors.New("Terraform binary minor version mismatch.")
+)
+
+// Install implements a thread-safe, idempotent Terraform Install
+// operation.
+func Install(ctx context.Context, log slog.Logger, dir string, wantVersion *version.Version) (string, error) {
+	err := os.MkdirAll(dir, 0750)
+	if err != nil {
+		return "", err
+	}
+
+	// Windows requires a separate lock file.
+	// See https://github.com/pinterest/knox/blob/master/client/flock_windows.go#L64
+	// for precedent.
+	lockFilePath := filepath.Join(dir, "lock")
+	lock := flock.New(lockFilePath)
+	ok, err := lock.TryLockContext(ctx, time.Millisecond*100)
+	if !ok {
+		return "", xerrors.Errorf("could not acquire flock for %v: %w", lockFilePath, err)
+	}
+	defer lock.Close()
+
+	binPath := filepath.Join(dir, product.Terraform.BinaryName())
+
+	hasVersion, err := versionFromBinaryPath(ctx, binPath)
+	if err == nil && hasVersion.Equal(wantVersion) {
+		return binPath, err
+	}
+
+	installer := &releases.ExactVersion{
+		InstallDir: dir,
+		Product:    product.Terraform,
+		Version:    TerraformVersion,
+	}
+	installer.SetLogger(slog.Stdlib(ctx, log, slog.LevelDebug))
+	log.Debug(
+		ctx,
+		"installing terraform",
+		slog.F("dir", dir),
+		slog.F("version", TerraformVersion),
+	)
+
+	path, err := installer.Install(ctx)
+	if err != nil {
+		return "", xerrors.Errorf("install: %w", err)
+	}
+
+	// Sanity-check: if path != binPath then future invocations of Install
+	// will fail.
+	if path != binPath {
+		return "", xerrors.Errorf("%s should be %s", path, binPath)
+	}
+
+	return path, nil
+}
diff --git a/provisioner/terraform/install_test.go b/provisioner/terraform/install_test.go
@@ -0,0 +1,71 @@
+package terraform_test
+
+import (
+	"context"
+	"os"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/hashicorp/go-version"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"cdr.dev/slog/sloggers/slogtest"
+	"github.com/coder/coder/provisioner/terraform"
+)
+
+func TestInstall(t *testing.T) {
+	t.Parallel()
+	ctx := context.Background()
+	dir := t.TempDir()
+	log := slogtest.Make(t, nil)
+
+	// install spins off 8 installs with Version and waits for them all
+	// to complete.
+	install := func(version *version.Version) string {
+		var wg sync.WaitGroup
+		var path atomic.Pointer[string]
+		for i := 0; i < 8; i++ {
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
+				p, err := terraform.Install(ctx, log, dir, version)
+				assert.NoError(t, err)
+				path.Store(&p)
+			}()
+		}
+		wg.Wait()
+		if t.Failed() {
+			t.FailNow()
+		}
+		return *path.Load()
+	}
+
+	binPath := install(terraform.TerraformVersion)
+
+	checkBin := func() time.Time {
+		binInfo, err := os.Stat(binPath)
+		require.NoError(t, err)
+		require.Greater(t, binInfo.Size(), int64(0))
+		return binInfo.ModTime()
+	}
+
+	firstMod := checkBin()
+
+	// Since we're using the same version the install should be idempotent.
+	install(terraform.TerraformVersion)
+	secondMod := checkBin()
+	require.Equal(t, firstMod, secondMod)
+
+	// Ensure a new install happens when version changes
+	differentVersion := version.Must(version.NewVersion("1.2.0"))
+	// Sanity-check
+	require.NotEqual(t, differentVersion.String(), terraform.TerraformVersion.String())
+
+	install(differentVersion)
+
+	thirdMod := checkBin()
+	require.Greater(t, thirdMod, secondMod)
+}
diff --git a/provisioner/terraform/provision_test.go b/provisioner/terraform/provision_test.go
@@ -5,6 +5,7 @@ package terraform_test
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -43,7 +44,9 @@ func setupProvisioner(t *testing.T, opts *provisionerServeOptions) (context.Cont
 		_ = server.Close()
 		cancelFunc()
 		err := <-serverErr
-		assert.NoError(t, err)
+		if !errors.Is(err, context.Canceled) {
+			assert.NoError(t, err)
+		}
 	})
 	go func() {
 		serverErr <- terraform.Serve(ctx, &terraform.ServeOptions{

diff --git a/provisioner/terraform/serve.go b/provisioner/terraform/serve.go
@@ -7,31 +7,12 @@ import (
 	"time"
 
 	"github.com/cli/safeexec"
-	"github.com/hashicorp/go-version"
-	"github.com/hashicorp/hc-install/product"
-	"github.com/hashicorp/hc-install/releases"
 	"golang.org/x/xerrors"
 
 	"cdr.dev/slog"
 	"github.com/coder/coder/provisionersdk"
 )
 
-var (
-	// TerraformVersion is the version of Terraform used internally
-	// when Terraform is not available on the system.
-	TerraformVersion = version.Must(version.NewVersion("1.3.0"))
-
-	minTerraformVersion = version.Must(version.NewVersion("1.1.0"))
-	maxTerraformVersion = version.Must(version.NewVersion("1.3.0"))
-
-	terraformMinorVersionMismatch = xerrors.New("Terraform binary minor version mismatch.")
-
-	installTerraform         sync.Once
-	installTerraformExecPath string
-	// nolint:errname
-	installTerraformError error
-)
-
 const (
 	defaultExitTimeout = 5 * time.Minute
 )
@@ -98,21 +79,11 @@ func Serve(ctx context.Context, options *ServeOptions) error {
 				return xerrors.Errorf("absolute binary context canceled: %w", err)
 			}
 
-			// We don't want to install Terraform multiple times!
-			installTerraform.Do(func() {
-				installer := &releases.ExactVersion{
-					InstallDir: options.CachePath,
-					Product:    product.Terraform,
-					Version:    TerraformVersion,
-				}
-				installer.SetLogger(slog.Stdlib(ctx, options.Logger, slog.LevelDebug))
-				options.Logger.Debug(ctx, "installing terraform", slog.F("dir", options.CachePath), slog.F("version", TerraformVersion))
-				installTerraformExecPath, installTerraformError = installer.Install(ctx)
-			})
-			if installTerraformError != nil {
-				return xerrors.Errorf("install terraform: %w", installTerraformError)
+			binPath, err := Install(ctx, options.Logger, options.CachePath, TerraformVersion)
+			if err != nil {
+				return xerrors.Errorf("install terraform: %w", err)
 			}
-			options.BinaryPath = installTerraformExecPath
+			options.BinaryPath = binPath
 		} else {
 			options.BinaryPath = absoluteBinary
 		}