Expose parallelism semaphore in the cli ui as -parallelism=#

command/apply.go

@@ -38,6 +38,7 @@ func (c *ApplyCommand) Run(args []string) int {
 		cmdFlags.BoolVar(&destroyForce, "force", false, "force")
 	}
 	cmdFlags.BoolVar(&refresh, "refresh", true, "refresh")
+	cmdFlags.IntVar(&c.Meta.parallelism, "parallelism", 0, "parallelism")
 	cmdFlags.StringVar(&c.Meta.statePath, "state", DefaultStateFilename, "path")
 	cmdFlags.StringVar(&c.Meta.stateOutPath, "state-out", "", "path")
 	cmdFlags.StringVar(&c.Meta.backupPath, "backup", "", "path")
@@ -93,9 +94,10 @@ func (c *ApplyCommand) Run(args []string) int {
 
 	// Build the context based on the arguments given
 	ctx, planned, err := c.Context(contextOpts{
-		Destroy:   c.Destroy,
-		Path:      configPath,
-		StatePath: c.Meta.statePath,
+		Destroy:     c.Destroy,
+		Path:        configPath,
+		StatePath:   c.Meta.statePath,
+		Parallelism: c.Meta.parallelism,
 	})
 	if err != nil {
 		c.Ui.Error(err.Error())
@@ -305,6 +307,8 @@ Options:
 
   -no-color              If specified, output won't contain any color.
 
+  -parallelism=#         Limit the number of concurrent operations.
+
   -refresh=true          Update state prior to checking for differences. This
                          has no effect if a plan file is given to apply.
 

command/apply_test.go

@@ -58,6 +58,82 @@ func TestApply(t *testing.T) {
 	}
 }
 
+func TestApply_parallelism1(t *testing.T) {
+	statePath := testTempFile(t)
+
+	ui := new(cli.MockUi)
+	p := testProvider()
+	pr := new(terraform.MockResourceProvisioner)
+
+	pr.ApplyFn = func(*terraform.InstanceState, *terraform.ResourceConfig) error {
+		time.Sleep(time.Second)
+		return nil
+	}
+
+	args := []string{
+		"-state", statePath,
+		"-parallelism=1",
+		testFixturePath("parallelism"),
+	}
+
+	c := &ApplyCommand{
+		Meta: Meta{
+			ContextOpts: testCtxConfigWithShell(p, pr),
+			Ui:          ui,
+		},
+	}
+
+	start := time.Now()
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
+	}
+	elapsed := time.Since(start).Seconds()
+
+	// This test should take exactly two seconds, plus some minor amount of execution time.
+	if elapsed < 2 || elapsed > 2.2 {
+		t.Fatalf("bad: %f\n\n%s", elapsed, ui.ErrorWriter.String())
+	}
+
+}
+
+func TestApply_parallelism2(t *testing.T) {
+	statePath := testTempFile(t)
+
+	ui := new(cli.MockUi)
+	p := testProvider()
+	pr := new(terraform.MockResourceProvisioner)
+
+	pr.ApplyFn = func(*terraform.InstanceState, *terraform.ResourceConfig) error {
+		time.Sleep(time.Second)
+		return nil
+	}
+
+	args := []string{
+		"-state", statePath,
+		"-parallelism=2",
+		testFixturePath("parallelism"),
+	}
+
+	c := &ApplyCommand{
+		Meta: Meta{
+			ContextOpts: testCtxConfigWithShell(p, pr),
+			Ui:          ui,
+		},
+	}
+
+	start := time.Now()
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
+	}
+	elapsed := time.Since(start).Seconds()
+
+	// This test should take exactly one second, plus some minor amount of execution time.
+	if elapsed < 1 || elapsed > 1.2 {
+		t.Fatalf("bad: %f\n\n%s", elapsed, ui.ErrorWriter.String())
+	}
+
+}
+
 func TestApply_configInvalid(t *testing.T) {
 	p := testProvider()
 	ui := new(cli.MockUi)

command/command_test.go

@@ -52,6 +52,21 @@ func testCtxConfig(p terraform.ResourceProvider) *terraform.ContextOpts {
 	}
 }
 
+func testCtxConfigWithShell(p terraform.ResourceProvider, pr terraform.ResourceProvisioner) *terraform.ContextOpts {
+	return &terraform.ContextOpts{
+		Providers: map[string]terraform.ResourceProviderFactory{
+			"test": func() (terraform.ResourceProvider, error) {
+				return p, nil
+			},
+		},
+		Provisioners: map[string]terraform.ResourceProvisionerFactory{
+			"shell": func() (terraform.ResourceProvisioner, error) {
+				return pr, nil
+			},
+		},
+	}
+}
+
 func testModule(t *testing.T, name string) *module.Tree {
 	mod, err := module.NewTreeModule("", filepath.Join(fixtureDir, name))
 	if err != nil {

command/meta.go

@@ -59,9 +59,13 @@ type Meta struct {
 	//
 	// backupPath is used to backup the state file before writing a modified
 	// version. It defaults to stateOutPath + DefaultBackupExtention
+	//
+	// parallelism is used to control the number of concurrent operations
+	// allowed when walking the graph
 	statePath    string
 	stateOutPath string
 	backupPath   string
+	parallelism  int
 }
 
 // initStatePaths is used to initialize the default values for
@@ -151,6 +155,7 @@ func (m *Meta) Context(copts contextOpts) (*terraform.Context, bool, error) {
 	}
 
 	opts.Module = mod
+	opts.Parallelism = copts.Parallelism
 	opts.State = state.State()
 	ctx := terraform.NewContext(opts)
 	return ctx, false, nil
@@ -429,4 +434,7 @@ type contextOpts struct {
 
 	// Set to true when running a destroy plan/apply.
 	Destroy bool
+
+	// Number of concurrent operations allowed
+	Parallelism int
 }

command/plan.go

@@ -27,6 +27,7 @@ func (c *PlanCommand) Run(args []string) int {
 	cmdFlags.BoolVar(&refresh, "refresh", true, "refresh")
 	c.addModuleDepthFlag(cmdFlags, &moduleDepth)
 	cmdFlags.StringVar(&outPath, "out", "", "path")
+	cmdFlags.IntVar(&c.Meta.parallelism, "parallelism", 0, "parallelism")
 	cmdFlags.StringVar(&c.Meta.statePath, "state", DefaultStateFilename, "path")
 	cmdFlags.StringVar(&c.Meta.backupPath, "backup", "", "path")
 	cmdFlags.BoolVar(&detailed, "detailed-exitcode", false, "detailed-exitcode")
@@ -54,9 +55,10 @@ func (c *PlanCommand) Run(args []string) int {
 	}
 
 	ctx, _, err := c.Context(contextOpts{
-		Destroy:   destroy,
-		Path:      path,
-		StatePath: c.Meta.statePath,
+		Destroy:     destroy,
+		Path:        path,
+		StatePath:   c.Meta.statePath,
+		Parallelism: c.Meta.parallelism,
 	})
 	if err != nil {
 		c.Ui.Error(err.Error())

command/refresh.go

@@ -18,6 +18,7 @@ func (c *RefreshCommand) Run(args []string) int {
 
 	cmdFlags := c.Meta.flagSet("refresh")
 	cmdFlags.StringVar(&c.Meta.statePath, "state", DefaultStateFilename, "path")
+	cmdFlags.IntVar(&c.Meta.parallelism, "parallelism", 0, "parallelism")
 	cmdFlags.StringVar(&c.Meta.stateOutPath, "state-out", "", "path")
 	cmdFlags.StringVar(&c.Meta.backupPath, "backup", "", "path")
 	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
@@ -78,8 +79,9 @@ func (c *RefreshCommand) Run(args []string) int {
 
 	// Build the context based on the arguments given
 	ctx, _, err := c.Context(contextOpts{
-		Path:      configPath,
-		StatePath: c.Meta.statePath,
+		Path:        configPath,
+		StatePath:   c.Meta.statePath,
+		Parallelism: c.Meta.parallelism,
 	})
 	if err != nil {
 		c.Ui.Error(err.Error())

command/test-fixtures/parallelism/main.tf

@@ -0,0 +1,13 @@
+resource "test_instance" "foo1" {
+	ami = "bar"
+
+	// shell has been configured to sleep for one second
+	provisioner "shell" {}
+}
+
+resource "test_instance" "foo2" {
+	ami = "bar"
+
+	// shell has been configured to sleep for one second
+	provisioner "shell" {}
+}