[Builder|Build|PostProcessor|Provisioner|Hook]Server: context cancel using a RPC cancel method

common/step_provision.go

@@ -50,6 +50,9 @@ func (s *StepProvision) Run(ctx context.Context, state multistep.StateBag) multi
 			}
 
 			return multistep.ActionContinue
+		case <-ctx.Done():
+			log.Printf("Cancelling provisioning due to context cancellation: %s", ctx.Err())
+			return multistep.ActionHalt
 		case <-time.After(1 * time.Second):
 			if _, ok := state.GetOk(multistep.StateCancelled); ok {
 				log.Println("Cancelling provisioning due to interrupt...")

helper/multistep/basic_runner.go

@@ -20,14 +20,11 @@ type BasicRunner struct {
 	// modified.
 	Steps []Step
 
-	cancel context.CancelFunc
+	l     sync.Mutex
-	doneCh chan struct{}
+	state runState
-	state  runState
-	l      sync.Mutex
 }
 
 func (b *BasicRunner) Run(ctx context.Context, state StateBag) {
-	ctx, cancel := context.WithCancel(ctx)
 
 	b.l.Lock()
 	if b.state != stateIdle {
@@ -35,15 +32,11 @@ func (b *BasicRunner) Run(ctx context.Context, state StateBag) {
 	}
 
 	doneCh := make(chan struct{})
-	b.cancel = cancel
-	b.doneCh = doneCh
 	b.state = stateRunning
 	b.l.Unlock()
 
 	defer func() {
 		b.l.Lock()
-		b.cancel = nil
-		b.doneCh = nil
 		b.state = stateIdle
 		close(doneCh)
 		b.l.Unlock()
@@ -54,14 +47,16 @@ func (b *BasicRunner) Run(ctx context.Context, state StateBag) {
 	go func() {
 		select {
 		case <-ctx.Done():
-			// Flag cancel and wait for finish
 			state.Put(StateCancelled, true)
-			<-doneCh
 		case <-doneCh:
 		}
 	}()
 
 	for _, step := range b.Steps {
+		if err := ctx.Err(); err != nil {
+			state.Put(StateCancelled, true)
+			break
+		}
 		// We also check for cancellation here since we can't be sure
 		// the goroutine that is running to set it actually ran.
 		if runState(atomic.LoadInt32((*int32)(&b.state))) == stateCancelling {

helper/multistep/basic_runner_test.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"reflect"
 	"testing"
-	"time"
 )
 
 func TestBasicRunner_ImplRunner(t *testing.T) {
@@ -99,39 +98,47 @@ func TestBasicRunner_Run_Run(t *testing.T) {
 }
 
 func TestBasicRunner_Cancel(t *testing.T) {
-	ch := make(chan chan bool)
-	data := new(BasicStateBag)
-	stepA := &TestStepAcc{Data: "a"}
-	stepB := &TestStepAcc{Data: "b"}
-	stepInt := &TestStepSync{ch}
-	stepC := &TestStepAcc{Data: "c"}
 
-	r := &BasicRunner{Steps: []Step{stepA, stepB, stepInt, stepC}}
+	topCtx, topCtxCancel := context.WithCancel(context.Background())
 
-	ctx, cancel := context.WithCancel(context.Background())
+	checkCancelled := func(data StateBag) {
-
+		cancelled := data.Get(StateCancelled).(bool)
-	go r.Run(ctx, data)
+		if !cancelled {
-
+			t.Fatal("state should be cancelled")
-	// Wait until we reach the sync point
-	responseCh := <-ch
-
-	// Cancel then continue chain
-	cancelCh := make(chan bool)
-	go func() {
-		cancel()
-		cancelCh <- true
-	}()
-
-	for {
-		if _, ok := data.GetOk(StateCancelled); ok {
-			responseCh <- true
-			break
 		}
-
-		time.Sleep(10 * time.Millisecond)
 	}
 
-	<-cancelCh
+	data := new(BasicStateBag)
+	r := &BasicRunner{}
+	r.Steps = []Step{
+		&TestStepAcc{Data: "a"},
+		&TestStepAcc{Data: "b"},
+		TestStepFn{
+			run: func(ctx context.Context, sb StateBag) StepAction {
+				return ActionContinue
+			},
+			cleanup: checkCancelled,
+		},
+		TestStepFn{
+			run: func(ctx context.Context, sb StateBag) StepAction {
+				topCtxCancel()
+				<-ctx.Done()
+				return ActionContinue
+			},
+			cleanup: checkCancelled,
+		},
+		TestStepFn{
+			run: func(context.Context, StateBag) StepAction {
+				t.Fatal("I should not be called")
+				return ActionContinue
+			},
+			cleanup: func(StateBag) {
+				t.Fatal("I should not be called")
+			},
+		},
+	}
+
+	r.Run(topCtx, data)
 
 	// Test run data
 	expected := []string{"a", "b"}
@@ -148,10 +155,8 @@ func TestBasicRunner_Cancel(t *testing.T) {
 	}
 
 	// Test that it says it is cancelled
-	cancelled := data.Get(StateCancelled).(bool)
+	checkCancelled(data)
-	if !cancelled {
+
-		t.Errorf("not cancelled")
-	}
 }
 
 func TestBasicRunner_Cancel_Special(t *testing.T) {

helper/multistep/debug_runner_test.go

@@ -78,41 +78,64 @@ func TestDebugRunner_Run_Run(t *testing.T) {
 	t.Errorf("Was able to run an already running DebugRunner")
 }
 
+type TestStepFn struct {
+	run     func(context.Context, StateBag) StepAction
+	cleanup func(StateBag)
+}
+
+var _ Step = TestStepFn{}
+
+func (fn TestStepFn) Run(ctx context.Context, sb StateBag) StepAction {
+	return fn.run(ctx, sb)
+}
+
+func (fn TestStepFn) Cleanup(sb StateBag) {
+	if fn.cleanup != nil {
+		fn.cleanup(sb)
+	}
+}
 func TestDebugRunner_Cancel(t *testing.T) {
-	ch := make(chan chan bool)
-	data := new(BasicStateBag)
-	stepA := &TestStepAcc{Data: "a"}
-	stepB := &TestStepAcc{Data: "b"}
-	stepInt := &TestStepSync{ch}
-	stepC := &TestStepAcc{Data: "c"}
 
-	r := &DebugRunner{}
+	topCtx, topCtxCancel := context.WithCancel(context.Background())
-	r.Steps = []Step{stepA, stepB, stepInt, stepC}
 
-	ctx, cancel := context.WithCancel(context.Background())
+	checkCancelled := func(data StateBag) {
-
+		cancelled := data.Get(StateCancelled).(bool)
-	go r.Run(ctx, data)
+		if !cancelled {
-
+			t.Fatal("state should be cancelled")
-	// Wait until we reach the sync point
-	responseCh := <-ch
-
-	// Cancel then continue chain
-	cancelCh := make(chan bool)
-	go func() {
-		cancel()
-		cancelCh <- true
-	}()
-
-	for {
-		if _, ok := data.GetOk(StateCancelled); ok {
-			responseCh <- true
-			break
 		}
-
-		time.Sleep(10 * time.Millisecond)
 	}
 
-	<-cancelCh
+	data := new(BasicStateBag)
+	r := &DebugRunner{}
+	r.Steps = []Step{
+		&TestStepAcc{Data: "a"},
+		&TestStepAcc{Data: "b"},
+		TestStepFn{
+			run: func(ctx context.Context, sb StateBag) StepAction {
+				return ActionContinue
+			},
+			cleanup: checkCancelled,
+		},
+		TestStepFn{
+			run: func(ctx context.Context, sb StateBag) StepAction {
+				topCtxCancel()
+				<-ctx.Done()
+				return ActionContinue
+			},
+			cleanup: checkCancelled,
+		},
+		TestStepFn{
+			run: func(context.Context, StateBag) StepAction {
+				t.Fatal("I should not be called")
+				return ActionContinue
+			},
+			cleanup: func(StateBag) {
+				t.Fatal("I should not be called")
+			},
+		},
+	}
+
+	r.Run(topCtx, data)
 
 	// Test run data
 	expected := []string{"a", "b"}
@@ -129,8 +152,11 @@ func TestDebugRunner_Cancel(t *testing.T) {
 	}
 
 	// Test that it says it is cancelled
-	cancelled := data.Get(StateCancelled).(bool)
+	cancelled, ok := data.GetOk(StateCancelled)
-	if !cancelled {
+	if !ok {
+		t.Fatal("could not get state cancelled")
+	}
+	if !cancelled.(bool) {
 		t.Errorf("not cancelled")
 	}
 }

helper/multistep/multistep_test.go

@@ -58,7 +58,7 @@ func (s TestStepSync) Run(context.Context, StateBag) StepAction {
 	return ActionContinue
 }
 
-func (s TestStepSync) Cleanup(StateBag) {}
+func (s TestStepSync) Cleanup(StateBag) { close(s.Ch) }
 
 func (s TestStepWaitForever) Run(context.Context, StateBag) StepAction {
 	select {}

packer/build_test.go

@@ -371,12 +371,18 @@ func TestBuild_RunBeforePrepare(t *testing.T) {
 func TestBuild_Cancel(t *testing.T) {
 	build := testBuild()
 
-	ctx, cancel := context.WithCancel(context.Background())
+	build.Prepare()
-	cancel()
+
-	build.Run(ctx, nil)
+	topCtx, topCtxCancel := context.WithCancel(context.Background())
 
 	builder := build.builder.(*MockBuilder)
-	if !builder.CancelCalled {
+
-		t.Fatal("cancel should be called")
+	builder.RunFn = func(ctx context.Context) {
+		topCtxCancel()
+	}
+
+	_, err := build.Run(topCtx, testUi())
+	if err == nil {
+		t.Fatal("build should err")
 	}
 }

packer/builder_mock.go

@@ -20,6 +20,7 @@ type MockBuilder struct {
 	RunHook       Hook
 	RunUi         Ui
 	CancelCalled  bool
+	RunFn         func(ctx context.Context)
 }
 
 func (tb *MockBuilder) Prepare(config ...interface{}) ([]string, error) {
@@ -40,6 +41,9 @@ func (tb *MockBuilder) Run(ctx context.Context, ui Ui, h Hook) (Artifact, error)
 	if tb.RunNilResult {
 		return nil, nil
 	}
+	if tb.RunFn != nil {
+		tb.RunFn(ctx)
+	}
 
 	if h != nil {
 		if err := h.Run(ctx, HookProvision, ui, new(MockCommunicator), nil); err != nil {

packer/hook_mock.go

@@ -2,31 +2,21 @@ package packer
 
 import (
 	"context"
-	"time"
 )
 
 // MockHook is an implementation of Hook that can be used for tests.
 type MockHook struct {
-	RunFunc func() error
+	RunFunc func(context.Context) error
 
-	RunCalled    bool
+	RunCalled bool
-	RunComm      Communicator
+	RunComm   Communicator
-	RunData      interface{}
+	RunData   interface{}
-	RunName      string
+	RunName   string
-	RunUi        Ui
+	RunUi     Ui
-	CancelCalled bool
 }
 
 func (t *MockHook) Run(ctx context.Context, name string, ui Ui, comm Communicator, data interface{}) error {
 
-	go func() {
-		select {
-		case <-time.After(2 * time.Minute):
-		case <-ctx.Done():
-			t.CancelCalled = true
-		}
-	}()
-
 	t.RunCalled = true
 	t.RunComm = comm
 	t.RunData = data
@@ -37,5 +27,5 @@ func (t *MockHook) Run(ctx context.Context, name string, ui Ui, comm Communicato
 		return nil
 	}
 
-	return t.RunFunc()
+	return t.RunFunc(ctx)
 }

packer/hook_test.go

@@ -2,53 +2,9 @@ package packer
 
 import (
 	"context"
-	"sync"
 	"testing"
-	"time"
 )
 
-// A helper Hook implementation for testing cancels.
-type CancelHook struct {
-	sync.Mutex
-	cancelCh chan struct{}
-	doneCh   chan struct{}
-
-	Cancelled bool
-}
-
-func (h *CancelHook) Run(ctx context.Context, _ string, _ Ui, _ Communicator, _ interface{}) error {
-	go func() {
-		select {
-		case <-time.After(2 * time.Minute):
-		case <-ctx.Done():
-			h.cancel()
-		}
-	}()
-
-	h.Lock()
-	h.cancelCh = make(chan struct{})
-	h.doneCh = make(chan struct{})
-	h.Unlock()
-
-	defer close(h.doneCh)
-
-	select {
-	case <-h.cancelCh:
-		h.Cancelled = true
-	case <-time.After(1 * time.Second):
-	}
-
-	return nil
-}
-
-func (h *CancelHook) cancel() {
-	h.Lock()
-	close(h.cancelCh)
-	h.Unlock()
-
-	<-h.doneCh
-}
-
 func TestDispatchHook_Implements(t *testing.T) {
 	var _ Hook = new(DispatchHook)
 }
@@ -78,20 +34,36 @@ func TestDispatchHook_Run(t *testing.T) {
 	}
 }
 
+// A helper Hook implementation for testing cancels.
+// Run will wait indetinitelly until ctx is cancelled.
+type CancelHook struct {
+	cancel func()
+}
+
+func (h *CancelHook) Run(ctx context.Context, _ string, _ Ui, _ Communicator, _ interface{}) error {
+	h.cancel()
+	<-ctx.Done()
+	return ctx.Err()
+}
+
 func TestDispatchHook_cancel(t *testing.T) {
-	hook := new(CancelHook)
+
+	cancelHook := new(CancelHook)
 
 	dh := &DispatchHook{
 		Mapping: map[string][]Hook{
-			"foo": {hook},
+			"foo": {cancelHook},
 		},
 	}
 	ctx, cancel := context.WithCancel(context.Background())
-	go dh.Run(ctx, "foo", nil, nil, 42)
+	cancelHook.cancel = cancel
-	time.Sleep(100 * time.Millisecond)
-	cancel()
 
-	if !hook.Cancelled {
+	errchan := make(chan error)
-		t.Fatal("hook should've cancelled")
+	go func() {
+		errchan <- dh.Run(ctx, "foo", nil, nil, 42)
+	}()
+
+	if err := <-errchan; err == nil {
+		t.Fatal("hook should've errored")
 	}
 }

packer/plugin/server.go

@@ -101,7 +101,7 @@ func Server() (*packrpc.Server, error) {
 
 	// Serve a single connection
 	log.Println("Serving a plugin connection...")
-	return packrpc.NewServer(conn), nil
+	return packrpc.NewServer(conn)
 }
 
 func serverListener(minPort, maxPort int64) (net.Listener, error) {

packer/provisioner_mock.go

@@ -2,20 +2,18 @@ package packer
 
 import (
 	"context"
-	"time"
 )
 
 // MockProvisioner is an implementation of Provisioner that can be
 // used for tests.
 type MockProvisioner struct {
-	ProvFunc func() error
+	ProvFunc func(context.Context) error
 
 	PrepCalled       bool
 	PrepConfigs      []interface{}
 	ProvCalled       bool
 	ProvCommunicator Communicator
 	ProvUi           Ui
-	CancelCalled     bool
 }
 
 func (t *MockProvisioner) Prepare(configs ...interface{}) error {
@@ -25,14 +23,6 @@ func (t *MockProvisioner) Prepare(configs ...interface{}) error {
 }
 
 func (t *MockProvisioner) Provision(ctx context.Context, ui Ui, comm Communicator) error {
-	go func() {
-		select {
-		case <-time.After(2 * time.Minute):
-		case <-ctx.Done():
-			t.CancelCalled = true
-		}
-	}()
-
 	t.ProvCalled = true
 	t.ProvCommunicator = comm
 	t.ProvUi = ui
@@ -41,7 +31,7 @@ func (t *MockProvisioner) Provision(ctx context.Context, ui Ui, comm Communicato
 		return nil
 	}
 
-	return t.ProvFunc()
+	return t.ProvFunc(ctx)
 }
 
 func (t *MockProvisioner) Communicator() Communicator {

packer/provisioner_test.go

@@ -2,7 +2,6 @@ package packer
 
 import (
 	"context"
-	"sync"
 	"testing"
 	"time"
 )
@@ -63,18 +62,13 @@ func TestProvisionHook_nilComm(t *testing.T) {
 }
 
 func TestProvisionHook_cancel(t *testing.T) {
-	var lock sync.Mutex
+	topCtx, topCtxCancel := context.WithCancel(context.Background())
-	order := make([]string, 0, 2)
 
 	p := &MockProvisioner{
-		ProvFunc: func() error {
+		ProvFunc: func(ctx context.Context) error {
-			time.Sleep(100 * time.Millisecond)
+			topCtxCancel()
-
+			<-ctx.Done()
-			lock.Lock()
+			return ctx.Err()
-			defer lock.Unlock()
-			order = append(order, "prov")
-
-			return nil
 		},
 	}
 
@@ -83,27 +77,10 @@ func TestProvisionHook_cancel(t *testing.T) {
 			{p, nil, ""},
 		},
 	}
-	ctx, cancel := context.WithCancel(context.Background())
 
-	finished := make(chan struct{})
+	err := hook.Run(topCtx, "foo", nil, new(MockCommunicator), nil)
-	go func() {
+	if err == nil {
-		hook.Run(ctx, "foo", nil, new(MockCommunicator), nil)
+		t.Fatal("should have err")
-		close(finished)
-	}()
-
-	// Cancel it while it is running
-	time.Sleep(10 * time.Millisecond)
-	cancel()
-	lock.Lock()
-	order = append(order, "cancel")
-	lock.Unlock()
-
-	// Wait
-	<-finished
-
-	// Verify order
-	if len(order) != 2 || order[0] != "cancel" || order[1] != "prov" {
-		t.Fatalf("bad: %#v", order)
 	}
 }
 
@@ -156,7 +133,7 @@ func TestPausedProvisionerProvision_waits(t *testing.T) {
 	}
 
 	dataCh := make(chan struct{})
-	mock.ProvFunc = func() error {
+	mock.ProvFunc = func(context.Context) error {
 		close(dataCh)
 		return nil
 	}
@@ -177,28 +154,22 @@ func TestPausedProvisionerProvision_waits(t *testing.T) {
 }
 
 func TestPausedProvisionerCancel(t *testing.T) {
+	topCtx, cancelTopCtx := context.WithCancel(context.Background())
+
 	mock := new(MockProvisioner)
 	prov := &PausedProvisioner{
 		Provisioner: mock,
 	}
 
-	provCh := make(chan struct{})
+	mock.ProvFunc = func(ctx context.Context) error {
-	mock.ProvFunc = func() error {
+		cancelTopCtx()
-		close(provCh)
+		<-ctx.Done()
-		time.Sleep(10 * time.Millisecond)
+		return ctx.Err()
-		return nil
 	}
-	ctx, cancel := context.WithCancel(context.Background())
 
-	// Start provisioning and wait for it to start
+	err := prov.Provision(topCtx, testUi(), new(MockCommunicator))
-	go func() {
+	if err == nil {
-		<-provCh
+		t.Fatal("should have err")
-		cancel()
-	}()
-
-	prov.Provision(ctx, testUi(), new(MockCommunicator))
-	if !mock.CancelCalled {
-		t.Fatal("cancel should be called")
 	}
 }
 
@@ -243,27 +214,21 @@ func TestDebuggedProvisionerProvision(t *testing.T) {
 }
 
 func TestDebuggedProvisionerCancel(t *testing.T) {
+	topCtx, topCtxCancel := context.WithCancel(context.Background())
+
 	mock := new(MockProvisioner)
 	prov := &DebuggedProvisioner{
 		Provisioner: mock,
 	}
 
-	provCh := make(chan struct{})
+	mock.ProvFunc = func(ctx context.Context) error {
-	mock.ProvFunc = func() error {
+		topCtxCancel()
-		close(provCh)
+		<-ctx.Done()
-		time.Sleep(10 * time.Millisecond)
+		return ctx.Err()
-		return nil
 	}
-	ctx, cancel := context.WithCancel(context.Background())
 
-	// Start provisioning and wait for it to start
+	err := prov.Provision(topCtx, testUi(), new(MockCommunicator))
-	go func() {
+	if err == nil {
-		<-provCh
+		t.Fatal("should have error")
-		cancel()
-	}()
-
-	prov.Provision(ctx, testUi(), new(MockCommunicator))
-	if !mock.CancelCalled {
-		t.Fatal("cancel should be called")
 	}
 }

packer/rpc/build.go

@@ -2,6 +2,7 @@ package rpc
 
 import (
 	"context"
+	"log"
 	"net/rpc"
 
 	"github.com/hashicorp/packer/packer"
@@ -17,6 +18,9 @@ type build struct {
 // BuildServer wraps a packer.Build implementation and makes it exportable
 // as part of a Golang RPC server.
 type BuildServer struct {
+	context       context.Context
+	contextCancel func()
+
 	build packer.Build
 	mux   *muxBroker
 }
@@ -50,6 +54,19 @@ func (b *build) Run(ctx context.Context, ui packer.Ui) ([]packer.Artifact, error
 	server.RegisterUi(ui)
 	go server.Serve()
 
+	done := make(chan interface{})
+	defer close(done)
+	go func() {
+		select {
+		case <-ctx.Done():
+			log.Printf("Cancelling build after context cancellation %v", ctx.Err())
+			if err := b.client.Call("Build.Cancel", new(interface{}), new(interface{})); err != nil {
+				log.Printf("Error cancelling builder: %s", err)
+			}
+		case <-done:
+		}
+	}()
+
 	var result []uint32
 	if err := b.client.Call("Build.Run", nextId, &result); err != nil {
 		return nil, err
@@ -106,14 +123,18 @@ func (b *BuildServer) Prepare(args *interface{}, resp *BuildPrepareResponse) err
 	return nil
 }
 
-func (b *BuildServer) Run(ctx context.Context, streamId uint32, reply *[]uint32) error {
+func (b *BuildServer) Run(streamId uint32, reply *[]uint32) error {
+	if b.context == nil {
+		b.context, b.contextCancel = context.WithCancel(context.Background())
+	}
+
 	client, err := newClientWithMux(b.mux, streamId)
 	if err != nil {
 		return NewBasicError(err)
 	}
 	defer client.Close()
 
-	artifacts, err := b.build.Run(ctx, client.Ui())
+	artifacts, err := b.build.Run(b.context, client.Ui())
 	if err != nil {
 		return NewBasicError(err)
 	}
@@ -147,6 +168,8 @@ func (b *BuildServer) SetOnError(val *string, reply *interface{}) error {
 }
 
 func (b *BuildServer) Cancel(args *interface{}, reply *interface{}) error {
-	panic("cancel !")
+	if b.contextCancel != nil {
+		b.contextCancel()
+	}
 	return nil
 }

packer/rpc/build_test.go

@@ -15,6 +15,7 @@ type testBuild struct {
 	nameCalled       bool
 	prepareCalled    bool
 	prepareWarnings  []string
+	runFn            func(context.Context)
 	runCalled        bool
 	runUi            packer.Ui
 	setDebugCalled   bool
@@ -36,13 +37,13 @@ func (b *testBuild) Prepare() ([]string, error) {
 }
 
 func (b *testBuild) Run(ctx context.Context, ui packer.Ui) ([]packer.Artifact, error) {
-	go func() {
-		<-ctx.Done()
-		b.cancelCalled = true
-	}()
 	b.runCalled = true
 	b.runUi = ui
 
+	if b.runFn != nil {
+		b.runFn(ctx)
+	}
+
 	if b.errRunResult {
 		return nil, errors.New("foo")
 	} else {
@@ -62,10 +63,6 @@ func (b *testBuild) SetOnError(string) {
 	b.setOnErrorCalled = true
 }
 
-func (b *testBuild) Cancel() {
-	b.cancelCalled = true
-}
-
 func TestBuild(t *testing.T) {
 	b := new(testBuild)
 	client, server := testClientServer(t)
@@ -74,7 +71,7 @@ func TestBuild(t *testing.T) {
 	server.RegisterBuild(b)
 	bClient := client.Build()
 
-	ctx, cancel := context.WithCancel(context.Background())
+	ctx := context.Background()
 
 	// Test Name
 	bClient.Name()
@@ -131,12 +128,33 @@ func TestBuild(t *testing.T) {
 	if !b.setOnErrorCalled {
 		t.Fatal("should be called")
 	}
+}
 
-	// Test Cancel
+func TestBuild_cancel(t *testing.T) {
-	cancel()
+	topCtx, cancelTopCtx := context.WithCancel(context.Background())
-	if !b.cancelCalled {
+
-		t.Fatal("should be called")
+	b := new(testBuild)
+
+	done := make(chan interface{})
+	b.runFn = func(ctx context.Context) {
+		cancelTopCtx()
+		<-ctx.Done()
+		close(done)
 	}
+
+	client, server := testClientServer(t)
+	defer client.Close()
+	defer server.Close()
+	server.RegisterBuild(b)
+	bClient := client.Build()
+
+	bClient.Prepare()
+
+	ui := new(testUi)
+	bClient.Run(topCtx, ui)
+
+	// if context cancellation is not propagated, this will timeout
+	<-done
 }
 
 func TestBuildPrepare_Warnings(t *testing.T) {

packer/rpc/builder.go

@@ -2,6 +2,7 @@ package rpc
 
 import (
 	"context"
+	"log"
 	"net/rpc"
 
 	"github.com/hashicorp/packer/packer"
@@ -17,6 +18,9 @@ type builder struct {
 // BuilderServer wraps a packer.Builder implementation and makes it exportable
 // as part of a Golang RPC server.
 type BuilderServer struct {
+	context       context.Context
+	contextCancel func()
+
 	builder packer.Builder
 	mux     *muxBroker
 }
@@ -51,7 +55,21 @@ func (b *builder) Run(ctx context.Context, ui packer.Ui, hook packer.Hook) (pack
 	server.RegisterUi(ui)
 	go server.Serve()
 
+	done := make(chan interface{})
+	defer close(done)
+	go func() {
+		select {
+		case <-ctx.Done():
+			log.Printf("Cancelling builder after context cancellation %v", ctx.Err())
+			if err := b.client.Call("Builder.Cancel", new(interface{}), new(interface{})); err != nil {
+				log.Printf("Error cancelling builder: %s", err)
+			}
+		case <-done:
+		}
+	}()
+
 	var responseId uint32
+
 	if err := b.client.Call("Builder.Run", nextId, &responseId); err != nil {
 		return nil, err
 	}
@@ -77,14 +95,18 @@ func (b *BuilderServer) Prepare(args *BuilderPrepareArgs, reply *BuilderPrepareR
 	return nil
 }
 
-func (b *BuilderServer) Run(ctx context.Context, streamId uint32, reply *uint32) error {
+func (b *BuilderServer) Run(streamId uint32, reply *uint32) error {
 	client, err := newClientWithMux(b.mux, streamId)
 	if err != nil {
 		return NewBasicError(err)
 	}
 	defer client.Close()
 
-	artifact, err := b.builder.Run(ctx, client.Ui(), client.Hook())
+	if b.context == nil {
+		b.context, b.contextCancel = context.WithCancel(context.Background())
+	}
+
+	artifact, err := b.builder.Run(b.context, client.Ui(), client.Hook())
 	if err != nil {
 		return NewBasicError(err)
 	}
@@ -92,11 +114,16 @@ func (b *BuilderServer) Run(ctx context.Context, streamId uint32, reply *uint32)
 	*reply = 0
 	if artifact != nil {
 		streamId = b.mux.NextId()
-		server := newServerWithMux(b.mux, streamId)
+		artifactServer := newServerWithMux(b.mux, streamId)
-		server.RegisterArtifact(artifact)
+		artifactServer.RegisterArtifact(artifact)
-		go server.Serve()
+		go artifactServer.Serve()
 		*reply = streamId
 	}
 
 	return nil
 }
+
+func (b *BuilderServer) Cancel(args *interface{}, reply *interface{}) error {
+	b.contextCancel()
+	return nil
+}

packer/rpc/builder_test.go

@@ -127,19 +127,26 @@ func TestBuilderRun_ErrResult(t *testing.T) {
 }
 
 func TestBuilderCancel(t *testing.T) {
+	topCtx, topCtxCancel := context.WithCancel(context.Background())
+	// var runCtx context.Context
+
 	b := new(packer.MockBuilder)
+	cancelled := false
+	b.RunFn = func(ctx context.Context) {
+		topCtxCancel()
+		<-ctx.Done()
+		cancelled = true
+	}
 	client, server := testClientServer(t)
 	defer client.Close()
 	defer server.Close()
 	server.RegisterBuilder(b)
 	bClient := client.Builder()
 
-	ctx, cancel := context.WithCancel(context.Background())
+	bClient.Run(topCtx, new(testUi), new(packer.MockHook))
-	cancel()
-	bClient.Run(ctx, nil, nil)
 
-	if !b.CancelCalled {
+	if !cancelled {
-		t.Fatal("cancel should be called")
+		t.Fatal("context should have been cancelled")
 	}
 }
 

packer/rpc/client_test.go

@@ -35,7 +35,7 @@ func testConn(t *testing.T) (net.Conn, net.Conn) {
 func testClientServer(t *testing.T) (*Client, *Server) {
 	clientConn, serverConn := testConn(t)
 
-	server := NewServer(serverConn)
+	server, _ := NewServer(serverConn)
 	go server.Serve()
 
 	client, err := NewClient(clientConn)

packer/rpc/hook.go

@@ -18,6 +18,9 @@ type hook struct {
 // HookServer wraps a packer.Hook implementation and makes it exportable
 // as part of a Golang RPC server.
 type HookServer struct {
+	context       context.Context
+	contextCancel func()
+
 	hook packer.Hook
 	mux  *muxBroker
 }
@@ -35,6 +38,19 @@ func (h *hook) Run(ctx context.Context, name string, ui packer.Ui, comm packer.C
 	server.RegisterUi(ui)
 	go server.Serve()
 
+	done := make(chan interface{})
+	defer close(done)
+	go func() {
+		select {
+		case <-ctx.Done():
+			log.Printf("Cancelling hook after context cancellation %v", ctx.Err())
+			if err := h.client.Call("Hook.Cancel", new(interface{}), new(interface{})); err != nil {
+				log.Printf("Error cancelling builder: %s", err)
+			}
+		case <-done:
+		}
+	}()
+
 	args := HookRunArgs{
 		Name:     name,
 		Data:     data,
@@ -44,24 +60,27 @@ func (h *hook) Run(ctx context.Context, name string, ui packer.Ui, comm packer.C
 	return h.client.Call("Hook.Run", &args, new(interface{}))
 }
 
-func (h *hook) Cancel() {
+func (h *HookServer) Run(args *HookRunArgs, reply *interface{}) error {
-	err := h.client.Call("Hook.Cancel", new(interface{}), new(interface{}))
-	if err != nil {
-		log.Printf("Hook.Cancel error: %s", err)
-	}
-}
-
-func (h *HookServer) Run(ctx context.Context, args *HookRunArgs, reply *interface{}) error {
 	client, err := newClientWithMux(h.mux, args.StreamId)
 	if err != nil {
 		return NewBasicError(err)
 	}
 	defer client.Close()
 
-	if err := h.hook.Run(ctx, args.Name, client.Ui(), client.Communicator(), args.Data); err != nil {
+	if h.context == nil {
+		h.context, h.contextCancel = context.WithCancel(context.Background())
+	}
+	if err := h.hook.Run(h.context, args.Name, client.Ui(), client.Communicator(), args.Data); err != nil {
 		return NewBasicError(err)
 	}
 
 	*reply = nil
 	return nil
 }
+
+func (h *HookServer) Cancel(args *interface{}, reply *interface{}) error {
+	if h.contextCancel != nil {
+		h.contextCancel()
+	}
+	return nil
+}

packer/rpc/hook_test.go

@@ -2,59 +2,25 @@ package rpc
 
 import (
 	"context"
-	"reflect"
-	"sync"
 	"testing"
-	"time"
 
 	"github.com/hashicorp/packer/packer"
 )
 
-func TestHookRPC(t *testing.T) {
-	// Create the UI to test
-	h := new(packer.MockHook)
-	ctx, cancel := context.WithCancel(context.Background())
-
-	// Serve
-	client, server := testClientServer(t)
-	defer client.Close()
-	defer server.Close()
-	server.RegisterHook(h)
-	hClient := client.Hook()
-
-	// Test Run
-	ui := &testUi{}
-	hClient.Run(ctx, "foo", ui, nil, 42)
-	if !h.RunCalled {
-		t.Fatal("should be called")
-	}
-
-	// Test Cancel
-	cancel()
-	if !h.CancelCalled {
-		t.Fatal("should be called")
-	}
-}
-
 func TestHook_Implements(t *testing.T) {
 	var _ packer.Hook = new(hook)
 }
 
 func TestHook_cancelWhileRun(t *testing.T) {
-	var finishLock sync.Mutex
+	topCtx, cancelTopCtx := context.WithCancel(context.Background())
-	finishOrder := make([]string, 0, 2)
 
 	h := &packer.MockHook{
-		RunFunc: func() error {
+		RunFunc: func(ctx context.Context) error {
-			time.Sleep(100 * time.Millisecond)
+			cancelTopCtx()
-
+			<-ctx.Done()
-			finishLock.Lock()
+			return ctx.Err()
-			finishOrder = append(finishOrder, "run")
-			finishLock.Unlock()
-			return nil
 		},
 	}
-	ctx, cancel := context.WithCancel(context.Background())
 
 	// Serve
 	client, server := testClientServer(t)
@@ -64,26 +30,9 @@ func TestHook_cancelWhileRun(t *testing.T) {
 	hClient := client.Hook()
 
 	// Start the run
-	finished := make(chan struct{})
+	err := hClient.Run(topCtx, "foo", nil, nil, nil)
-	go func() {
-		hClient.Run(ctx, "foo", nil, nil, nil)
-		close(finished)
-	}()
 
-	// Cancel it pretty quickly.
+	if err == nil {
-	time.Sleep(10 * time.Millisecond)
+		t.Fatal("should have errored")
-	cancel()
-
-	finishLock.Lock()
-	finishOrder = append(finishOrder, "cancel")
-	finishLock.Unlock()
-
-	// Verify things are good
-	<-finished
-
-	// Check the results
-	expected := []string{"cancel", "run"}
-	if !reflect.DeepEqual(finishOrder, expected) {
-		t.Fatalf("bad: %#v", finishOrder)
 	}
 }

packer/rpc/post_processor.go

@@ -2,6 +2,7 @@ package rpc
 
 import (
 	"context"
+	"log"
 	"net/rpc"
 
 	"github.com/hashicorp/packer/packer"
@@ -17,6 +18,9 @@ type postProcessor struct {
 // PostProcessorServer wraps a packer.PostProcessor implementation and makes it
 // exportable as part of a Golang RPC server.
 type PostProcessorServer struct {
+	context       context.Context
+	contextCancel func()
+
 	mux *muxBroker
 	p   packer.PostProcessor
 }
@@ -47,6 +51,20 @@ func (p *postProcessor) PostProcess(ctx context.Context, ui packer.Ui, a packer.
 	server.RegisterUi(ui)
 	go server.Serve()
 
+	done := make(chan interface{})
+	defer close(done)
+
+	go func() {
+		select {
+		case <-ctx.Done():
+			log.Printf("Cancelling post-processor after context cancellation %v", ctx.Err())
+			if err := p.client.Call("PostProcessor.Cancel", new(interface{}), new(interface{})); err != nil {
+				log.Printf("Error cancelling post-processor: %s", err)
+			}
+		case <-done:
+		}
+	}()
+
 	var response PostProcessorProcessResponse
 	if err := p.client.Call("PostProcessor.PostProcess", nextId, &response); err != nil {
 		return nil, false, err
@@ -73,15 +91,19 @@ func (p *PostProcessorServer) Configure(args *PostProcessorConfigureArgs, reply
 	return err
 }
 
-func (p *PostProcessorServer) PostProcess(ctx context.Context, streamId uint32, reply *PostProcessorProcessResponse) error {
+func (p *PostProcessorServer) PostProcess(streamId uint32, reply *PostProcessorProcessResponse) error {
 	client, err := newClientWithMux(p.mux, streamId)
 	if err != nil {
 		return NewBasicError(err)
 	}
 	defer client.Close()
 
+	if p.context == nil {
+		p.context, p.contextCancel = context.WithCancel(context.Background())
+	}
+
 	streamId = 0
-	artifactResult, keep, err := p.p.PostProcess(ctx, client.Ui(), client.Artifact())
+	artifactResult, keep, err := p.p.PostProcess(p.context, client.Ui(), client.Artifact())
 	if err == nil && artifactResult != nil {
 		streamId = p.mux.NextId()
 		server := newServerWithMux(p.mux, streamId)
@@ -97,3 +119,10 @@ func (p *PostProcessorServer) PostProcess(ctx context.Context, streamId uint32,
 
 	return nil
 }
+
+func (b *PostProcessorServer) Cancel(args *interface{}, reply *interface{}) error {
+	if b.contextCancel != nil {
+		b.contextCancel()
+	}
+	return nil
+}

packer/rpc/post_processor_test.go

@@ -17,6 +17,8 @@ type TestPostProcessor struct {
 	ppArtifact   packer.Artifact
 	ppArtifactId string
 	ppUi         packer.Ui
+
+	postProcessFn func(context.Context) error
 }
 
 func (pp *TestPostProcessor) Configure(v ...interface{}) error {
@@ -30,6 +32,9 @@ func (pp *TestPostProcessor) PostProcess(ctx context.Context, ui packer.Ui, a pa
 	pp.ppArtifact = a
 	pp.ppArtifactId = a.Id()
 	pp.ppUi = ui
+	if pp.postProcessFn != nil {
+		return testPostProcessorArtifact, false, pp.postProcessFn(ctx)
+	}
 	return testPostProcessorArtifact, false, nil
 }
 
@@ -84,6 +89,41 @@ func TestPostProcessorRPC(t *testing.T) {
 	}
 }
 
+func TestPostProcessorRPC_cancel(t *testing.T) {
+	topCtx, cancelTopCtx := context.WithCancel(context.Background())
+
+	p := new(TestPostProcessor)
+	p.postProcessFn = func(ctx context.Context) error {
+		cancelTopCtx()
+		<-ctx.Done()
+		return ctx.Err()
+	}
+
+	// Start the server
+	client, server := testClientServer(t)
+	defer client.Close()
+	defer server.Close()
+	if err := server.RegisterPostProcessor(p); err != nil {
+		panic(err)
+	}
+
+	ppClient := client.PostProcessor()
+
+	// Test Configure
+	config := 42
+	err := ppClient.Configure(config)
+
+	// Test PostProcess
+	a := &packer.MockArtifact{
+		IdValue: "ppTestId",
+	}
+	ui := new(testUi)
+	_, _, err = ppClient.PostProcess(topCtx, ui, a)
+	if err == nil {
+		t.Fatalf("should err")
+	}
+}
+
 func TestPostProcessor_Implements(t *testing.T) {
 	var raw interface{}
 	raw = new(postProcessor)

packer/rpc/provisioner.go

@@ -2,6 +2,7 @@ package rpc
 
 import (
 	"context"
+	"log"
 	"net/rpc"
 
 	"github.com/hashicorp/packer/packer"
@@ -17,6 +18,9 @@ type provisioner struct {
 // ProvisionerServer wraps a packer.Provisioner implementation and makes it
 // exportable as part of a Golang RPC server.
 type ProvisionerServer struct {
+	context       context.Context
+	contextCancel func()
+
 	p   packer.Provisioner
 	mux *muxBroker
 }
@@ -41,23 +45,46 @@ func (p *provisioner) Provision(ctx context.Context, ui packer.Ui, comm packer.C
 	server.RegisterUi(ui)
 	go server.Serve()
 
+	done := make(chan interface{})
+	defer close(done)
+
+	go func() {
+		select {
+		case <-ctx.Done():
+			log.Printf("Cancelling provisioner after context cancellation %v", ctx.Err())
+			if err := p.client.Call("Provisioner.Cancel", new(interface{}), new(interface{})); err != nil {
+				log.Printf("Error cancelling provisioner: %s", err)
+			}
+		case <-done:
+		}
+	}()
+
 	return p.client.Call("Provisioner.Provision", nextId, new(interface{}))
 }
 
-func (p *ProvisionerServer) Prepare(_ context.Context, args *ProvisionerPrepareArgs, reply *interface{}) error {
+func (p *ProvisionerServer) Prepare(args *ProvisionerPrepareArgs, reply *interface{}) error {
 	return p.p.Prepare(args.Configs...)
 }
 
-func (p *ProvisionerServer) Provision(ctx context.Context, streamId uint32, reply *interface{}) error {
+func (p *ProvisionerServer) Provision(streamId uint32, reply *interface{}) error {
 	client, err := newClientWithMux(p.mux, streamId)
 	if err != nil {
 		return NewBasicError(err)
 	}
 	defer client.Close()
 
-	if err := p.p.Provision(ctx, client.Ui(), client.Communicator()); err != nil {
+	if p.context == nil {
+		p.context, p.contextCancel = context.WithCancel(context.Background())
+	}
+
+	if err := p.p.Provision(p.context, client.Ui(), client.Communicator()); err != nil {
 		return NewBasicError(err)
 	}
 
 	return nil
 }
+
+func (p *ProvisionerServer) Cancel(args *interface{}, reply *interface{}) error {
+	p.contextCancel()
+	return nil
+}

packer/rpc/provisioner_test.go

@@ -9,8 +9,15 @@ import (
 )
 
 func TestProvisionerRPC(t *testing.T) {
+	topCtx, topCtxCancel := context.WithCancel(context.Background())
+
 	// Create the interface to test
 	p := new(packer.MockProvisioner)
+	p.ProvFunc = func(ctx context.Context) error {
+		topCtxCancel()
+		<-ctx.Done()
+		return ctx.Err()
+	}
 
 	// Start the server
 	client, server := testClientServer(t)
@@ -18,7 +25,6 @@ func TestProvisionerRPC(t *testing.T) {
 	defer server.Close()
 	server.RegisterProvisioner(p)
 	pClient := client.Provisioner()
-	ctx, cancel := context.WithCancel(context.Background())
 	// Test Prepare
 	config := 42
 	pClient.Prepare(config)
@@ -33,18 +39,13 @@ func TestProvisionerRPC(t *testing.T) {
 	// Test Provision
 	ui := &testUi{}
 	comm := &packer.MockCommunicator{}
-	if err := pClient.Provision(ctx, ui, comm); err != nil {
+	if err := pClient.Provision(topCtx, ui, comm); err == nil {
-		t.Fatalf("err: %v", err)
+		t.Fatalf("Provison should have err")
 	}
 	if !p.ProvCalled {
 		t.Fatal("should be called")
 	}
 
-	// Test Cancel
-	cancel()
-	if !p.CancelCalled {
-		t.Fatal("cancel should be called")
-	}
 }
 
 func TestProvisioner_Implements(t *testing.T) {

packer/rpc/server.go

@@ -32,12 +32,15 @@ type Server struct {
 }
 
 // NewServer returns a new Packer RPC server.
-func NewServer(conn io.ReadWriteCloser) *Server {
+func NewServer(conn io.ReadWriteCloser) (*Server, error) {
-	mux, _ := newMuxBrokerServer(conn)
+	mux, err := newMuxBrokerServer(conn)
+	if err != nil {
+		return nil, err
+	}
 	result := newServerWithMux(mux, 0)
 	result.closeMux = true
 	go mux.Run()
-	return result
+	return result, nil
 }
 
 func newServerWithMux(mux *muxBroker, streamId uint32) *Server {

provisioner/windows-restart/provisioner_test.go

@@ -342,40 +342,27 @@ func TestProvision_Cancel(t *testing.T) {
 	ui := testUi()
 	p := new(Provisioner)
 
-	var err error
-
 	comm := new(packer.MockCommunicator)
 	p.Prepare(config)
-	waitStart := make(chan bool)
+	done := make(chan error)
-	waitDone := make(chan bool)
+
+	topCtx, cancelTopCtx := context.WithCancel(context.Background())
 
 	// Block until cancel comes through
 	waitForCommunicator = func(ctx context.Context, p *Provisioner) error {
-		waitStart <- true
+		cancelTopCtx()
-		panic("this test is incorrect")
+		<-ctx.Done()
-		for {
+		return ctx.Err()
-			select {
-			case <-p.cancel:
-			}
-		}
 	}
-	ctx, cancel := context.WithCancel(context.Background())
 
 	// Create two go routines to provision and cancel in parallel
 	// Provision will block until cancel happens
 	go func() {
-		err = p.Provision(ctx, ui, comm)
+		done <- p.Provision(topCtx, ui, comm)
-		waitDone <- true
 	}()
 
-	go func() {
-		<-waitStart
-		cancel()
-	}()
-	<-waitDone
-
 	// Expect interrupt error
-	if err == nil {
+	if err := <-done; err == nil {
 		t.Fatal("should have error")
 	}
 }