Allow signals to be sent to gateway exec containers

Signed-off-by: Cory Bennett <cbennett@netflix.com>

client/build_test.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 
@@ -52,6 +53,7 @@ func TestClientGatewayIntegration(t *testing.T) {
 		testClientGatewaySlowCacheExecError,
 		testClientGatewayExecFileActionError,
 		testClientGatewayContainerExtraHosts,
+		testClientGatewayContainerSignal,
 		testWarnings,
 	), integration.WithMirroredImages(integration.OfficialImages("busybox:latest")))
 
@@ -1894,6 +1896,104 @@ func testClientGatewayContainerHostNetworking(t *testing.T, sb integration.Sandb
 	checkAllReleasable(t, c, sb, true)
 }
 
+// testClientGatewayContainerSignal is testing that we can send a signal
+func testClientGatewayContainerSignal(t *testing.T, sb integration.Sandbox) {
+	requiresLinux(t)
+	ctx := sb.Context()
+
+	c, err := New(ctx, sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	product := "buildkit_test"
+
+	b := func(ctx context.Context, c client.Client) (*client.Result, error) {
+		ctx, timeout := context.WithTimeout(ctx, 10*time.Second)
+		defer timeout()
+
+		st := llb.Image("busybox:latest")
+
+		def, err := st.Marshal(ctx)
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to marshal state")
+		}
+
+		r, err := c.Solve(ctx, client.SolveRequest{
+			Definition: def.ToPB(),
+		})
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to solve")
+		}
+
+		ctr1, err := c.NewContainer(ctx, client.NewContainerRequest{
+			Mounts: []client.Mount{{
+				Dest:      "/",
+				MountType: pb.MountType_BIND,
+				Ref:       r.Ref,
+			}},
+		})
+		require.NoError(t, err)
+		defer ctr1.Release(ctx)
+
+		pid1, err := ctr1.Start(ctx, client.StartRequest{
+			Args: []string{"sh", "-c", `trap 'kill $(jobs -p); exit 99' HUP; sleep 10 & wait`},
+		})
+		require.NoError(t, err)
+
+		// allow for the shell script to setup the trap before we signal it
+		time.Sleep(time.Second)
+
+		err = pid1.Signal(ctx, syscall.SIGHUP)
+		require.NoError(t, err)
+
+		err = pid1.Wait()
+		var exitError *gatewayapi.ExitError
+		require.ErrorAs(t, err, &exitError)
+		require.Equal(t, uint32(99), exitError.ExitCode)
+
+		// Now try again to signal an exec process
+
+		ctr2, err := c.NewContainer(ctx, client.NewContainerRequest{
+			Mounts: []client.Mount{{
+				Dest:      "/",
+				MountType: pb.MountType_BIND,
+				Ref:       r.Ref,
+			}},
+		})
+		require.NoError(t, err)
+		defer ctr2.Release(ctx)
+
+		pid1, err = ctr2.Start(ctx, client.StartRequest{
+			Args: []string{"sleep", "10"},
+		})
+		require.NoError(t, err)
+
+		pid2, err := ctr2.Start(ctx, client.StartRequest{
+			Args: []string{"sh", "-c", `trap 'kill $(jobs -p); exit 111' INT; sleep 10 & wait`},
+		})
+		require.NoError(t, err)
+
+		// allow for the shell script to setup the trap before we signal it
+		time.Sleep(time.Second)
+
+		err = pid2.Signal(ctx, syscall.SIGINT)
+		require.NoError(t, err)
+
+		err = pid2.Wait()
+		require.ErrorAs(t, err, &exitError)
+		require.Equal(t, uint32(111), exitError.ExitCode)
+
+		pid1.Signal(ctx, syscall.SIGKILL)
+		pid1.Wait()
+		return &client.Result{}, err
+	}
+
+	_, err = c.Build(ctx, SolveOpt{}, product, b, nil)
+	require.Error(t, err)
+
+	checkAllReleasable(t, c, sb, true)
+}
+
 type nopCloser struct {
 	io.Writer
 }

executor/containerdexecutor/executor.go

@@ -199,7 +199,7 @@ func (w *containerdExecutor) Run(ctx context.Context, id string, root executor.M
 		}
 	}()
 
-	err = w.runProcess(ctx, task, process.Resize, func() {
+	err = w.runProcess(ctx, task, process.Resize, process.Signal, func() {
 		startedOnce.Do(func() {
 			if started != nil {
 				close(started)
@@ -293,7 +293,7 @@ func (w *containerdExecutor) Exec(ctx context.Context, id string, process execut
 		return errors.WithStack(err)
 	}
 
-	err = w.runProcess(ctx, taskProcess, process.Resize, nil)
+	err = w.runProcess(ctx, taskProcess, process.Resize, process.Signal, nil)
 	return err
 }
 
@@ -310,7 +310,7 @@ func fixProcessOutput(process *executor.ProcessInfo) {
 	}
 }
 
-func (w *containerdExecutor) runProcess(ctx context.Context, p containerd.Process, resize <-chan executor.WinSize, started func()) error {
+func (w *containerdExecutor) runProcess(ctx context.Context, p containerd.Process, resize <-chan executor.WinSize, signal <-chan syscall.Signal, started func()) error {
 	// Not using `ctx` here because the context passed only affects the statusCh which we
 	// don't want cancelled when ctx.Done is sent.  We want to process statusCh on cancel.
 	statusCh, err := p.Wait(context.Background())
@@ -335,22 +335,38 @@ func (w *containerdExecutor) runProcess(ctx context.Context, p containerd.Proces
 
 	p.CloseIO(ctx, containerd.WithStdinCloser)
 
-	// resize in separate go loop so it does not potentially block
-	// the container cancel/exit status loop below.
-	resizeCtx, resizeCancel := context.WithCancel(ctx)
-	defer resizeCancel()
+	// handle signals (and resize) in separate go loop so it does not
+	// potentially block the container cancel/exit status loop below.
+	eventCtx, eventCancel := context.WithCancel(ctx)
+	defer eventCancel()
 	go func() {
 		for {
 			select {
-			case <-resizeCtx.Done():
+			case <-eventCtx.Done():
 				return
 			case size, ok := <-resize:
 				if !ok {
 					return // chan closed
 				}
-				err = p.Resize(resizeCtx, size.Cols, size.Rows)
+				err = p.Resize(eventCtx, size.Cols, size.Rows)
 				if err != nil {
-					bklog.G(resizeCtx).Warnf("Failed to resize %s: %s", p.ID(), err)
+					bklog.G(eventCtx).Warnf("Failed to resize %s: %s", p.ID(), err)
+				}
+			}
+		}
+	}()
+	go func() {
+		for {
+			select {
+			case <-eventCtx.Done():
+				return
+			case sig, ok := <-signal:
+				if !ok {
+					return // chan closed
+				}
+				err = p.Kill(eventCtx, sig)
+				if err != nil {
+					bklog.G(eventCtx).Warnf("Failed to signal %s: %s", p.ID(), err)
 				}
 			}
 		}

executor/executor.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"io"
 	"net"
+	"syscall"
 
 	"github.com/moby/buildkit/snapshot"
 	"github.com/moby/buildkit/solver/pb"
@@ -45,6 +46,7 @@ type ProcessInfo struct {
 	Stdin          io.ReadCloser
 	Stdout, Stderr io.WriteCloser
 	Resize         <-chan WinSize
+	Signal         <-chan syscall.Signal
 }
 
 type Executor interface {

executor/runcexecutor/executor.go

@@ -315,14 +315,14 @@ func (w *runcExecutor) Run(ctx context.Context, id string, root executor.Mount,
 	}()
 
 	bklog.G(ctx).Debugf("> creating %s %v", id, meta.Args)
-	// this is a cheat, we have not actually started, but as close as we can get with runc for now
-	if started != nil {
+
+	err = w.run(runCtx, id, bundle, process, func() {
 		startedOnce.Do(func() {
-			close(started)
+			if started != nil {
+				close(started)
+			}
 		})
-	}
-
-	err = w.run(runCtx, id, bundle, process)
+	})
 	close(ended)
 	return exitError(ctx, err)
 }
@@ -414,7 +414,7 @@ func (w *runcExecutor) Exec(ctx context.Context, id string, process executor.Pro
 		spec.Process.Env = process.Meta.Env
 	}
 
-	err = w.exec(ctx, id, state.Bundle, spec.Process, process)
+	err = w.exec(ctx, id, state.Bundle, spec.Process, process, nil)
 	return exitError(ctx, err)
 }
 
@@ -444,3 +444,78 @@ func (s *forwardIO) Stdout() io.ReadCloser {
 func (s *forwardIO) Stderr() io.ReadCloser {
 	return nil
 }
+
+// startingProcess is to track the os process so we can send signals to it.
+type startingProcess struct {
+	Process *os.Process
+	found   chan struct{}
+}
+
+// Release will free resources with a startingProcess.
+func (p *startingProcess) Release() {
+	if p.Process != nil {
+		p.Process.Release()
+	}
+}
+
+// WaitForReady will wait until the Process has been populated or the
+// provided context was cancelled.  This should be called before using
+// the Process field.
+func (p *startingProcess) WaitForReady(ctx context.Context) error {
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-p.found:
+		return nil
+	}
+}
+
+// WaitForStart will record the pid reported by Runc via the channel.
+// We wait for up to 10s for the runc process to start.  If the started
+// callback is non-nil it will be called after receiving the pid.
+func (p *startingProcess) WaitForStart(ctx context.Context, startedCh chan int, started func()) error {
+	startedCtx, timeout := context.WithTimeout(ctx, 10*time.Second)
+	defer timeout()
+	var err error
+	select {
+	case <-startedCtx.Done():
+		return errors.New("runc started message never received")
+	case pid, ok := <-startedCh:
+		if !ok {
+			return errors.New("runc process failed to send pid")
+		}
+		if started != nil {
+			started()
+		}
+		p.Process, err = os.FindProcess(pid)
+		if err != nil {
+			return errors.Wrapf(err, "unable to find runc process for pid %d", pid)
+		}
+		close(p.found)
+	}
+	return nil
+}
+
+// handleSignals will wait until the runcProcess is ready then will
+// send each signal received on the channel to the process.
+func handleSignals(ctx context.Context, runcProcess *startingProcess, signals <-chan syscall.Signal) error {
+	if signals == nil {
+		return nil
+	}
+	err := runcProcess.WaitForReady(ctx)
+	if err != nil {
+		return err
+	}
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		case sig := <-signals:
+			err := runcProcess.Process.Signal(sig)
+			if err != nil {
+				bklog.G(ctx).Errorf("failed to signal %s to process: %s", sig, err)
+				return err
+			}
+		}
+	}
+}

executor/runcexecutor/executor_common.go

@@ -10,28 +10,63 @@ import (
 	"github.com/moby/buildkit/executor"
 	"github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
+	"golang.org/x/sync/errgroup"
 )
 
 var unsupportedConsoleError = errors.New("tty for runc is only supported on linux")
 
 func updateRuncFieldsForHostOS(runtime *runc.Runc) {}
 
-func (w *runcExecutor) run(ctx context.Context, id, bundle string, process executor.ProcessInfo) error {
+func (w *runcExecutor) run(ctx context.Context, id, bundle string, process executor.ProcessInfo, started func()) error {
 	if process.Meta.Tty {
 		return unsupportedConsoleError
 	}
-	_, err := w.runc.Run(ctx, id, bundle, &runc.CreateOpts{
-		IO:      &forwardIO{stdin: process.Stdin, stdout: process.Stdout, stderr: process.Stderr},
-		NoPivot: w.noPivot,
+	return w.commonCall(ctx, id, bundle, process, started, func(ctx context.Context, started chan<- int, io runc.IO) error {
+		_, err := w.runc.Run(ctx, id, bundle, &runc.CreateOpts{
+			NoPivot: w.noPivot,
+			Started: started,
+			IO:      io,
+		})
+		return err
 	})
-	return err
 }
 
-func (w *runcExecutor) exec(ctx context.Context, id, bundle string, specsProcess *specs.Process, process executor.ProcessInfo) error {
+func (w *runcExecutor) exec(ctx context.Context, id, bundle string, specsProcess *specs.Process, process executor.ProcessInfo, started func()) error {
 	if process.Meta.Tty {
 		return unsupportedConsoleError
 	}
-	return w.runc.Exec(ctx, id, *specsProcess, &runc.ExecOpts{
-		IO: &forwardIO{stdin: process.Stdin, stdout: process.Stdout, stderr: process.Stderr},
+	return w.commonCall(ctx, id, bundle, process, started, func(ctx context.Context, started chan<- int, io runc.IO) error {
+		return w.runc.Exec(ctx, id, *specsProcess, &runc.ExecOpts{
+			Started: started,
+			IO:      io,
+		})
 	})
 }
+
+type runcCall func(ctx context.Context, started chan<- int, io runc.IO) error
+
+// commonCall is the common run/exec logic used for non-linux runtimes. A tty
+// is only supported for linux, so this really just handles signal propagation
+// to the started runc process.
+func (w *runcExecutor) commonCall(ctx context.Context, id, bundle string, process executor.ProcessInfo, started func(), call runcCall) error {
+	runcProcess := &startingProcess{
+		found: make(chan struct{}),
+	}
+	defer runcProcess.Release()
+
+	var eg errgroup.Group
+	egCtx, cancel := context.WithCancel(ctx)
+	defer eg.Wait()
+	defer cancel()
+
+	startedCh := make(chan int, 1)
+	eg.Go(func() error {
+		return runcProcess.WaitForStart(egCtx, startedCh, started)
+	})
+
+	eg.Go(func() error {
+		return handleSignals(egCtx, runcProcess, process.Signal)
+	})
+
+	return call(ctx, startedCh, &forwardIO{stdin: process.Stdin, stdout: process.Stdout, stderr: process.Stderr})
+}