history: handle gracefulstop when history is active

When GracefulStop is called gRPC waits for current requests to finish
before closing. While this is generally the behavior we want, it is
not always same for the History.Listen endpoint. That endpoint is
usually open even if buildkit is not actively processing any builds,
because client may be waiting for new events.

The new logic is that if GracefulStop will happen, history will
close active listeners if there are no active builds. If there are
active builds then active listeners will be closed after all the
active builds have completed their finalizers.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

cmd/buildkitd/main.go

@@ -341,7 +341,7 @@ func main() {
 			return err
 		}
 
-		controller, err := newController(c, &cfg)
+		controller, err := newController(ctx, c, &cfg)
 		if err != nil {
 			return err
 		}
@@ -758,7 +758,7 @@ func serverCredentials(cfg config.TLSConfig) (*tls.Config, error) {
 	return tlsConf, nil
 }
 
-func newController(c *cli.Context, cfg *config.Config) (*control.Controller, error) {
+func newController(ctx context.Context, c *cli.Context, cfg *config.Config) (*control.Controller, error) {
 	sessionManager, err := session.NewManager()
 	if err != nil {
 		return nil, err
@@ -851,6 +851,7 @@ func newController(c *cli.Context, cfg *config.Config) (*control.Controller, err
 		ContentStore:              w.ContentStore(),
 		HistoryConfig:             cfg.History,
 		GarbageCollect:            w.GarbageCollect,
+		GracefulStop:              ctx.Done(),
 	})
 }
 

control/control.go

@@ -71,6 +71,7 @@ type Opt struct {
 	ContentStore              *containerdsnapshot.Store
 	HistoryConfig             *config.HistoryConfig
 	GarbageCollect            func(context.Context) error
+	GracefulStop              <-chan struct{}
 }
 
 type Controller struct { // TODO: ControlService
@@ -95,6 +96,7 @@ func NewController(opt Opt) (*Controller, error) {
 		ContentStore:   opt.ContentStore,
 		CleanConfig:    opt.HistoryConfig,
 		GarbageCollect: opt.GarbageCollect,
+		GracefulStop:   opt.GracefulStop,
 	})
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to create history queue")

solver/llbsolver/history.go

@@ -47,6 +47,7 @@ type HistoryQueueOpt struct {
 	ContentStore   *containerdsnapshot.Store
 	CleanConfig    *config.HistoryConfig
 	GarbageCollect func(context.Context) error
+	GracefulStop   <-chan struct{}
 }
 
 type HistoryQueue struct {
@@ -137,6 +138,16 @@ func NewHistoryQueue(opt HistoryQueueOpt) (*HistoryQueue, error) {
 		}
 	}()
 
+	go func() {
+		<-h.opt.GracefulStop
+		h.mu.Lock()
+		defer h.mu.Unlock()
+		// if active builds then close will happen in finalizer
+		if len(h.finalizers) == 0 && len(h.active) == 0 {
+			go h.ps.Close()
+		}
+	}()
+
 	return h, nil
 }
 
@@ -637,6 +648,14 @@ func (h *HistoryQueue) AcquireFinalizer(ref string) (<-chan struct{}, func()) {
 		<-f.done
 		h.mu.Lock()
 		delete(h.finalizers, ref)
+		// if gracefulstop then release listeners after finalize
+		if len(h.finalizers) == 0 {
+			select {
+			case <-h.opt.GracefulStop:
+				go h.ps.Close()
+			default:
+			}
+		}
 		h.mu.Unlock()
 	}()
 	return trigger, sync.OnceFunc(func() {
@@ -1032,6 +1051,18 @@ func (p *pubsub[T]) Send(v T) {
 	p.mu.Unlock()
 }
 
+func (p *pubsub[T]) Close() {
+	p.mu.Lock()
+	channels := make([]*channel[T], 0, len(p.m))
+	for c := range p.m {
+		channels = append(channels, c)
+	}
+	p.mu.Unlock()
+	for _, c := range channels {
+		c.close()
+	}
+}
+
 type channel[T any] struct {
 	ps        *pubsub[T]
 	ch        chan T