skip configuration updates to the most recent one (#2690)

pkg/grpc/databroker/fast_forward.go

@@ -0,0 +1,107 @@
+package databroker
+
+import (
+	"context"
+	"time"
+
+	"github.com/pomerium/pomerium/internal/log"
+)
+
+// fastForwardHandler will skip
+type fastForwardHandler struct {
+	handler SyncerHandler
+	in      chan *ffCmd
+	exec    chan *ffCmd
+}
+
+type ffCmd struct {
+	clearRecords  bool
+	serverVersion uint64
+	records       []*Record
+}
+
+func newFastForwardHandler(ctx context.Context, handler SyncerHandler) SyncerHandler {
+	ff := &fastForwardHandler{
+		handler: handler,
+		in:      make(chan *ffCmd, 20),
+		exec:    make(chan *ffCmd),
+	}
+	go ff.runSelect(ctx)
+	go ff.runExec(ctx)
+
+	return ff
+}
+
+func (ff *fastForwardHandler) update(ctx context.Context, c *ffCmd) {
+	versions := make([]uint64, len(c.records))
+	for i, r := range c.records {
+		versions[i] = r.Version
+	}
+
+	now := time.Now()
+	ff.handler.UpdateRecords(ctx, c.serverVersion, c.records)
+	log.Info(ctx).
+		Dur("elapsed", time.Since(now)).
+		Uint64("server_version", c.serverVersion).
+		Uints64("versions", versions).
+		Msg("UpdateRecords")
+}
+
+func (ff *fastForwardHandler) runSelect(ctx context.Context) {
+	var update *ffCmd
+
+	for {
+		if update == nil {
+			select {
+			case <-ctx.Done():
+				return
+			case update = <-ff.in:
+			}
+		} else {
+			select {
+			case <-ctx.Done():
+				return
+			case update = <-ff.in:
+			case ff.exec <- update:
+				update = nil
+			}
+		}
+	}
+}
+
+func (ff *fastForwardHandler) runExec(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case update := <-ff.exec:
+			if update.clearRecords {
+				ff.handler.ClearRecords(ctx)
+				continue
+			}
+			ff.update(ctx, update)
+		}
+	}
+}
+
+func (ff *fastForwardHandler) GetDataBrokerServiceClient() DataBrokerServiceClient {
+	return ff.handler.GetDataBrokerServiceClient()
+}
+
+func (ff *fastForwardHandler) ClearRecords(ctx context.Context) {
+	select {
+	case <-ctx.Done():
+		log.Error(ctx).
+			Msg("ff_handler: ClearRecords: context canceled")
+	case ff.exec <- &ffCmd{clearRecords: true}:
+	}
+}
+
+func (ff *fastForwardHandler) UpdateRecords(ctx context.Context, serverVersion uint64, records []*Record) {
+	select {
+	case <-ctx.Done():
+		log.Error(ctx).
+			Msg("ff_handler: UpdateRecords: context canceled")
+	case ff.in <- &ffCmd{serverVersion: serverVersion, records: records}:
+	}
+}