Resolve $ to latest ID in XREAD

cmd_stream.go

@@ -924,11 +924,14 @@ parsing:
 			}
 
 			opts.streams, opts.ids = args[0:len(args)/2], args[len(args)/2:]
-			for _, id := range opts.ids {
+			for i, id := range opts.ids {
 				if _, err := parseStreamID(id); id != `$` && err != nil {
 					setDirty(c)
 					c.WriteError(msgInvalidStreamID)
 					return
+				} else if id == "$" {
+					db := m.DB(getCtx(c).selectedDB)
+					opts.ids[i] = db.streamKeys[opts.streams[i]].lastID()
 				}
 			}
 			args = nil

cmd_stream_test.go

@@ -5,6 +5,7 @@ import (
 	"math"
 	"regexp"
 	"strconv"
+	"sync"
 	"testing"
 	"time"
 
@@ -417,6 +418,34 @@ func TestStreamRead(t *testing.T) {
 				),
 			),
 		)
+
+		t.Run("blocking async", func(t *testing.T) {
+			// XREAD blocking test using latest ID
+			var wg sync.WaitGroup
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
+				mustDo(t, c,
+					"XREAD", "BLOCK", "0", "STREAMS", "planets", "$",
+					proto.Array(
+						proto.Array(proto.String("planets"),
+							proto.Array(
+								proto.Array(proto.String("5-1"), proto.Strings("name", "block", "idx", "6")),
+							),
+						),
+					),
+				)
+			}()
+
+			// Wait for the blocking XREAD to start and then run XADD
+			xaddClient, err := proto.Dial(s.Addr())
+			ok(t, err)
+			defer xaddClient.Close()
+
+			_, err = xaddClient.Do("XADD", "planets", "5-1", "name", "block", "idx", "6")
+			ok(t, err)
+			wg.Wait()
+		})
 	})
 
 	t.Run("error cases", func(t *testing.T) {

stream.go

@@ -9,6 +9,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -17,6 +18,7 @@ type streamKey struct {
 	entries         []StreamEntry
 	groups          map[string]*streamGroup
 	lastAllocatedID string
+	mu              sync.Mutex
 }
 
 // a StreamEntry is an entry in a stream. The ID is always of the form
@@ -52,6 +54,7 @@ func newStreamKey() *streamKey {
 	}
 }
 
+// generateID doesn't lock the mutex
 func (s *streamKey) generateID(now time.Time) string {
 	ts := uint64(now.UnixNano()) / 1_000_000
 
@@ -71,6 +74,7 @@ func (s *streamKey) generateID(now time.Time) string {
 	return next
 }
 
+// lastID doesn't lock the mutex
 func (s *streamKey) lastID() string {
 	if len(s.entries) == 0 {
 		return "0-0"
@@ -80,6 +84,9 @@ func (s *streamKey) lastID() string {
 }
 
 func (s *streamKey) copy() *streamKey {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	cpy := &streamKey{
 		entries: s.entries,
 	}
@@ -194,6 +201,9 @@ func reversedStreamEntries(o []StreamEntry) []StreamEntry {
 }
 
 func (s *streamKey) createGroup(group, id string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if _, ok := s.groups[group]; ok {
 		return errors.New("BUSYGROUP Consumer Group name already exists")
 	}
@@ -213,6 +223,9 @@ func (s *streamKey) createGroup(group, id string) error {
 // If id is empty or "*" the ID will be generated automatically.
 // `values` should have an even length.
 func (s *streamKey) add(entryID string, values []string, now time.Time) (string, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if entryID == "" || entryID == "*" {
 		entryID = s.generateID(now)
 	}
@@ -236,13 +249,19 @@ func (s *streamKey) add(entryID string, values []string, now time.Time) (string,
 }
 
 func (s *streamKey) trim(n int) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if len(s.entries) > n {
 		s.entries = s.entries[len(s.entries)-n:]
 	}
 }
 
 // all entries after "id"
 func (s *streamKey) after(id string) []StreamEntry {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	pos := sort.Search(len(s.entries), func(i int) bool {
 		return streamCmp(id, s.entries[i].ID) < 0
 	})
@@ -252,6 +271,9 @@ func (s *streamKey) after(id string) []StreamEntry {
 // get a stream entry by ID
 // Also returns the position in the entries slice, if found.
 func (s *streamKey) get(id string) (int, *StreamEntry) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	pos := sort.Search(len(s.entries), func(i int) bool {
 		return streamCmp(id, s.entries[i].ID) <= 0
 	})