snapshot of https://github.com/livekit/livekit.git @ 08c5433449c106943231037d0b892895f6e92d3b (2026-09-15)

pkg/rtc/migrationdatacache.go

@@ -0,0 +1,69 @@
+package rtc
+
+import (
+	"time"
+
+	"github.com/livekit/protocol/livekit"
+)
+
+type MigrationDataCacheState int
+
+const (
+	MigrationDataCacheStateWaiting MigrationDataCacheState = iota
+	MigrationDataCacheStateTimeout
+	MigrationDataCacheStateDone
+)
+
+const (
+	migrationDataCacheMaxSize = 4 << 20 // 4 MiB
+)
+
+type MigrationDataCache struct {
+	lastSeq   uint32
+	pkts      []*livekit.DataPacket
+	size      int
+	state     MigrationDataCacheState
+	expiredAt time.Time
+}
+
+func NewMigrationDataCache(lastSeq uint32, expiredAt time.Time) *MigrationDataCache {
+	return &MigrationDataCache{
+		lastSeq:   lastSeq,
+		expiredAt: expiredAt,
+	}
+}
+
+// Add adds a message to the cache if there is a gap between the last sequence number and cached messages then return the cache State:
+//   - MigrationDataCacheStateWaiting: waiting for the next packet (lastSeq + 1) of last sequence from old node
+//   - MigrationDataCacheStateTimeout: the next packet is not received before the expiredAt or the cache is full, participant
+//     will continue to process the reliable messages, subscribers will see the gap after the publisher migration
+//   - MigrationDataCacheStateDone: the next packet is received, participant can continue to process the reliable messages
+func (c *MigrationDataCache) Add(pkt *livekit.DataPacket, size int) MigrationDataCacheState {
+	if c.state == MigrationDataCacheStateDone || c.state == MigrationDataCacheStateTimeout {
+		return c.state
+	}
+
+	if pkt.Sequence <= c.lastSeq {
+		return c.state
+	}
+
+	if pkt.Sequence == c.lastSeq+1 {
+		c.state = MigrationDataCacheStateDone
+		return c.state
+	}
+
+	c.pkts = append(c.pkts, pkt)
+	c.size += size
+	if c.size >= migrationDataCacheMaxSize || time.Now().After(c.expiredAt) {
+		c.state = MigrationDataCacheStateTimeout
+	}
+	return c.state
+}
+
+func (c *MigrationDataCache) Get() []*livekit.DataPacket {
+	return c.pkts
+}
+
+func (c *MigrationDataCache) Size() int {
+	return c.size
+}