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fix: avoid missed wakeups in rpc stream subscribe #1184

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fix: avoid missed wakeups in rpc stream subscribe #1184

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14 changes: 11 additions & 3 deletions rpc/stream/cond.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,11 +15,19 @@ func NewCond() *Cond {
return &Cond{ch: make(chan struct{})}
}

func (c *Cond) Channel() <-chan struct{} {
c.mu.Lock()
defer c.mu.Unlock()

return c.ch
}

// Wait returns true if the condition is signaled, false if the context is canceled
func (c *Cond) Wait(ctx context.Context) bool {
c.mu.Lock()
ch := c.ch
c.mu.Unlock()
return c.WaitChannel(ctx, c.Channel())
}

func (c *Cond) WaitChannel(ctx context.Context, ch <-chan struct{}) bool {

select {
case <-ch:
Expand Down
10 changes: 8 additions & 2 deletions rpc/stream/stream.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,8 +71,13 @@ func (s *Stream[V]) Add(vs ...V) int {
func (s *Stream[V]) Subscribe(ctx context.Context, callback func([]V, int) error) error {
var (
items []V
offset = -1
offset int
)

s.mutex.RLock()
offset = s.lastID()
s.mutex.RUnlock()

for {
items, offset = s.ReadBlocking(ctx, offset)
if len(items) == 0 {
Expand Down Expand Up @@ -130,8 +135,9 @@ func (s *Stream[V]) ReadBlocking(ctx context.Context, offset int) ([]V, int) {
return items, offset
}

ch := s.cond.Channel()
s.mutex.RUnlock()
r := s.cond.Wait(ctx)
r := s.cond.WaitChannel(ctx, ch)
s.mutex.RLock()

if !r {
Expand Down