Don't stop when there is work to be done

federationsender/queue/destinationqueue.go

@@ -46,7 +46,6 @@ type destinationQueue struct {
 	running          atomic.Bool                             // is the queue worker running?
 	backingOff       atomic.Bool                             // true if we're backing off
 	statistics       *types.ServerStatistics                 // statistics about this remote server
-	incomingPDUs     chan struct{}                           // signal that there are PDUs waiting
 	incomingInvites  chan *gomatrixserverlib.InviteV2Request // invites to send
 	incomingEDUs     chan *gomatrixserverlib.EDU             // EDUs to send
 	transactionID    gomatrixserverlib.TransactionID         // last transaction ID
@@ -54,6 +53,7 @@ type destinationQueue struct {
 	pendingPDUs      atomic.Int32                            // how many PDUs are waiting to be sent
 	pendingEDUs      []*gomatrixserverlib.EDU                // owned by backgroundSend
 	pendingInvites   []*gomatrixserverlib.InviteV2Request    // owned by backgroundSend
+	wakeServerCh     chan bool                               // interrupts idle wait
 	retryServerCh    chan bool                               // interrupts backoff
 }
 
@@ -120,7 +120,7 @@ func (oq *destinationQueue) sendEvent(nid int64) {
 	// Signal that we've sent a new PDU. This will cause the queue to
 	// wake up if it's asleep.
 	oq.pendingPDUs.Add(1)
-	oq.incomingPDUs <- struct{}{}
+	oq.wakeServerCh <- true
 }
 
 // sendEDU adds the EDU event to the pending queue for the destination.
@@ -168,10 +168,11 @@ func (oq *destinationQueue) backgroundSend() {
 		// e.g. in response to EDUs.
 		transactionID := gomatrixserverlib.TransactionID("")
 
-		// Wait either for incoming events, or until we hit an
-		// idle timeout.
+		// If we have nothing to do then wait either for incoming events, or
+		// until we hit an idle timeout.
+		if oq.pendingPDUs.Load() == 0 {
 			select {
-		case <-oq.incomingPDUs:
+			case <-oq.wakeServerCh:
 				// We were woken up because there are new PDUs waiting in the
 				// database.
 			case edu := <-oq.incomingEDUs:
@@ -209,6 +210,7 @@ func (oq *destinationQueue) backgroundSend() {
 				// send.
 				return
 			}
+		}
 
 		// If we are backing off this server then wait for the
 		// backoff duration to complete first, or until explicitly

federationsender/queue/queue.go

@@ -88,9 +88,9 @@ func (oqs *OutgoingQueues) getQueue(destination gomatrixserverlib.ServerName) *d
 			destination:     destination,
 			client:          oqs.client,
 			statistics:      oqs.statistics.ForServer(destination),
-			incomingPDUs:    make(chan struct{}, 128),
 			incomingEDUs:    make(chan *gomatrixserverlib.EDU, 128),
 			incomingInvites: make(chan *gomatrixserverlib.InviteV2Request, 128),
+			wakeServerCh:    make(chan bool, 128),
 			retryServerCh:   make(chan bool),
 			signing:         oqs.signing,
 		}