p2p: simpler priority queue (backport #8929) (#8956)

internal/p2p/rqueue_test.go

@@ -0,0 +1,47 @@
+package p2p
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestSimpleQueue(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// set up a small queue with very small buffers so we can
+	// watch it shed load, then send a bunch of messages to the
+	// queue, most of which we'll watch it drop.
+	sq := newSimplePriorityQueue(ctx, 1, nil)
+	for i := 0; i < 100; i++ {
+		sq.enqueue() <- Envelope{From: "merlin"}
+	}
+
+	seen := 0
+
+RETRY:
+	for seen <= 2 {
+		select {
+		case e := <-sq.dequeue():
+			if e.From != "merlin" {
+				continue
+			}
+			seen++
+		case <-time.After(10 * time.Millisecond):
+			break RETRY
+		}
+	}
+	// if we don't see any messages, then it's just broken.
+	if seen == 0 {
+		t.Errorf("seen %d messages, should have seen more than one", seen)
+	}
+	// ensure that load shedding happens: there can be at most 3
+	// messages that we get out of this, one that was buffered
+	// plus 2 that were under the cap, everything else gets
+	// dropped.
+	if seen > 3 {
+		t.Errorf("saw %d messages, should have seen 5 or fewer", seen)
+	}
+
+}