optimize: improve breaker algorithm on recovery time (#4077)

core/breaker/bucket.go

@@ -0,0 +1,48 @@
+package breaker
+
+const (
+	success = iota
+	fail
+	drop
+)
+
+// bucket defines the bucket that holds sum and num of additions.
+type bucket struct {
+	Sum     int64
+	Success int64
+	Failure int64
+	Drop    int64
+}
+
+func (b *bucket) Add(v int64) {
+	switch v {
+	case fail:
+		b.fail()
+	case drop:
+		b.drop()
+	default:
+		b.succeed()
+	}
+}
+
+func (b *bucket) Reset() {
+	b.Sum = 0
+	b.Success = 0
+	b.Failure = 0
+	b.Drop = 0
+}
+
+func (b *bucket) drop() {
+	b.Sum++
+	b.Drop++
+}
+
+func (b *bucket) fail() {
+	b.Sum++
+	b.Failure++
+}
+
+func (b *bucket) succeed() {
+	b.Sum++
+	b.Success++
+}