1 files changed, 52 insertions, 0 deletions
diff --git a/plugin/metrics/addr.go b/plugin/metrics/addr.go
new file mode 100644
index 000000000..fe8e5e5fe
--- /dev/null
+++ b/plugin/metrics/addr.go
@@ -0,0 +1,52 @@
+package metrics
+
+// addrs keeps track on which addrs we listen, so we only start one listener, is
+// prometheus is used in multiple Server Blocks.
+type addrs struct {
+	a map[string]value
+}
+
+type value struct {
+	state int
+	f     func() error
+}
+
+var uniqAddr addrs
+
+func newAddress() addrs {
+	return addrs{a: make(map[string]value)}
+}
+
+func (a addrs) setAddress(addr string, f func() error) {
+	if a.a[addr].state == done {
+		return
+	}
+	a.a[addr] = value{todo, f}
+}
+
+// setAddressTodo sets addr to 'todo' again.
+func (a addrs) setAddressTodo(addr string) {
+	v, ok := a.a[addr]
+	if !ok {
+		return
+	}
+	v.state = todo
+	a.a[addr] = v
+}
+
+// forEachTodo iterates for a and executes f for each element that is 'todo' and sets it to 'done'.
+func (a addrs) forEachTodo() error {
+	for k, v := range a.a {
+		if v.state == todo {
+			v.f()
+		}
+		v.state = done
+		a.a[k] = v
+	}
+	return nil
+}
+
+const (
+	todo = 1
+	done = 2
+)