util: Add an easy ACK sync primitive

util/sync.go

@@ -21,6 +21,28 @@ import (
 	"sync"
 )
 
+// EasyAck is a wrapper to build ack functionality into a simple interface.
+type EasyAck struct {
+	done chan struct{}
+}
+
+// NewEasyAck builds the object. This must be called before use.
+func NewEasyAck() *EasyAck {
+	return &EasyAck{
+		done: make(chan struct{}),
+	}
+}
+
+// Ack sends the acknowledgment message. This can only be called once.
+func (obj *EasyAck) Ack() {
+	close(obj.done)
+}
+
+// Wait returns a channel that you can wait on for the ack message.
+func (obj *EasyAck) Wait() <-chan struct{} {
+	return obj.done
+}
+
 // EasyOnce is a wrapper for the sync.Once functionality which lets you define
 // and register the associated `run once` function at declaration time. It may
 // be copied at any time.

util/sync_test.go

@@ -0,0 +1,63 @@
+// Mgmt
+// Copyright (C) 2013-2018+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// +build !root
+
+package util
+
+import (
+	"testing"
+	"time"
+)
+
+func TestEasyAck1(t *testing.T) {
+	ea := NewEasyAck()
+	ea.Ack() // send the ack
+	select {
+	case <-ea.Wait(): // we got it!
+	case <-time.After(time.Duration(60) * time.Second):
+		t.Errorf("the Ack did not arrive in time")
+	}
+}
+
+func TestEasyAck2(t *testing.T) {
+	ea := NewEasyAck()
+	// never send an ack
+	select {
+	case <-ea.Wait(): // we got it!
+		t.Errorf("the Ack arrived unexpectedly")
+	default:
+	}
+}
+
+func TestEasyAck3(t *testing.T) {
+	ea := NewEasyAck()
+	ea.Ack() // send the ack
+	select {
+	case <-ea.Wait(): // we got it!
+	case <-time.After(time.Duration(60) * time.Second):
+		t.Errorf("the Ack did not arrive in time")
+	}
+
+	ea = NewEasyAck() // build a new one
+	ea.Ack()          // send the ack
+	select {
+	case <-ea.Wait(): // we got it!
+	case <-time.After(time.Duration(60) * time.Second):
+		t.Errorf("the second Ack did not arrive in time")
+	}
+}