make stop channel work properly for both maintainCerts and maintainOCSP

cmd/amppkg/main.go

@@ -98,7 +98,7 @@ func main() {
 		die(errors.Wrap(err, "building cert cache"))
 	}
 
-	if err = certCache.Init(nil); err != nil {
+	if err = certCache.Init(); err != nil {
 		if *flagDevelopment {
 			fmt.Println("WARNING:", err)
 		} else {

packager/certcache/certcache.go

@@ -88,6 +88,7 @@ type CertCache struct {
 	renewedCerts      []*x509.Certificate
 	ocspUpdateAfterMu sync.RWMutex
 	ocspUpdateAfter   time.Time
+	stop              chan struct{}
 	// TODO(twifkak): Implement a registry of Updateable instances which can be configured in the toml.
 	ocspFile     Updateable
 	ocspFilePath string
@@ -141,6 +142,7 @@ func New(certs []*x509.Certificate, certFetcher *certfetcher.CertFetcher, domain
 		//    you'd have one request, in the backend, and updating them all.
 		ocspFile:     &Chained{first: &InMemory{}, second: &LocalFile{path: ocspCache}},
 		ocspFilePath: ocspCache,
+		stop:         make(chan struct{}),
 		generateOCSPResponse: generateOCSPResponse,
 		client:       http.Client{Timeout: 60 * time.Second},
 		extractOCSPServer: func(cert *x509.Certificate) (string, error) {
@@ -165,7 +167,7 @@ func New(certs []*x509.Certificate, certFetcher *certfetcher.CertFetcher, domain
 	}
 }
 
-func (this *CertCache) Init(stop chan struct{}) error {
+func (this *CertCache) Init() error {
 	this.updateCertIfNecessary()
 
 	// Prime the OCSP disk and memory cache, so we can start serving immediately.
@@ -181,18 +183,31 @@ func (this *CertCache) Init(stop chan struct{}) error {
 	//    like the OCSP responder giving you junk, but also sufficient time
 	//    to raise an alert if something has gone really wrong.
 	// 7. The ability to serve old responses while fetching new responses.
-	go this.maintainOCSP(stop)
+	go this.maintainOCSP()
 
 	if this.certFetcher != nil {
 		// Update Certs in the background.
-		go this.maintainCerts(stop)
+		go this.maintainCerts()
 	}
 
 	this.isInitialized = true
 
 	return nil
 }
 
+// Stop stops the goroutines spawned in Init, which are automatically updating the certificate and the OCSP response.
+// It returns true if the call actually stops them, false if they have already been stopped.
+func (this *CertCache) Stop() bool {
+	select {
+	// this.stop will never be used for sending a value. Thus this case matches only when it has already been closed.
+	case <-this.stop:
+		return false
+	default:
+		close(this.stop)
+		return true
+	}
+}
+
 // Gets the latest cert.
 // Returns the current cert if the cache has not been initialized or if the certFetcher is not set (good for testing)
 // If cert is invalid, it will attempt to renew.
@@ -422,7 +437,7 @@ func waitForSpecifiedTime(waitTimeInMinutes int, numRetries int) int {
 
 // Checks for OCSP updates every hour. Terminates only when stop receives
 // a message.
-func (this *CertCache) maintainOCSP(stop chan struct{}) {
+func (this *CertCache) maintainOCSP() {
 	// Only make one request per ocspCheckInterval, to minimize the impact
 	// on OCSP servers that are buckling under load, per sleevi requirement:
 	// 5. As with any system doing background requests on a remote server,
@@ -440,7 +455,7 @@ func (this *CertCache) maintainOCSP(stop chan struct{}) {
 			if err != nil {
 				log.Println("Warning: OCSP update failed. Cached response may expire:", err)
 			}
-		case <-stop:
+		case <-this.stop:
 			ticker.Stop()
 			return
 		}
@@ -635,7 +650,7 @@ func (this *CertCache) fetchOCSP(orig []byte, certs []*x509.Certificate, ocspUpd
 
 // Checks for cert updates every certCheckInterval hours. Terminates only when stop
 // receives a message.
-func (this *CertCache) maintainCerts(stop chan struct{}) {
+func (this *CertCache) maintainCerts() {
 	// Only make one request per certCheckInterval, to minimize the impact
 	// on servers that are buckling under load.
 	ticker := time.NewTicker(certCheckInterval)
@@ -644,7 +659,7 @@ func (this *CertCache) maintainCerts(stop chan struct{}) {
 		select {
 		case <-ticker.C:
 			this.updateCertIfNecessary()
-		case <-stop:
+		case <-this.stop:
 			ticker.Stop()
 			return
 		}

packager/certcache/certcache_test.go

@@ -68,7 +68,6 @@ type CertCacheSuite struct {
 	ocspServerWasCalled bool
 	ocspHandler         func(w http.ResponseWriter, req *http.Request)
 	tempDir             string
-	stop                chan struct{}
 	handler             *CertCache
 }
 
@@ -93,7 +92,7 @@ func (this *CertCacheSuite) New() (*CertCache, error) {
 			return defaultHttpExpiry(req, resp)
 		}
 	}
-	err := certCache.Init(this.stop)
+	err := certCache.Init()
 	return certCache, err
 }
 
@@ -121,8 +120,6 @@ func (this *CertCacheSuite) SetupTest() {
 	this.tempDir, err = ioutil.TempDir(os.TempDir(), "certcache_test")
 	this.Require().NoError(err, "setting up test harness")
 
-	this.stop = make(chan struct{})
-
 	this.handler, err = this.New()
 	this.Require().NoError(err, "instantiating CertCache")
 }
@@ -132,7 +129,7 @@ func (this *CertCacheSuite) TearDownTest() {
 	this.fakeOCSPExpiry = nil
 
 	// Reverse SetupTest.
-	this.stop <- struct{}{}
+	this.handler.Stop()
 
 	err := os.RemoveAll(this.tempDir)
 	if err != nil {