Use cancelable contexts for cloud provider plugin refreshes (#4226)

This commit uses a cancelable context to spawn goroutines that refresh
records from a cloud DNS provider. The Caddy shutdown routine uses the
returned cancel function to terminate existing goroutines when a USR1
reload signal is received.
Signed-off-by: Matt Kulka <mkulka@parchment.com>

plugin/azure/azure.go

@@ -87,11 +87,11 @@ func (h *Azure) Run(ctx context.Context) error {
 		for {
 			select {
 			case <-ctx.Done():
-				log.Infof("Breaking out of Azure update loop: %v", ctx.Err())
+				log.Debugf("Breaking out of Azure update loop for %v: %v", h.zoneNames, ctx.Err())
 				return
 			case <-time.After(1 * time.Minute):
 				if err := h.updateZones(ctx); err != nil && ctx.Err() == nil {
-					log.Errorf("Failed to update zones: %v", err)
+					log.Errorf("Failed to update zones %v: %v", h.zoneNames, err)
 				}
 			}
 		}

plugin/azure/setup.go

@@ -25,7 +25,7 @@ func setup(c *caddy.Controller) error {
 	if err != nil {
 		return plugin.Error("azure", err)
 	}
-	ctx := context.Background()
+	ctx, cancel := context.WithCancel(context.Background())
 
 	publicDNSClient := publicAzureDNS.NewRecordSetsClient(env.Values[auth.SubscriptionID])
 	if publicDNSClient.Authorizer, err = env.GetAuthorizer(); err != nil {
@@ -50,6 +50,7 @@ func setup(c *caddy.Controller) error {
 		h.Next = next
 		return h
 	})
+	c.OnShutdown(func() error { cancel(); return nil })
 	return nil
 }
 

plugin/clouddns/clouddns.go

@@ -85,11 +85,11 @@ func (h *CloudDNS) Run(ctx context.Context) error {
 		for {
 			select {
 			case <-ctx.Done():
-				log.Infof("Breaking out of CloudDNS update loop: %v", ctx.Err())
+				log.Debugf("Breaking out of CloudDNS update loop for %v: %v", h.zoneNames, ctx.Err())
 				return
 			case <-time.After(1 * time.Minute):
 				if err := h.updateZones(ctx); err != nil && ctx.Err() == nil /* Don't log error if ctx expired. */ {
-					log.Errorf("Failed to update zones: %v", err)
+					log.Errorf("Failed to update zones %v: %v", h.zoneNames, err)
 				}
 			}
 		}

plugin/clouddns/setup.go

@@ -78,7 +78,7 @@ func setup(c *caddy.Controller) error {
 			}
 		}
 
-		ctx := context.Background()
+		ctx, cancel := context.WithCancel(context.Background())
 		client, err := f(ctx, opt)
 		if err != nil {
 			return err
@@ -98,7 +98,7 @@ func setup(c *caddy.Controller) error {
 			h.Next = next
 			return h
 		})
-		c.OnShutdown(func() error { ctx.Done(); return nil })
+		c.OnShutdown(func() error { cancel(); return nil })
 	}
 
 	return nil

plugin/route53/route53.go

@@ -87,11 +87,11 @@ func (h *Route53) Run(ctx context.Context) error {
 		for {
 			select {
 			case <-ctx.Done():
-				log.Infof("Breaking out of Route53 update loop: %v", ctx.Err())
+				log.Debugf("Breaking out of Route53 update loop for %v: %v", h.zoneNames, ctx.Err())
 				return
 			case <-time.After(h.refresh):
 				if err := h.updateZones(ctx); err != nil && ctx.Err() == nil /* Don't log error if ctx expired. */ {
-					log.Errorf("Failed to update zones: %v", err)
+					log.Errorf("Failed to update zones %v: %v", h.zoneNames, err)
 				}
 			}
 		}

plugin/route53/setup.go

@@ -124,7 +124,7 @@ func setup(c *caddy.Controller) error {
 			Client: ec2metadata.New(session),
 		})
 		client := f(credentials.NewChainCredentials(providers))
-		ctx := context.Background()
+		ctx, cancel := context.WithCancel(context.Background())
 		h, err := New(ctx, client, keys, refresh)
 		if err != nil {
 			return plugin.Error("route53", c.Errf("failed to create route53 plugin: %v", err))
@@ -137,7 +137,7 @@ func setup(c *caddy.Controller) error {
 			h.Next = next
 			return h
 		})
-		c.OnShutdown(func() error { ctx.Done(); return nil })
+		c.OnShutdown(func() error { cancel(); return nil })
 	}
 	return nil
 }