reverseproxy: Minor fixes and cleanup

Now use context cancellation to stop active health checker, which is
simpler than and just as effective as using a separate stop channel.

modules/caddyhttp/reverseproxy/healthchecks.go

@@ -78,7 +78,6 @@ type ActiveHealthChecks struct {
 	// body of a healthy backend.
 	ExpectBody string `json:"expect_body,omitempty"`
 
-	stopChan   chan struct{}
 	httpClient *http.Client
 	bodyRegexp *regexp.Regexp
 	logger     *zap.Logger
@@ -137,8 +136,7 @@ func (h *Handler) activeHealthChecker() {
 		select {
 		case <-ticker.C:
 			h.doActiveHealthCheckForAllHosts()
-		case <-h.HealthChecks.Active.stopChan:
-			// TODO: consider using a Context for cancellation instead
+		case <-h.ctx.Done():
 			ticker.Stop()
 			return
 		}
@@ -341,8 +339,8 @@ func (h *Handler) countFailure(upstream *Upstream) {
 	if err != nil {
 		h.HealthChecks.Passive.logger.Error("could not count failure",
 			zap.String("host", upstream.Dial),
-			zap.Error(err),
-		)
+			zap.Error(err))
+		return
 	}
 
 	// forget it later
@@ -357,8 +355,7 @@ func (h *Handler) countFailure(upstream *Upstream) {
 		if err != nil {
 			h.HealthChecks.Passive.logger.Error("could not forget failure",
 				zap.String("host", upstream.Dial),
-				zap.Error(err),
-			)
+				zap.Error(err))
 		}
 	}(upstream.Host, failDuration)
 }

modules/caddyhttp/reverseproxy/hosts.go

@@ -177,7 +177,7 @@ func (u *Upstream) fillDialInfo(r *http.Request) (DialInfo, error) {
 // of the state of a remote host. It implements the
 // Host interface.
 type upstreamHost struct {
-	numRequests int64 // must be first field to be 64-bit aligned on 32-bit systems (see https://golang.org/pkg/sync/atomic/#pkg-note-BUG)
+	numRequests int64 // must be 64-bit aligned on 32-bit systems (see https://golang.org/pkg/sync/atomic/#pkg-note-BUG)
 	fails       int64
 	unhealthy   int32
 }

modules/caddyhttp/reverseproxy/reverseproxy.go

@@ -112,6 +112,7 @@ type Handler struct {
 	Transport http.RoundTripper `json:"-"`
 	CB        CircuitBreaker    `json:"-"`
 
+	ctx    caddy.Context
 	logger *zap.Logger
 }
 
@@ -125,6 +126,7 @@ func (Handler) CaddyModule() caddy.ModuleInfo {
 
 // Provision ensures that h is set up properly before use.
 func (h *Handler) Provision(ctx caddy.Context) error {
+	h.ctx = ctx
 	h.logger = ctx.Logger(h)
 
 	// start by loading modules
@@ -235,9 +237,16 @@ func (h *Handler) Provision(ctx caddy.Context) error {
 		}
 	}
 
+	if h.HealthChecks != nil {
+		// set defaults on passive health checks, if necessary
+		if h.HealthChecks.Passive != nil {
+			if h.HealthChecks.Passive.FailDuration > 0 && h.HealthChecks.Passive.MaxFails == 0 {
+				h.HealthChecks.Passive.MaxFails = 1
+			}
+		}
+
 		// if active health checks are enabled, configure them and start a worker
-	if h.HealthChecks != nil &&
-		h.HealthChecks.Active != nil &&
+		if h.HealthChecks.Active != nil &&
 			(h.HealthChecks.Active.Path != "" || h.HealthChecks.Active.Port != 0) {
 			h.HealthChecks.Active.logger = h.logger.Named("health_checker.active")
 
@@ -246,7 +255,6 @@ func (h *Handler) Provision(ctx caddy.Context) error {
 				timeout = 5 * time.Second
 			}
 
-		h.HealthChecks.Active.stopChan = make(chan struct{})
 			h.HealthChecks.Active.httpClient = &http.Client{
 				Timeout:   timeout,
 				Transport: h.Transport,
@@ -266,6 +274,7 @@ func (h *Handler) Provision(ctx caddy.Context) error {
 
 			go h.activeHealthChecker()
 		}
+	}
 
 	// set up any response routes
 	for i, rh := range h.HandleResponse {
@@ -280,14 +289,6 @@ func (h *Handler) Provision(ctx caddy.Context) error {
 
 // Cleanup cleans up the resources made by h during provisioning.
 func (h *Handler) Cleanup() error {
-	// stop the active health checker
-	if h.HealthChecks != nil &&
-		h.HealthChecks.Active != nil &&
-		h.HealthChecks.Active.stopChan != nil {
-		// TODO: consider using context cancellation, could be much simpler
-		close(h.HealthChecks.Active.stopChan)
-	}
-
 	// TODO: Close keepalive connections on reload? https://github.com/caddyserver/caddy/pull/2507/files#diff-70219fd88fe3f36834f474ce6537ed26R762
 
 	// remove hosts from our config from the pool
@@ -351,7 +352,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyht
 			if proxyErr == nil {
 				proxyErr = fmt.Errorf("no upstreams available")
 			}
-			if !h.LoadBalancing.tryAgain(start, proxyErr, r) {
+			if !h.LoadBalancing.tryAgain(h.ctx, start, proxyErr, r) {
 				break
 			}
 			continue
@@ -410,7 +411,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyht
 		h.countFailure(upstream)
 
 		// if we've tried long enough, break
-		if !h.LoadBalancing.tryAgain(start, proxyErr, r) {
+		if !h.LoadBalancing.tryAgain(h.ctx, start, proxyErr, r) {
 			break
 		}
 	}
@@ -661,7 +662,7 @@ func (h *Handler) reverseProxy(rw http.ResponseWriter, req *http.Request, di Dia
 // long enough before the next retry (i.e. no more sleeping is
 // needed). If false is returned, the handler should stop trying to
 // proxy the request.
-func (lb LoadBalancing) tryAgain(start time.Time, proxyErr error, req *http.Request) bool {
+func (lb LoadBalancing) tryAgain(ctx caddy.Context, start time.Time, proxyErr error, req *http.Request) bool {
 	// if we've tried long enough, break
 	if time.Since(start) >= time.Duration(lb.TryDuration) {
 		return false
@@ -687,8 +688,12 @@ func (lb LoadBalancing) tryAgain(start time.Time, proxyErr error, req *http.Requ
 	}
 
 	// otherwise, wait and try the next available host
-	time.Sleep(time.Duration(lb.TryInterval))
+	select {
+	case <-time.After(time.Duration(lb.TryInterval)):
 		return true
+	case <-ctx.Done():
+		return false
+	}
 }
 
 // directRequest modifies only req.URL so that it points to the upstream