package healthcheck import ( "context" "errors" "fmt" "net" "net/http" "net/url" "strconv" "time" gokitmetrics "github.com/go-kit/kit/metrics" "github.com/rs/zerolog/log" "github.com/traefik/traefik/v3/pkg/config/dynamic" "github.com/traefik/traefik/v3/pkg/config/runtime" "google.golang.org/grpc" "google.golang.org/grpc/codes" "google.golang.org/grpc/credentials/insecure" healthpb "google.golang.org/grpc/health/grpc_health_v1" "google.golang.org/grpc/status" ) const modeGRPC = "grpc" // StatusSetter should be implemented by a service that, when the status of a // registered target change, needs to be notified of that change. type StatusSetter interface { SetStatus(ctx context.Context, childName string, up bool) } // StatusUpdater should be implemented by a service that, when its status // changes (e.g. all if its children are down), needs to propagate upwards (to // their parent(s)) that change. type StatusUpdater interface { RegisterStatusUpdater(fn func(up bool)) error } type metricsHealthCheck interface { ServiceServerUpGauge() gokitmetrics.Gauge } type ServiceHealthChecker struct { balancer StatusSetter info *runtime.ServiceInfo config *dynamic.ServerHealthCheck interval time.Duration timeout time.Duration metrics metricsHealthCheck client *http.Client targets map[string]*url.URL } func NewServiceHealthChecker(ctx context.Context, metrics metricsHealthCheck, config *dynamic.ServerHealthCheck, service StatusSetter, info *runtime.ServiceInfo, transport http.RoundTripper, targets map[string]*url.URL) *ServiceHealthChecker { logger := log.Ctx(ctx) interval := time.Duration(config.Interval) if interval <= 0 { logger.Error().Msg("Health check interval smaller than zero") interval = time.Duration(dynamic.DefaultHealthCheckInterval) } timeout := time.Duration(config.Timeout) if timeout <= 0 { logger.Error().Msg("Health check timeout smaller than zero") timeout = time.Duration(dynamic.DefaultHealthCheckTimeout) } client := &http.Client{ Transport: transport, } if config.FollowRedirects != nil && !*config.FollowRedirects { client.CheckRedirect = func(req *http.Request, via []*http.Request) error { return http.ErrUseLastResponse } } return &ServiceHealthChecker{ balancer: service, info: info, config: config, interval: interval, timeout: timeout, targets: targets, client: client, metrics: metrics, } } func (shc *ServiceHealthChecker) Launch(ctx context.Context) { ticker := time.NewTicker(shc.interval) defer ticker.Stop() for { select { case <-ctx.Done(): return case <-ticker.C: for proxyName, target := range shc.targets { select { case <-ctx.Done(): return default: } up := true serverUpMetricValue := float64(1) if err := shc.executeHealthCheck(ctx, shc.config, target); err != nil { // The context is canceled when the dynamic configuration is refreshed. if errors.Is(err, context.Canceled) { return } log.Ctx(ctx).Warn(). Str("targetURL", target.String()). Err(err). Msg("Health check failed.") up = false serverUpMetricValue = float64(0) } shc.balancer.SetStatus(ctx, proxyName, up) statusStr := runtime.StatusDown if up { statusStr = runtime.StatusUp } shc.info.UpdateServerStatus(target.String(), statusStr) shc.metrics.ServiceServerUpGauge(). With("service", proxyName, "url", target.String()). Set(serverUpMetricValue) } } } } func (shc *ServiceHealthChecker) executeHealthCheck(ctx context.Context, config *dynamic.ServerHealthCheck, target *url.URL) error { ctx, cancel := context.WithDeadline(ctx, time.Now().Add(shc.timeout)) defer cancel() if config.Mode == modeGRPC { return shc.checkHealthGRPC(ctx, target) } return shc.checkHealthHTTP(ctx, target) } // checkHealthHTTP returns an error with a meaningful description if the health check failed. // Dedicated to HTTP servers. func (shc *ServiceHealthChecker) checkHealthHTTP(ctx context.Context, target *url.URL) error { req, err := shc.newRequest(ctx, target) if err != nil { return fmt.Errorf("create HTTP request: %w", err) } resp, err := shc.client.Do(req) if err != nil { return fmt.Errorf("HTTP request failed: %w", err) } defer resp.Body.Close() if shc.config.Status == 0 && (resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusBadRequest) { return fmt.Errorf("received error status code: %v", resp.StatusCode) } if shc.config.Status != 0 && shc.config.Status != resp.StatusCode { return fmt.Errorf("received error status code: %v expected status code: %v", resp.StatusCode, shc.config.Status) } return nil } func (shc *ServiceHealthChecker) newRequest(ctx context.Context, target *url.URL) (*http.Request, error) { u, err := target.Parse(shc.config.Path) if err != nil { return nil, err } if len(shc.config.Scheme) > 0 { u.Scheme = shc.config.Scheme } if shc.config.Port != 0 { u.Host = net.JoinHostPort(u.Hostname(), strconv.Itoa(shc.config.Port)) } req, err := http.NewRequestWithContext(ctx, shc.config.Method, u.String(), http.NoBody) if err != nil { return nil, fmt.Errorf("failed to create HTTP request: %w", err) } if shc.config.Hostname != "" { req.Host = shc.config.Hostname } for k, v := range shc.config.Headers { req.Header.Set(k, v) } return req, nil } // checkHealthGRPC returns an error with a meaningful description if the health check failed. // Dedicated to gRPC servers implementing gRPC Health Checking Protocol v1. func (shc *ServiceHealthChecker) checkHealthGRPC(ctx context.Context, serverURL *url.URL) error { u, err := serverURL.Parse(shc.config.Path) if err != nil { return fmt.Errorf("failed to parse server URL: %w", err) } port := u.Port() if shc.config.Port != 0 { port = strconv.Itoa(shc.config.Port) } serverAddr := net.JoinHostPort(u.Hostname(), port) var opts []grpc.DialOption switch shc.config.Scheme { case "http", "h2c", "": opts = append(opts, grpc.WithTransportCredentials(insecure.NewCredentials())) } conn, err := grpc.DialContext(ctx, serverAddr, opts...) if err != nil { if errors.Is(err, context.DeadlineExceeded) { return fmt.Errorf("fail to connect to %s within %s: %w", serverAddr, shc.config.Timeout, err) } return fmt.Errorf("fail to connect to %s: %w", serverAddr, err) } defer func() { _ = conn.Close() }() resp, err := healthpb.NewHealthClient(conn).Check(ctx, &healthpb.HealthCheckRequest{}) if err != nil { if stat, ok := status.FromError(err); ok { switch stat.Code() { case codes.Unimplemented: return fmt.Errorf("gRPC server does not implement the health protocol: %w", err) case codes.DeadlineExceeded: return fmt.Errorf("gRPC health check timeout: %w", err) case codes.Canceled: return context.Canceled } } return fmt.Errorf("gRPC health check failed: %w", err) } if resp.Status != healthpb.HealthCheckResponse_SERVING { return fmt.Errorf("received gRPC status code: %v", resp.Status) } return nil }