package healthcheck import ( "context" "fmt" "net" "net/http" "net/url" "strconv" "sync" "time" "github.com/containous/traefik/log" "github.com/containous/traefik/safe" "github.com/go-kit/kit/metrics" "github.com/vulcand/oxy/roundrobin" ) var singleton *HealthCheck var once sync.Once // BalancerHandler includes functionality for load-balancing management. type BalancerHandler interface { ServeHTTP(w http.ResponseWriter, req *http.Request) Servers() []*url.URL RemoveServer(u *url.URL) error UpsertServer(u *url.URL, options ...roundrobin.ServerOption) error } // metricsRegistry is a local interface in the health check package, exposing only the required metrics // necessary for the health check package. This makes it easier for the tests. type metricsRegistry interface { BackendServerUpGauge() metrics.Gauge } // Options are the public health check options. type Options struct { Headers map[string]string Hostname string Scheme string Path string Port int Transport http.RoundTripper Interval time.Duration LB BalancerHandler } func (opt Options) String() string { return fmt.Sprintf("[Hostname: %s Headers: %v Path: %s Port: %d Interval: %s]", opt.Hostname, opt.Headers, opt.Path, opt.Port, opt.Interval) } // BackendConfig HealthCheck configuration for a backend type BackendConfig struct { Options name string disabledURLs []*url.URL requestTimeout time.Duration } func (b *BackendConfig) newRequest(serverURL *url.URL) (*http.Request, error) { u := &url.URL{} *u = *serverURL if len(b.Scheme) > 0 { u.Scheme = b.Scheme } if b.Port != 0 { u.Host = net.JoinHostPort(u.Hostname(), strconv.Itoa(b.Port)) } u.Path += b.Path return http.NewRequest(http.MethodGet, u.String(), nil) } // this function adds additional http headers and hostname to http.request func (b *BackendConfig) addHeadersAndHost(req *http.Request) *http.Request { if b.Options.Hostname != "" { req.Host = b.Options.Hostname } for k, v := range b.Options.Headers { req.Header.Set(k, v) } return req } // HealthCheck struct type HealthCheck struct { Backends map[string]*BackendConfig metrics metricsRegistry cancel context.CancelFunc } // SetBackendsConfiguration set backends configuration func (hc *HealthCheck) SetBackendsConfiguration(parentCtx context.Context, backends map[string]*BackendConfig) { hc.Backends = backends if hc.cancel != nil { hc.cancel() } ctx, cancel := context.WithCancel(parentCtx) hc.cancel = cancel for _, backend := range backends { currentBackend := backend safe.Go(func() { hc.execute(ctx, currentBackend) }) } } func (hc *HealthCheck) execute(ctx context.Context, backend *BackendConfig) { log.Debugf("Initial health check for backend: %q", backend.name) hc.checkBackend(backend) ticker := time.NewTicker(backend.Interval) defer ticker.Stop() for { select { case <-ctx.Done(): log.Debugf("Stopping current health check goroutines of backend: %s", backend.name) return case <-ticker.C: log.Debugf("Refreshing health check for backend: %s", backend.name) hc.checkBackend(backend) } } } func (hc *HealthCheck) checkBackend(backend *BackendConfig) { enabledURLs := backend.LB.Servers() var newDisabledURLs []*url.URL for _, url := range backend.disabledURLs { serverUpMetricValue := float64(0) if err := checkHealth(url, backend); err == nil { log.Warnf("Health check up: Returning to server list. Backend: %q URL: %q", backend.name, url.String()) backend.LB.UpsertServer(url, roundrobin.Weight(1)) serverUpMetricValue = 1 } else { log.Warnf("Health check still failing. Backend: %q URL: %q Reason: %s", backend.name, url.String(), err) newDisabledURLs = append(newDisabledURLs, url) } labelValues := []string{"backend", backend.name, "url", url.String()} hc.metrics.BackendServerUpGauge().With(labelValues...).Set(serverUpMetricValue) } backend.disabledURLs = newDisabledURLs for _, url := range enabledURLs { serverUpMetricValue := float64(1) if err := checkHealth(url, backend); err != nil { log.Warnf("Health check failed: Remove from server list. Backend: %q URL: %q Reason: %s", backend.name, url.String(), err) backend.LB.RemoveServer(url) backend.disabledURLs = append(backend.disabledURLs, url) serverUpMetricValue = 0 } labelValues := []string{"backend", backend.name, "url", url.String()} hc.metrics.BackendServerUpGauge().With(labelValues...).Set(serverUpMetricValue) } } // GetHealthCheck returns the health check which is guaranteed to be a singleton. func GetHealthCheck(metrics metricsRegistry) *HealthCheck { once.Do(func() { singleton = newHealthCheck(metrics) }) return singleton } func newHealthCheck(metrics metricsRegistry) *HealthCheck { return &HealthCheck{ Backends: make(map[string]*BackendConfig), metrics: metrics, } } // NewBackendConfig Instantiate a new BackendConfig func NewBackendConfig(options Options, backendName string) *BackendConfig { return &BackendConfig{ Options: options, name: backendName, requestTimeout: 5 * time.Second, } } // checkHealth returns a nil error in case it was successful and otherwise // a non-nil error with a meaningful description why the health check failed. func checkHealth(serverURL *url.URL, backend *BackendConfig) error { req, err := backend.newRequest(serverURL) if err != nil { return fmt.Errorf("failed to create HTTP request: %s", err) } req = backend.addHeadersAndHost(req) client := http.Client{ Timeout: backend.requestTimeout, Transport: backend.Options.Transport, } resp, err := client.Do(req) if err != nil { return fmt.Errorf("HTTP request failed: %s", err) } defer resp.Body.Close() if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusBadRequest { return fmt.Errorf("received error status code: %v", resp.StatusCode) } return nil }