traefik/healthcheck/healthcheck.go

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package healthcheck
import (
"context"
"fmt"
"net"
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"net/http"
"net/url"
"strconv"
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"sync"
"time"
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"github.com/containous/traefik/log"
"github.com/containous/traefik/safe"
"github.com/go-kit/kit/metrics"
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"github.com/vulcand/oxy/roundrobin"
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)
var singleton *HealthCheck
var once sync.Once
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// 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
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}
// Options are the public health check options.
type Options struct {
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Headers map[string]string
Hostname string
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Scheme string
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Path string
Port int
Transport http.RoundTripper
Interval time.Duration
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LB BalancerHandler
}
func (opt Options) String() string {
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return fmt.Sprintf("[Hostname: %s Headers: %v Path: %s Port: %d Interval: %s]", opt.Hostname, opt.Headers, opt.Path, opt.Port, opt.Interval)
}
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// BackendConfig HealthCheck configuration for a backend
type BackendConfig struct {
Options
name string
disabledURLs []*url.URL
requestTimeout time.Duration
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}
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func (b *BackendConfig) newRequest(serverURL *url.URL) (*http.Request, error) {
u := &url.URL{}
*u = *serverURL
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if len(b.Scheme) > 0 {
u.Scheme = b.Scheme
}
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if b.Port != 0 {
u.Host = net.JoinHostPort(u.Hostname(), strconv.Itoa(b.Port))
}
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u.Path += b.Path
return http.NewRequest(http.MethodGet, u.String(), nil)
}
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// 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)
}
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return req
}
// HealthCheck struct
type HealthCheck struct {
Backends map[string]*BackendConfig
metrics metricsRegistry
cancel context.CancelFunc
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}
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// SetBackendsConfiguration set backends configuration
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func (hc *HealthCheck) SetBackendsConfiguration(parentCtx context.Context, backends map[string]*BackendConfig) {
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hc.Backends = backends
if hc.cancel != nil {
hc.cancel()
}
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ctx, cancel := context.WithCancel(parentCtx)
hc.cancel = cancel
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for _, backend := range backends {
currentBackend := backend
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safe.Go(func() {
hc.execute(ctx, currentBackend)
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})
}
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}
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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.Debug("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)
}
}
}
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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)
}
}
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// 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
}
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func newHealthCheck(metrics metricsRegistry) *HealthCheck {
return &HealthCheck{
Backends: make(map[string]*BackendConfig),
metrics: metrics,
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}
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}
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// NewBackendConfig Instantiate a new BackendConfig
func NewBackendConfig(options Options, backendName string) *BackendConfig {
return &BackendConfig{
Options: options,
name: backendName,
requestTimeout: 5 * time.Second,
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}
}
// 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.
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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)
}
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req = backend.addHeadersAndHost(req)
client := http.Client{
Timeout: backend.requestTimeout,
Transport: backend.Options.Transport,
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}
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
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}