316 lines
8.5 KiB
Go
316 lines
8.5 KiB
Go
package healthcheck
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import (
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"context"
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"fmt"
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"net"
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"net/http"
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"net/url"
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"strconv"
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"sync"
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"time"
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"github.com/go-kit/kit/metrics"
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"github.com/traefik/traefik/v2/pkg/config/runtime"
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"github.com/traefik/traefik/v2/pkg/log"
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"github.com/traefik/traefik/v2/pkg/safe"
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"github.com/vulcand/oxy/roundrobin"
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)
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const (
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serverUp = "UP"
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serverDown = "DOWN"
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)
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var (
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singleton *HealthCheck
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once sync.Once
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)
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// Balancer is the set of operations required to manage the list of servers in a load-balancer.
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type Balancer interface {
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Servers() []*url.URL
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RemoveServer(u *url.URL) error
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UpsertServer(u *url.URL, options ...roundrobin.ServerOption) error
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}
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// BalancerHandler includes functionality for load-balancing management.
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type BalancerHandler interface {
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ServeHTTP(w http.ResponseWriter, req *http.Request)
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Balancer
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}
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// metricsRegistry is a local interface in the health check package,
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// exposing only the required metrics necessary for the health check package.
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// This makes it easier for the tests.
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type metricsRegistry interface {
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BackendServerUpGauge() metrics.Gauge
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}
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// Options are the public health check options.
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type Options struct {
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Headers map[string]string
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Hostname string
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Scheme string
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Path string
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Port int
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FollowRedirects bool
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Transport http.RoundTripper
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Interval time.Duration
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Timeout time.Duration
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LB Balancer
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}
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func (opt Options) String() string {
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return fmt.Sprintf("[Hostname: %s Headers: %v Path: %s Port: %d Interval: %s Timeout: %s FollowRedirects: %v]", opt.Hostname, opt.Headers, opt.Path, opt.Port, opt.Interval, opt.Timeout, opt.FollowRedirects)
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}
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type backendURL struct {
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url *url.URL
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weight int
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}
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// BackendConfig HealthCheck configuration for a backend.
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type BackendConfig struct {
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Options
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name string
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disabledURLs []backendURL
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}
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func (b *BackendConfig) newRequest(serverURL *url.URL) (*http.Request, error) {
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u, err := serverURL.Parse(b.Path)
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if err != nil {
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return nil, err
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}
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if len(b.Scheme) > 0 {
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u.Scheme = b.Scheme
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}
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if b.Port != 0 {
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u.Host = net.JoinHostPort(u.Hostname(), strconv.Itoa(b.Port))
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}
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return http.NewRequest(http.MethodGet, u.String(), http.NoBody)
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}
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// this function adds additional http headers and hostname to http.request.
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func (b *BackendConfig) addHeadersAndHost(req *http.Request) *http.Request {
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if b.Options.Hostname != "" {
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req.Host = b.Options.Hostname
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}
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for k, v := range b.Options.Headers {
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req.Header.Set(k, v)
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}
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return req
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}
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// HealthCheck struct.
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type HealthCheck struct {
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Backends map[string]*BackendConfig
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metrics metricsRegistry
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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
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if hc.cancel != nil {
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hc.cancel()
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}
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ctx, cancel := context.WithCancel(parentCtx)
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hc.cancel = cancel
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for _, backend := range backends {
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currentBackend := backend
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safe.Go(func() {
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hc.execute(ctx, currentBackend)
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})
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}
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}
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func (hc *HealthCheck) execute(ctx context.Context, backend *BackendConfig) {
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logger := log.FromContext(ctx)
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logger.Debugf("Initial health check for backend: %q", backend.name)
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hc.checkBackend(ctx, backend)
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ticker := time.NewTicker(backend.Interval)
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defer ticker.Stop()
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for {
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select {
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case <-ctx.Done():
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logger.Debugf("Stopping current health check goroutines of backend: %s", backend.name)
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return
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case <-ticker.C:
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logger.Debugf("Refreshing health check for backend: %s", backend.name)
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hc.checkBackend(ctx, backend)
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}
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}
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}
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func (hc *HealthCheck) checkBackend(ctx context.Context, backend *BackendConfig) {
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logger := log.FromContext(ctx)
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enabledURLs := backend.LB.Servers()
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var newDisabledURLs []backendURL
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for _, disabledURL := range backend.disabledURLs {
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if err := checkHealth(disabledURL.url, backend); err == nil {
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logger.Warnf("Health check up: Returning to server list. Backend: %q URL: %q Weight: %d",
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backend.name, disabledURL.url.String(), disabledURL.weight)
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if err = backend.LB.UpsertServer(disabledURL.url, roundrobin.Weight(disabledURL.weight)); err != nil {
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logger.Error(err)
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}
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} else {
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logger.Warnf("Health check still failing. Backend: %q URL: %q Reason: %s", backend.name, disabledURL.url.String(), err)
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newDisabledURLs = append(newDisabledURLs, disabledURL)
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}
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}
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backend.disabledURLs = newDisabledURLs
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for _, enableURL := range enabledURLs {
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if err := checkHealth(enableURL, backend); err != nil {
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weight := 1
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rr, ok := backend.LB.(*roundrobin.RoundRobin)
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if ok {
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var gotWeight bool
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weight, gotWeight = rr.ServerWeight(enableURL)
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if !gotWeight {
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weight = 1
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}
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}
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logger.Warnf("Health check failed, removing from server list. Backend: %q URL: %q Weight: %d Reason: %s", backend.name, enableURL.String(), weight, err)
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if err := backend.LB.RemoveServer(enableURL); err != nil {
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logger.Error(err)
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}
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backend.disabledURLs = append(backend.disabledURLs, backendURL{enableURL, weight})
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}
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}
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}
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// GetHealthCheck returns the health check which is guaranteed to be a singleton.
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func GetHealthCheck() *HealthCheck {
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once.Do(func() {
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singleton = newHealthCheck()
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})
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return singleton
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}
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func newHealthCheck() *HealthCheck {
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return &HealthCheck{
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Backends: make(map[string]*BackendConfig),
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}
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}
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// NewBackendConfig Instantiate a new BackendConfig.
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func NewBackendConfig(options Options, backendName string) *BackendConfig {
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return &BackendConfig{
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Options: options,
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name: backendName,
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}
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}
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// checkHealth returns a nil error in case it was successful and otherwise
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// 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 {
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req, err := backend.newRequest(serverURL)
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if err != nil {
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return fmt.Errorf("failed to create HTTP request: %w", err)
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}
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req = backend.addHeadersAndHost(req)
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client := http.Client{
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Timeout: backend.Options.Timeout,
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Transport: backend.Options.Transport,
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}
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if !backend.FollowRedirects {
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client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
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return http.ErrUseLastResponse
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}
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}
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resp, err := client.Do(req)
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if err != nil {
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return fmt.Errorf("HTTP request failed: %w", err)
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}
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defer resp.Body.Close()
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if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusBadRequest {
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return fmt.Errorf("received error status code: %v", resp.StatusCode)
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}
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return nil
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}
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// NewLBStatusUpdater returns a new LbStatusUpdater.
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func NewLBStatusUpdater(bh BalancerHandler, info *runtime.ServiceInfo) *LbStatusUpdater {
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return &LbStatusUpdater{
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BalancerHandler: bh,
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serviceInfo: info,
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}
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}
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// LbStatusUpdater wraps a BalancerHandler and a ServiceInfo,
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// so it can keep track of the status of a server in the ServiceInfo.
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type LbStatusUpdater struct {
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BalancerHandler
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serviceInfo *runtime.ServiceInfo // can be nil
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}
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// RemoveServer removes the given server from the BalancerHandler,
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// and updates the status of the server to "DOWN".
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func (lb *LbStatusUpdater) RemoveServer(u *url.URL) error {
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err := lb.BalancerHandler.RemoveServer(u)
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if err == nil && lb.serviceInfo != nil {
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lb.serviceInfo.UpdateServerStatus(u.String(), serverDown)
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}
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return err
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}
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// UpsertServer adds the given server to the BalancerHandler,
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// and updates the status of the server to "UP".
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func (lb *LbStatusUpdater) UpsertServer(u *url.URL, options ...roundrobin.ServerOption) error {
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err := lb.BalancerHandler.UpsertServer(u, options...)
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if err == nil && lb.serviceInfo != nil {
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lb.serviceInfo.UpdateServerStatus(u.String(), serverUp)
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}
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return err
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}
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// Balancers is a list of Balancers(s) that implements the Balancer interface.
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type Balancers []Balancer
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// Servers returns the servers url from all the BalancerHandler.
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func (b Balancers) Servers() []*url.URL {
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var servers []*url.URL
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for _, lb := range b {
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servers = append(servers, lb.Servers()...)
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}
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return servers
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}
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// RemoveServer removes the given server from all the BalancerHandler,
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// and updates the status of the server to "DOWN".
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func (b Balancers) RemoveServer(u *url.URL) error {
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for _, lb := range b {
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if err := lb.RemoveServer(u); err != nil {
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return err
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}
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}
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return nil
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}
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// UpsertServer adds the given server to all the BalancerHandler,
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// and updates the status of the server to "UP".
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func (b Balancers) UpsertServer(u *url.URL, options ...roundrobin.ServerOption) error {
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for _, lb := range b {
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if err := lb.UpsertServer(u, options...); err != nil {
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return err
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}
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}
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return nil
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}
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