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discovery: sanitize Consul service discovery
This commits simplifies the SD's structure and ensures that all channel sends are checked against a canceled context.
This commit is contained in:
Fabian Reinartz
parent
5837e6a97f
commit
e805e68c01
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@ -17,7 +17,6 @@ import (
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"fmt"
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"strconv"
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"strings"
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"sync"
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"time"
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consul "github.com/hashicorp/consul/api"
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@ -57,20 +56,7 @@ type Discovery struct {
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clientConf *consul.Config
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clientDatacenter string
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tagSeparator string
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scrapedServices map[string]struct{}
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mu sync.RWMutex
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services map[string]*consulService
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}
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// consulService contains data belonging to the same service.
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type consulService struct {
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name string
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tgroup config.TargetGroup
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lastIndex uint64
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removed bool
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running bool
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done chan struct{}
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scrapedServices map[string]struct{} // Set of services which will be discovered.
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}
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// NewDiscovery returns a new Discovery for the given config.
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@ -94,7 +80,6 @@ func NewDiscovery(conf *config.ConsulSDConfig) (*Discovery, error) {
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clientConf: clientConf,
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tagSeparator: conf.TagSeparator,
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scrapedServices: map[string]struct{}{},
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services: map[string]*consulService{},
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}
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// If the datacenter isn't set in the clientConf, let's get it from the local Consul agent
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// (Consul default is to use local node's datacenter if one isn't given for a query).
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@ -116,46 +101,10 @@ func NewDiscovery(conf *config.ConsulSDConfig) (*Discovery, error) {
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// Run implements the TargetProvider interface.
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func (cd *Discovery) Run(ctx context.Context, ch chan<- []*config.TargetGroup) {
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defer close(ch)
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defer cd.stop()
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update := make(chan *consulService, 10)
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go cd.watchServices(update, ctx.Done())
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// Watched services and their cancelation functions.
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services := map[string]func(){}
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for {
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select {
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case <-ctx.Done():
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return
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case srv := <-update:
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if srv.removed {
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close(srv.done)
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// Send clearing update.
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ch <- []*config.TargetGroup{{Source: srv.name}}
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break
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}
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// Launch watcher for the service.
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if !srv.running {
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go cd.watchService(srv, ch)
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srv.running = true
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}
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}
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}
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}
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func (cd *Discovery) stop() {
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// The lock prevents Run from terminating while the watchers attempt
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// to send on their channels.
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cd.mu.Lock()
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defer cd.mu.Unlock()
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for _, srv := range cd.services {
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close(srv.done)
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}
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}
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// watchServices retrieves updates from Consul's services endpoint and sends
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// potential updates to the update channel.
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func (cd *Discovery) watchServices(update chan<- *consulService, done <-chan struct{}) {
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var lastIndex uint64
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for {
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catalog := cd.client.Catalog()
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@ -163,6 +112,15 @@ func (cd *Discovery) watchServices(update chan<- *consulService, done <-chan str
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WaitIndex: lastIndex,
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WaitTime: watchTimeout,
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})
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// We have to check the context at least once. The checks during channel sends
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// do not guarantee that.
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select {
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case <-ctx.Done():
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return
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default:
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}
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if err != nil {
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log.Errorf("Error refreshing service list: %s", err)
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time.Sleep(retryInterval)
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@ -174,74 +132,100 @@ func (cd *Discovery) watchServices(update chan<- *consulService, done <-chan str
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}
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lastIndex = meta.LastIndex
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cd.mu.Lock()
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// Check for new services.
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for name := range srvs {
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// If no restriction on scraped services is set, we scrape everything.
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if _, ok := cd.scrapedServices[name]; len(cd.scrapedServices) > 0 && !ok {
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continue
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}
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if _, ok := services[name]; ok {
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continue // We are already watching the service.
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}
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srv := &consulService{
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client: cd.client,
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name: name,
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labels: model.LabelSet{
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serviceLabel: model.LabelValue(name),
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datacenterLabel: model.LabelValue(cd.clientDatacenter),
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},
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tagSeparator: cd.tagSeparator,
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}
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wctx, cancel := context.WithCancel(ctx)
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go srv.watch(wctx, ch)
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services[name] = cancel
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}
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// Check for removed services.
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for name, cancel := range services {
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if _, ok := srvs[name]; !ok {
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// Call the watch cancelation function.
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cancel()
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delete(services, name)
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// Send clearing target group.
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select {
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case <-ctx.Done():
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return
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case ch <- []*config.TargetGroup{{Source: name}}:
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}
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}
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}
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}
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}
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// consulService contains data belonging to the same service.
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type consulService struct {
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name string
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labels model.LabelSet
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client *consul.Client
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tagSeparator string
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}
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func (srv *consulService) watch(ctx context.Context, ch chan<- []*config.TargetGroup) {
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catalog := srv.client.Catalog()
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lastIndex := uint64(0)
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for {
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nodes, meta, err := catalog.Service(srv.name, "", &consul.QueryOptions{
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WaitIndex: lastIndex,
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WaitTime: watchTimeout,
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})
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// Check the context before potentially falling in a continue-loop.
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select {
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case <-done:
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cd.mu.Unlock()
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case <-ctx.Done():
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return
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default:
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// Continue.
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}
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// Check for new services.
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for name := range srvs {
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if _, ok := cd.scrapedServices[name]; len(cd.scrapedServices) > 0 && !ok {
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continue
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}
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srv, ok := cd.services[name]
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if !ok {
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srv = &consulService{
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name: name,
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done: make(chan struct{}),
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}
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srv.tgroup.Source = name
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cd.services[name] = srv
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}
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srv.tgroup.Labels = model.LabelSet{
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serviceLabel: model.LabelValue(name),
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datacenterLabel: model.LabelValue(cd.clientDatacenter),
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}
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update <- srv
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}
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// Check for removed services.
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for name, srv := range cd.services {
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if _, ok := srvs[name]; !ok {
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srv.removed = true
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update <- srv
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delete(cd.services, name)
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}
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}
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cd.mu.Unlock()
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}
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}
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// watchService retrieves updates about srv from Consul's service endpoint.
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// On a potential update the resulting target group is sent to ch.
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func (cd *Discovery) watchService(srv *consulService, ch chan<- []*config.TargetGroup) {
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catalog := cd.client.Catalog()
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for {
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nodes, meta, err := catalog.Service(srv.name, "", &consul.QueryOptions{
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WaitIndex: srv.lastIndex,
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WaitTime: watchTimeout,
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})
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if err != nil {
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log.Errorf("Error refreshing service %s: %s", srv.name, err)
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time.Sleep(retryInterval)
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continue
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}
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// If the index equals the previous one, the watch timed out with no update.
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if meta.LastIndex == srv.lastIndex {
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if meta.LastIndex == lastIndex {
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continue
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}
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srv.lastIndex = meta.LastIndex
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srv.tgroup.Targets = make([]model.LabelSet, 0, len(nodes))
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lastIndex = meta.LastIndex
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tgroup := config.TargetGroup{
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Source: srv.name,
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Labels: srv.labels,
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Targets: make([]model.LabelSet, 0, len(nodes)),
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}
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for _, node := range nodes {
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addr := fmt.Sprintf("%s:%d", node.Address, node.ServicePort)
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// We surround the separated list with the separator as well. This way regular expressions
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// in relabeling rules don't have to consider tag positions.
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tags := cd.tagSeparator + strings.Join(node.ServiceTags, cd.tagSeparator) + cd.tagSeparator
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srv.tgroup.Targets = append(srv.tgroup.Targets, model.LabelSet{
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var (
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addr = fmt.Sprintf("%s:%d", node.Address, node.ServicePort)
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// We surround the separated list with the separator as well. This way regular expressions
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// in relabeling rules don't have to consider tag positions.
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tags = srv.tagSeparator + strings.Join(node.ServiceTags, srv.tagSeparator) + srv.tagSeparator
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)
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tgroup.Targets = append(tgroup.Targets, model.LabelSet{
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model.AddressLabel: model.LabelValue(addr),
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addressLabel: model.LabelValue(node.Address),
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nodeLabel: model.LabelValue(node.Node),
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@ -251,20 +235,16 @@ func (cd *Discovery) watchService(srv *consulService, ch chan<- []*config.Target
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serviceIDLabel: model.LabelValue(node.ServiceID),
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})
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}
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cd.mu.Lock()
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// Check context twice to ensure we always catch cancelation.
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select {
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case <-srv.done:
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cd.mu.Unlock()
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case <-ctx.Done():
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return
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default:
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// Continue.
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}
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// TODO(fabxc): do a copy for now to avoid races. The integration
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// needs needs some general cleanup.
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tg := srv.tgroup
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ch <- []*config.TargetGroup{&tg}
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cd.mu.Unlock()
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select {
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case <-ctx.Done():
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return
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case ch <- []*config.TargetGroup{&tgroup}:
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}
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}
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}
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