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watch.go
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watch.go
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package consulagent
import (
"context"
"encoding/json"
"errors"
"flag"
"fmt"
"net/url"
"sync"
"time"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discovery/consul"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discoveryutils"
"github.com/VictoriaMetrics/metrics"
)
// SDCheckInterval is check interval for Consul Agent service discovery.
var SDCheckInterval = flag.Duration("promscrape.consulagentSDCheckInterval", 30*time.Second, "Interval for checking for changes in Consul Agent. "+
"This works only if consulagent_sd_configs is configured in '-promscrape.config' file. "+
"See https://docs.victoriametrics.com/sd_configs.html#consulagent_sd_configs for details")
// consulAgentWatcher is a watcher for consul api, updates services map in background with long-polling.
type consulAgentWatcher struct {
client *discoveryutils.Client
servicesQueryArgs string
watchServices []string
watchDatacenter string
// servicesLock protects services
servicesLock sync.Mutex
services map[string]*serviceWatcher
stoppedCh chan struct{}
}
type serviceWatcher struct {
serviceName string
serviceNodes []consul.ServiceNode
stoppedCh chan struct{}
requestCtx context.Context
requestCancel context.CancelFunc
}
// newConsulAgentWatcher creates new watcher and starts background service discovery for Consul.
func newConsulAgentWatcher(client *discoveryutils.Client, sdc *SDConfig, datacenter, namespace string) *consulAgentWatcher {
var qv = url.Values{}
if namespace != "" {
qv.Set("ns", namespace)
}
if len(sdc.Filter) > 0 {
qv.Set("filter", sdc.Filter)
}
cw := &consulAgentWatcher{
client: client,
servicesQueryArgs: "?" + qv.Encode(),
watchServices: sdc.Services,
watchDatacenter: datacenter,
services: make(map[string]*serviceWatcher),
stoppedCh: make(chan struct{}),
}
initCh := make(chan struct{})
go func() {
cw.watchForServicesUpdates(initCh)
close(cw.stoppedCh)
}()
// wait for initialization to complete
<-initCh
return cw
}
func (cw *consulAgentWatcher) mustStop() {
cw.client.Stop()
<-cw.stoppedCh
}
func (cw *consulAgentWatcher) updateServices(serviceNames []string) {
var initWG sync.WaitGroup
// Start watchers for new services.
cw.servicesLock.Lock()
for _, serviceName := range serviceNames {
if _, ok := cw.services[serviceName]; ok {
// The watcher for serviceName already exists.
continue
}
ctx, cancel := context.WithCancel(cw.client.Context())
sw := &serviceWatcher{
serviceName: serviceName,
stoppedCh: make(chan struct{}),
requestCtx: ctx,
requestCancel: cancel,
}
cw.services[serviceName] = sw
serviceWatchersCreated.Inc()
initWG.Add(1)
go func() {
serviceWatchersCount.Inc()
sw.watchForServiceNodesUpdates(cw, &initWG)
serviceWatchersCount.Dec()
close(sw.stoppedCh)
}()
}
// Stop watchers for removed services.
newServiceNamesMap := make(map[string]struct{}, len(serviceNames))
for _, serviceName := range serviceNames {
newServiceNamesMap[serviceName] = struct{}{}
}
var swsStopped []*serviceWatcher
for serviceName, sw := range cw.services {
if _, ok := newServiceNamesMap[serviceName]; ok {
continue
}
sw.requestCancel()
delete(cw.services, serviceName)
swsStopped = append(swsStopped, sw)
}
cw.servicesLock.Unlock()
// Wait until deleted service watchers are stopped.
for _, sw := range swsStopped {
<-sw.stoppedCh
serviceWatchersStopped.Inc()
}
// Wait until added service watchers are initialized.
initWG.Wait()
}
// watchForServicesUpdates watches for new services and updates it in cw.
//
// watchForServicesUpdates closes the initCh once the initialization is complete and first discovery iteration is done.
func (cw *consulAgentWatcher) watchForServicesUpdates(initCh chan struct{}) {
apiServer := cw.client.APIServer()
f := func() {
serviceNames, err := cw.getServiceNames()
if err != nil {
if !errors.Is(err, context.Canceled) {
logger.Errorf("cannot obtain Consul Agent services from %q: %s", apiServer, err)
}
return
}
cw.updateServices(serviceNames)
}
logger.Infof("started Consul Agent service watcher for %q", apiServer)
f()
// send signal that initialization is complete
close(initCh)
ticker := time.NewTicker(getCheckInterval())
defer ticker.Stop()
stopCh := cw.client.Context().Done()
for {
select {
case <-ticker.C:
f()
case <-stopCh:
logger.Infof("stopping Consul Agent service watchers for %q", apiServer)
startTime := time.Now()
var swsStopped []*serviceWatcher
cw.servicesLock.Lock()
for _, sw := range cw.services {
sw.requestCancel()
swsStopped = append(swsStopped, sw)
}
cw.servicesLock.Unlock()
for _, sw := range swsStopped {
<-sw.stoppedCh
serviceWatchersStopped.Inc()
}
logger.Infof("stopped Consul Agent service watcher for %q in %.3f seconds", apiServer, time.Since(startTime).Seconds())
return
}
}
}
var (
serviceWatchersCreated = metrics.NewCounter("vm_promscrape_discovery_consulagent_service_watchers_created_total")
serviceWatchersStopped = metrics.NewCounter("vm_promscrape_discovery_consulagent_service_watchers_stopped_total")
serviceWatchersCount = metrics.NewCounter("vm_promscrape_discovery_consulagent_service_watchers")
)
// getServiceNames obtains serviceNames via request to Consul Agent.
//
// It returns an empty serviceNames list if response contains the same index.
func (cw *consulAgentWatcher) getServiceNames() ([]string, error) {
path := "/v1/agent/services" + cw.servicesQueryArgs
data, err := cw.client.GetAPIResponse(path)
if err != nil {
return nil, fmt.Errorf("cannot perform Consul Agent API request at %q: %w", path, err)
}
var m map[string]consul.Service
if err := json.Unmarshal(data, &m); err != nil {
return nil, fmt.Errorf("cannot parse response from %q: %w; data=%q", path, err, data)
}
serviceNames := make([]string, 0, len(m))
for _, service := range m {
serviceName := service.Service
if service.Datacenter != cw.watchDatacenter {
continue
}
if !consul.ShouldCollectServiceByName(cw.watchServices, serviceName) {
continue
}
serviceNames = append(serviceNames, serviceName)
}
return serviceNames, nil
}
// watchForServiceNodesUpdates watches for Consul serviceNode changes for the given serviceName.
//
// watchForServiceNodesUpdates calls initWG.Done() once the initialization is complete and the first discovery iteration is done.
func (sw *serviceWatcher) watchForServiceNodesUpdates(cw *consulAgentWatcher, initWG *sync.WaitGroup) {
apiServer := cw.client.APIServer()
path := "/v1/agent/health/service/name/" + sw.serviceName
f := func() {
data, err := cw.client.GetAPIResponseWithParamsCtx(sw.requestCtx, path, nil, nil)
if err != nil {
if !errors.Is(err, context.Canceled) {
logger.Errorf("cannot obtain Consul Agent serviceNodes for serviceName=%q from %q: %s", sw.serviceName, apiServer, err)
}
return
}
sns, err := consul.ParseServiceNodes(data)
if err != nil {
logger.Errorf("cannot parse Consul Agent serviceNodes response for serviceName=%q from %q: %s", sw.serviceName, apiServer, err)
return
}
cw.servicesLock.Lock()
sw.serviceNodes = sns
cw.servicesLock.Unlock()
}
f()
// Notify caller that initialization is complete
initWG.Done()
ticker := time.NewTicker(getCheckInterval())
defer ticker.Stop()
stopCh := sw.requestCtx.Done()
for {
select {
case <-ticker.C:
f()
case <-stopCh:
return
}
}
}
// getServiceNodesSnapshot returns a snapshot of discovered ServiceNodes.
func (cw *consulAgentWatcher) getServiceNodesSnapshot() map[string][]consul.ServiceNode {
cw.servicesLock.Lock()
sns := make(map[string][]consul.ServiceNode, len(cw.services))
for svc, sw := range cw.services {
sns[svc] = sw.serviceNodes
}
cw.servicesLock.Unlock()
return sns
}
func getCheckInterval() time.Duration {
d := *SDCheckInterval
if d <= time.Second {
return time.Second
}
return d
}