lib/promscrape: code cleanup after c6dee6c52d

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/574

docs/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 # tip
 
+* FEATURE: optimize Consul service discovery speed when discovering big number of services. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/574
+
 * BUGFIX: properly parse timestamps in OpenMetrics format - they are exposed as floating-point number in seconds instead of integer milliseconds
   unlike in Prometheus exposition format. See [the docs](https://github.com/OpenObservability/OpenMetrics/blob/master/specification/OpenMetrics.md#timestamps).
 * BUGFIX: return `nan` for `a >bool b` query when `a` equals to `nan` like Prometheus does. Previously `0` was returned in this case. This applies to any comparison operation

lib/promscrape/discovery/consul/api.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
@@ -13,11 +14,10 @@ import (
 	"github.com/VictoriaMetrics/fasthttp"
 )
 
-// apiConfig contains config for API server
-// with consulWatch service.
+// apiConfig contains config for API server.
 type apiConfig struct {
 	tagSeparator  string
-	consulWatcher *consulWatch
+	consulWatcher *consulWatcher
 }
 
 var configMap = discoveryutils.NewConfigMap()
@@ -71,10 +71,7 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 		return nil, err
 	}
 
-	cw, err := newConsulWatch(client, sdc, dc)
-	if err != nil {
-		return nil, fmt.Errorf("cannot start consul watcher: %w", err)
-	}
+	cw := newConsulWatcher(client, sdc, dc)
 	cfg := &apiConfig{
 		tagSeparator:  tagSeparator,
 		consulWatcher: cw,
@@ -114,35 +111,28 @@ func getDatacenter(client *discoveryutils.Client, dc string) (string, error) {
 	return a.Config.Datacenter, nil
 }
 
-// returns ServiceNodesState and version index.
-func getServiceState(client *discoveryutils.Client, svc, baseArgs string, index uint64) ([]ServiceNode, uint64, error) {
-	path := fmt.Sprintf("/v1/health/service/%s%s", svc, baseArgs)
-
-	data, newIndex, err := getBlockingAPIResponse(client, path, index)
-	if err != nil {
-		return nil, index, err
-	}
-	sns, err := parseServiceNodes(data)
-	if err != nil {
-		return nil, index, err
-	}
-	return sns, newIndex, nil
-}
-
-// returns consul api response with new index version of object.
+// maxWaitTime is duration for consul blocking request, maximum wait time is 10 min.
+// But fasthttp client has readTimeout for 1 min, so we use 50s timeout.
+// also consul adds random delay up to wait/16, so there is no need in jitter.
 // https://www.consul.io/api-docs/features/blocking
-func getBlockingAPIResponse(client *discoveryutils.Client, path string, index uint64) ([]byte, uint64, error) {
-	path += "&index=" + strconv.FormatUint(index, 10)
-	path = path + fmt.Sprintf("&wait=%s", watchTime)
+const maxWaitTime = 50 * time.Second
+
+var maxWaitTimeStr = maxWaitTime.String()
+
+// getBlockingAPIResponse perfoms blocking request to Consul via client and returns response.
+//
+// See https://www.consul.io/api-docs/features/blocking .
+func getBlockingAPIResponse(client *discoveryutils.Client, path string, index int64) ([]byte, int64, error) {
+	path += "&index=" + strconv.FormatInt(index, 10)
+	path += "&wait=" + maxWaitTimeStr
 	getMeta := func(resp *fasthttp.Response) {
 		if ind := resp.Header.Peek("X-Consul-Index"); len(ind) > 0 {
-			newIndex, err := strconv.ParseUint(string(ind), 10, 64)
+			newIndex, err := strconv.ParseInt(string(ind), 10, 64)
 			if err != nil {
-				logger.Errorf("failed to parse consul index: %v", err)
+				logger.Errorf("cannot parse X-Consul-Index header value in response from %q: %s", path, err)
 				return
 			}
-			// reset index
-			// https://www.consul.io/api-docs/features/blocking#implementation-details
+			// Properly handle the returned newIndex according to https://www.consul.io/api-docs/features/blocking#implementation-details
 			if newIndex < 1 {
 				index = 1
 				return
@@ -156,7 +146,7 @@ func getBlockingAPIResponse(client *discoveryutils.Client, path string, index ui
 	}
 	data, err := client.GetBlockingAPIResponse(path, getMeta)
 	if err != nil {
-		return nil, index, fmt.Errorf("failed query consul api path=%q, err=%w", path, err)
+		return nil, index, fmt.Errorf("cannot perform blocking Consul API request at %q: %w", path, err)
 	}
 	return data, index, nil
 }

lib/promscrape/discovery/consul/consul.go

@@ -1,25 +1,11 @@
 package consul
 
 import (
-	"flag"
 	"fmt"
-	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
 )
 
-var (
-	// SDCheckInterval - check interval for consul discovery.
-	SDCheckInterval = flag.Duration("promscrape.consulSDCheckInterval", 30*time.Second, "Interval for checking for changes in consul. "+
-		"This works only if `consul_sd_configs` is configured in '-promscrape.config' file. "+
-		"See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#consul_sd_config for details")
-	// duration for consul blocking request, maximum wait time is 10 min.
-	// But fasthttp client has readTimeout for 1 min, so we use 50s timeout.
-	// also consul adds random delay up to wait/16, so there is no need in jitter.
-	// https://www.consul.io/api-docs/features/blocking
-	watchTime = time.Second * 50
-)
-
 // SDConfig represents service discovery config for Consul.
 //
 // See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#consul_sd_config
@@ -46,9 +32,6 @@ func GetLabels(sdc *SDConfig, baseDir string) ([]map[string]string, error) {
 	if err != nil {
 		return nil, fmt.Errorf("cannot get API config: %w", err)
 	}
-	ms, err := getServiceNodesLabels(cfg)
-	if err != nil {
-		return nil, fmt.Errorf("error when fetching service nodes data from Consul: %w", err)
-	}
+	ms := getServiceNodesLabels(cfg)
 	return ms, nil
 }

lib/promscrape/discovery/consul/service_node.go

@@ -9,14 +9,14 @@ import (
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discoveryutils"
 )
 
-// getServiceNodesLabels returns labels for Consul service nodes with given tagSeparator.
-func getServiceNodesLabels(cfg *apiConfig) ([]map[string]string, error) {
-	sns := cfg.consulWatcher.getServiceNodes()
+// getServiceNodesLabels returns labels for Consul service nodes with given cfg.
+func getServiceNodesLabels(cfg *apiConfig) []map[string]string {
+	sns := cfg.consulWatcher.getServiceNodesSnapshot()
 	var ms []map[string]string
 	for _, sn := range sns {
 		ms = sn.appendTargetLabels(ms, cfg.tagSeparator)
 	}
-	return ms, nil
+	return ms
 }
 
 // ServiceNode is Consul service node.

lib/promscrape/discovery/consul/watch.go

@@ -2,213 +2,250 @@ package consul
 
 import (
 	"encoding/json"
+	"flag"
 	"fmt"
 	"net/url"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discoveryutils"
+	"github.com/VictoriaMetrics/metrics"
 )
 
-type serviceWatch struct {
-	stopCh       chan struct{}
-	serviceNodes []ServiceNode
-}
+// SDCheckInterval is check interval for Consul service discovery.
+var SDCheckInterval = flag.Duration("promscrape.consulSDCheckInterval", 30*time.Second, "Interval for checking for changes in Consul. "+
+	"This works only if `consul_sd_configs` is configured in '-promscrape.config' file. "+
+	"See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#consul_sd_config for details")
 
-// watcher for consul api, updates targets in background with long-polling.
-type consulWatch struct {
-	baseQueryArgs       string
+// consulWatcher is a watcher for consul api, updates services map in background with long-polling.
+type consulWatcher struct {
 	client *discoveryutils.Client
-	lastAccessTime      atomic.Value
-	nodeMeta            string
-	shouldWatchServices []string
-	shouldWatchTags     []string
-	// guards services
+
+	serviceNamesQueryArgs string
+	serviceNodesQueryArgs string
+	watchServices         []string
+	watchTags             []string
+
+	// servicesLock protects services and servicesLastAccessTime
 	servicesLock           sync.Mutex
-	services     map[string]serviceWatch
+	services               map[string]*serviceWatcher
+	servicesLastAccessTime time.Time
+
+	wg sync.WaitGroup
+}
+
+type serviceWatcher struct {
+	serviceName  string
+	serviceNodes []ServiceNode
 	stopCh       chan struct{}
 }
 
-// init new watcher and start background service discovery for Consul.
-func newConsulWatch(client *discoveryutils.Client, sdc *SDConfig, datacenter string) (*consulWatch, error) {
-	baseQueryArgs := fmt.Sprintf("?sdc=%s", url.QueryEscape(datacenter))
-	var nodeMeta string
-	if len(sdc.NodeMeta) > 0 {
-		for k, v := range sdc.NodeMeta {
-			nodeMeta += fmt.Sprintf("&node-meta=%s", url.QueryEscape(k+":"+v))
-		}
-	}
+// newConsulWatcher creates new watcher and start background service discovery for Consul.
+func newConsulWatcher(client *discoveryutils.Client, sdc *SDConfig, datacenter string) *consulWatcher {
+	baseQueryArgs := "?sdc=" + url.QueryEscape(datacenter)
 	if sdc.AllowStale {
 		baseQueryArgs += "&stale"
 	}
-	cw := consulWatch{
+	for k, v := range sdc.NodeMeta {
+		baseQueryArgs += "&node-meta=" + url.QueryEscape(k+":"+v)
+	}
+	serviceNodesQueryArgs := baseQueryArgs
+	for _, tag := range sdc.Tags {
+		serviceNodesQueryArgs += "&tag=" + url.QueryEscape(tag)
+	}
+	cw := &consulWatcher{
 		client:                 client,
-		baseQueryArgs:       baseQueryArgs,
-		shouldWatchServices: sdc.Services,
-		shouldWatchTags:     sdc.Tags,
-		services:            make(map[string]serviceWatch),
+		serviceNamesQueryArgs:  baseQueryArgs,
+		serviceNodesQueryArgs:  serviceNodesQueryArgs,
+		watchServices:          sdc.Services,
+		watchTags:              sdc.Tags,
+		services:               make(map[string]*serviceWatcher),
+		servicesLastAccessTime: time.Now(),
+	}
+	go cw.watchForServicesUpdates()
+	return cw
 }
 
-	watchServiceNames, _, err := cw.getServiceNames(0)
+// watchForServicesUpdates watches for new services and updates it in cw.
+func (cw *consulWatcher) watchForServicesUpdates() {
+	checkInterval := getCheckInterval()
+	ticker := time.NewTicker(checkInterval / 2)
+	defer ticker.Stop()
+	index := int64(0)
+	clientAddr := cw.client.Addr()
+	f := func() {
+		serviceNames, newIndex, err := cw.getBlockingServiceNames(index)
 		if err != nil {
-		return nil, err
+			logger.Errorf("cannot obtain Consul serviceNames from %q: %s", clientAddr, err)
+			return
 		}
-	var wg sync.WaitGroup
+		if index == newIndex {
+			// Nothing changed.
+			return
+		}
+
 		cw.servicesLock.Lock()
-	for serviceName := range watchServiceNames {
-		stopCh := make(chan struct{})
-		cw.services[serviceName] = serviceWatch{stopCh: stopCh}
-		wg.Add(1)
-		go func(serviceName string) {
-			defer wg.Done()
-			cw.watchForServiceUpdates(serviceName, stopCh)
-		}(serviceName)
+		// Start watchers for new services.
+		for _, serviceName := range serviceNames {
+			if _, ok := cw.services[serviceName]; ok {
+				// The watcher for serviceName already exists.
+				continue
+			}
+			sw := &serviceWatcher{
+				serviceName: serviceName,
+				stopCh:      make(chan struct{}),
+			}
+			cw.services[serviceName] = sw
+			cw.wg.Add(1)
+			serviceWatchersCreated.Inc()
+			go func() {
+				serviceWatchersCount.Inc()
+				sw.watchForServiceNodesUpdates(cw)
+				serviceWatchersCount.Dec()
+				cw.wg.Done()
+			}()
+		}
+		// Stop watchers for removed services.
+		newServiceNamesMap := make(map[string]struct{}, len(serviceNames))
+		for _, serviceName := range serviceNames {
+			newServiceNamesMap[serviceName] = struct{}{}
+		}
+		for serviceName, sw := range cw.services {
+			if _, ok := newServiceNamesMap[serviceName]; ok {
+				continue
+			}
+			close(sw.stopCh)
+			delete(cw.services, serviceName)
+			serviceWatchersStopped.Inc()
+
+			// Do not wait for the watcher goroutine to exit, since this may take for up to maxWaitTime
+			// if it is blocked in Consul API request.
 		}
 		cw.servicesLock.Unlock()
-	// wait for first init.
-	wg.Wait()
-	go cw.watchForServices()
-	return &cw, nil
+
+		index = newIndex
 	}
 
-// stops all service watchers.
-func (cw *consulWatch) stopServiceWatchersAll() {
+	logger.Infof("started Consul service watcher for %q", clientAddr)
+	f()
+	for range ticker.C {
+		cw.servicesLock.Lock()
+		lastAccessTime := cw.servicesLastAccessTime
+		cw.servicesLock.Unlock()
+		if time.Since(lastAccessTime) > 3*checkInterval {
+			// The given cw is no longer used. Stop all service watchers and exit.
+			logger.Infof("starting to stop Consul service watchers for %q", clientAddr)
 			cw.servicesLock.Lock()
 			for _, sw := range cw.services {
 				close(sw.stopCh)
 			}
 			cw.servicesLock.Unlock()
+			cw.wg.Wait()
+			logger.Infof("stopped Consul service watcher for %q", clientAddr)
+			return
 		}
 
-// getServiceNames returns serviceNames and index version.
-func (cw *consulWatch) getServiceNames(index uint64) (map[string]struct{}, uint64, error) {
-	sns := make(map[string]struct{})
-	path := fmt.Sprintf("/v1/catalog/services%s", cw.baseQueryArgs)
-	if len(cw.nodeMeta) > 0 {
-		path += cw.nodeMeta
+		f()
 	}
+}
+
+var (
+	serviceWatchersCreated = metrics.NewCounter("vm_promscrape_discovery_consul_service_watchers_created_total")
+	serviceWatchersStopped = metrics.NewCounter("vm_promscrape_discovery_consul_service_watchers_stopped_total")
+	serviceWatchersCount   = metrics.NewCounter("vm_promscrape_discovery_consul_service_watchers")
+)
+
+// getBlockingServiceNames obtains serviceNames via blocking request to Consul.
+//
+// It returns an empty serviceNames list if response contains the same index.
+func (cw *consulWatcher) getBlockingServiceNames(index int64) ([]string, int64, error) {
+	path := "/v1/catalog/services" + cw.serviceNamesQueryArgs
 	data, newIndex, err := getBlockingAPIResponse(cw.client, path, index)
 	if err != nil {
 		return nil, index, err
 	}
+	if index == newIndex {
+		// Nothing changed - return an empty serviceNames list.
+		return nil, index, nil
+	}
 	var m map[string][]string
 	if err := json.Unmarshal(data, &m); err != nil {
-		return nil, index, fmt.Errorf("cannot parse services response=%q, err=%w", data, err)
+		return nil, index, fmt.Errorf("cannot parse response from %q: %w; data=%q", path, err, data)
 	}
-	for k, tags := range m {
-		if !shouldCollectServiceByName(cw.shouldWatchServices, k) {
+	serviceNames := make([]string, 0, len(m))
+	for serviceName, tags := range m {
+		if !shouldCollectServiceByName(cw.watchServices, serviceName) {
 			continue
 		}
-		if !shouldCollectServiceByTags(cw.shouldWatchTags, tags) {
+		if !shouldCollectServiceByTags(cw.watchTags, tags) {
 			continue
 		}
-		sns[k] = struct{}{}
+		serviceNames = append(serviceNames, serviceName)
 	}
-	return sns, newIndex, nil
+	return serviceNames, newIndex, nil
 }
 
-// listen for new services and update it.
-func (cw *consulWatch) watchForServices() {
-	ticker := time.NewTicker(*SDCheckInterval)
+// watchForServiceNodesUpdates watches for Consul serviceNode changes for the given serviceName.
+func (sw *serviceWatcher) watchForServiceNodesUpdates(cw *consulWatcher) {
+	checkInterval := getCheckInterval()
+	ticker := time.NewTicker(checkInterval / 2)
 	defer ticker.Stop()
-	var index uint64
-	for {
-		select {
-		case <-cw.stopCh:
-			cw.stopServiceWatchersAll()
-			return
-		case <-ticker.C:
-			if time.Since(cw.lastAccessTime.Load().(time.Time)) > *SDCheckInterval*2 {
-				// exit watch and stop all background watchers.
-				cw.stopServiceWatchersAll()
-				return
-			}
-			m, newIndex, err := cw.getServiceNames(index)
+	clientAddr := cw.client.Addr()
+	index := int64(0)
+	path := "/v1/health/service/" + sw.serviceName + cw.serviceNodesQueryArgs
+	f := func() {
+		data, newIndex, err := getBlockingAPIResponse(cw.client, path, index)
 		if err != nil {
-				logger.Errorf("failed get serviceNames from consul api: err=%v", err)
-				continue
+			logger.Errorf("cannot obtain Consul serviceNodes for serviceName=%q from %q: %s", sw.serviceName, clientAddr, err)
+			return
 		}
-			// nothing changed.
 		if index == newIndex {
-				continue
+			// Nothing changed.
+			return
 		}
+		sns, err := parseServiceNodes(data)
+		if err != nil {
+			logger.Errorf("cannot parse Consul serviceNodes response for serviceName=%q from %q: %s", sw.serviceName, clientAddr, err)
+			return
+		}
+
 		cw.servicesLock.Lock()
-			// start new services watchers.
-			for svc := range m {
-				if _, ok := cw.services[svc]; !ok {
-					stopCh := make(chan struct{})
-					cw.services[svc] = serviceWatch{stopCh: stopCh}
-					go cw.watchForServiceUpdates(svc, stopCh)
-				}
-			}
-			// stop watch for removed services.
-			for svc, s := range cw.services {
-				if _, ok := m[svc]; !ok {
-					close(s.stopCh)
-					delete(cw.services, svc)
-				}
-			}
+		sw.serviceNodes = sns
 		cw.servicesLock.Unlock()
+
 		index = newIndex
 	}
-	}
 
-}
-
-// start watching for consul service changes.
-func (cw *consulWatch) watchForServiceUpdates(svc string, stopCh chan struct{}) {
-	ticker := time.NewTicker(*SDCheckInterval)
-	defer ticker.Stop()
-	updateServiceState := func(index uint64) uint64 {
-		sns, newIndex, err := getServiceState(cw.client, svc, cw.baseQueryArgs, index)
-		if err != nil {
-			logger.Errorf("failed update service state, service_name=%q, err=%v", svc, err)
-			return index
-		}
-		if newIndex == index {
-			return index
-		}
-		cw.servicesLock.Lock()
-		if s, ok := cw.services[svc]; ok {
-			s.serviceNodes = sns
-			cw.services[svc] = s
-		}
-		cw.servicesLock.Unlock()
-		return newIndex
-	}
-	watchIndex := updateServiceState(0)
-	go func() {
+	f()
 	for {
 		select {
 		case <-ticker.C:
-				watchIndex = updateServiceState(watchIndex)
-			case <-stopCh:
+			f()
+		case <-sw.stopCh:
 			return
 		}
 	}
-	}()
 }
 
-// returns ServiceNodes.
-func (cw *consulWatch) getServiceNodes() []ServiceNode {
+// getServiceNodesSnapshot returns a snapshot of discovered ServiceNodes.
+func (cw *consulWatcher) getServiceNodesSnapshot() []ServiceNode {
 	var sns []ServiceNode
 	cw.servicesLock.Lock()
-	for _, v := range cw.services {
-		sns = append(sns, v.serviceNodes...)
+	for _, sw := range cw.services {
+		sns = append(sns, sw.serviceNodes...)
 	}
+	cw.servicesLastAccessTime = time.Now()
 	cw.servicesLock.Unlock()
-	cw.lastAccessTime.Store(time.Now())
 	return sns
 }
 
-func shouldCollectServiceByName(filterServices []string, service string) bool {
+func shouldCollectServiceByName(filterServices []string, serviceName string) bool {
 	if len(filterServices) == 0 {
 		return true
 	}
 	for _, filterService := range filterServices {
-		if filterService == service {
+		if filterService == serviceName {
 			return true
 		}
 	}
@@ -233,3 +270,11 @@ func shouldCollectServiceByTags(filterTags, tags []string) bool {
 	}
 	return true
 }
+
+func getCheckInterval() time.Duration {
+	d := *SDCheckInterval
+	if d <= time.Second {
+		return time.Second
+	}
+	return d
+}

lib/promscrape/discoveryutils/client.go

@@ -33,9 +33,12 @@ func GetHTTPClient() *http.Client {
 
 // Client is http client, which talks to the given apiServer.
 type Client struct {
+	// hc is used for short requests.
 	hc *fasthttp.HostClient
-	// blockingClient is used for performing long-polling requests.
+
+	// blockingClient is used for long-polling requests.
 	blockingClient *fasthttp.HostClient
+
 	ac        *promauth.Config
 	apiServer string
 	hostPort  string
@@ -82,7 +85,7 @@ func NewClient(apiServer string, ac *promauth.Config) (*Client, error) {
 		MaxConns:            2 * *maxConcurrency,
 		Dial:                dialFunc,
 	}
-	wc := &fasthttp.HostClient{
+	blockingClient := &fasthttp.HostClient{
 		Addr:                hostPort,
 		Name:                "vm_promscrape/discovery",
 		DialDualStack:       netutil.TCP6Enabled(),
@@ -96,7 +99,7 @@ func NewClient(apiServer string, ac *promauth.Config) (*Client, error) {
 	}
 	return &Client{
 		hc:             hc,
-		blockingClient: wc,
+		blockingClient: blockingClient,
 		ac:             ac,
 		apiServer:      apiServer,
 		hostPort:       hostPort,
@@ -112,10 +115,9 @@ func concurrencyLimitChInit() {
 	concurrencyLimitCh = make(chan struct{}, *maxConcurrency)
 }
 
-// APIRequestParams modifies api request with given params.
-type APIRequestParams struct {
-	FetchFromResponse func(resp *fasthttp.Response)
-	SetToRequest      func(req *fasthttp.Request)
+// Addr returns the address the client connects to.
+func (c *Client) Addr() string {
+	return c.hc.Addr
 }
 
 // GetAPIResponse returns response for the given absolute path.