feat: add nsq scaler

CHANGELOG.md

@@ -55,6 +55,8 @@ To learn more about active deprecations, we recommend checking [GitHub Discussio
 
 ## Unreleased
 
+- **General:** Introduce new NSQ Scaler ([#3281](https://github.com/kedacore/keda/issues/3281))
+
 ### New
 
 - **General**: Cache miss fallback in validating webhook for ScaledObjects with direct kubernetes client ([#5973](https://github.com/kedacore/keda/issues/5973))

pkg/scalers/nsq_scaler.go

@@ -0,0 +1,358 @@
+package scalers
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+	"sync"
+
+	"github.com/go-logr/logr"
+	v2 "k8s.io/api/autoscaling/v2"
+	"k8s.io/metrics/pkg/apis/external_metrics"
+
+	"github.com/kedacore/keda/v2/pkg/scalers/scalersconfig"
+	kedautil "github.com/kedacore/keda/v2/pkg/util"
+)
+
+type nsqScaler struct {
+	metricType v2.MetricTargetType
+	metadata   nsqMetadata
+	httpClient *http.Client
+	logger     logr.Logger
+}
+
+type nsqMetadata struct {
+	NSQLookupdHTTPAddresses  []string `keda:"name=nsqLookupdHTTPAddresses,  order=triggerMetadata;resolvedEnv"`
+	Topic                    string   `keda:"name=topic,                    order=triggerMetadata;resolvedEnv"`
+	Channel                  string   `keda:"name=channel,                  order=triggerMetadata;resolvedEnv"`
+	DepthThreshold           int64    `keda:"name=depthThreshold,           order=triggerMetadata;resolvedEnv, default=10"`
+	ActivationDepthThreshold int64    `keda:"name=activationDepthThreshold, order=triggerMetadata;resolvedEnv, default=0"`
+
+	triggerIndex int
+}
+
+const (
+	nsqMetricType = "External"
+)
+
+func NewNSQScaler(config *scalersconfig.ScalerConfig) (Scaler, error) {
+	metricType, err := GetMetricTargetType(config)
+	if err != nil {
+		return nil, fmt.Errorf("error getting scaler metric type: %w", err)
+	}
+
+	logger := InitializeLogger(config, "nsq_scaler")
+
+	nsqMetadata, err := parseNSQMetadata(config)
+	if err != nil {
+		return nil, fmt.Errorf("error parsing NSQ metadata: %w", err)
+	}
+
+	return &nsqScaler{
+		metricType: metricType,
+		metadata:   nsqMetadata,
+		httpClient: kedautil.CreateHTTPClient(config.GlobalHTTPTimeout, true),
+		logger:     logger,
+	}, nil
+}
+
+func (m nsqMetadata) Validate() error {
+	if len(m.NSQLookupdHTTPAddresses) == 0 {
+		return fmt.Errorf("no nsqLookupdHTTPAddresses given")
+	}
+
+	if m.Topic == "" {
+		return fmt.Errorf("no topic given")
+	}
+
+	if m.Channel == "" {
+		return fmt.Errorf("no channel given")
+	}
+
+	if m.DepthThreshold <= 0 {
+		return fmt.Errorf("depthThreshold must be a positive integer")
+	}
+
+	if m.ActivationDepthThreshold < 0 {
+		return fmt.Errorf("activationDepthThreshold must be greater than or equal to 0")
+	}
+
+	return nil
+}
+
+func parseNSQMetadata(config *scalersconfig.ScalerConfig) (nsqMetadata, error) {
+	meta := nsqMetadata{triggerIndex: config.TriggerIndex}
+	if err := config.TypedConfig(&meta); err != nil {
+		return meta, fmt.Errorf("error parsing nsq metadata: %w", err)
+	}
+
+	return meta, nil
+}
+
+func (s nsqScaler) GetMetricsAndActivity(_ context.Context, metricName string) ([]external_metrics.ExternalMetricValue, bool, error) {
+	depth, err := s.getTopicChannelDepth()
+
+	if err != nil {
+		return []external_metrics.ExternalMetricValue{}, false, err
+	}
+
+	s.logger.Info("GetMetricsAndActivity", "metricName", metricName, "depth", depth)
+
+	metric := GenerateMetricInMili(metricName, float64(depth))
+
+	return []external_metrics.ExternalMetricValue{metric}, depth > s.metadata.ActivationDepthThreshold, nil
+}
+
+func (s nsqScaler) getTopicChannelDepth() (int64, error) {
+	nsqdHosts, err := s.getTopicProducers(s.metadata.Topic)
+	if err != nil {
+		return -1, fmt.Errorf("error getting nsqd hosts: %w", err)
+	}
+
+	if len(nsqdHosts) == 0 {
+		s.logger.Info("no nsqd hosts found for topic", "topic", s.metadata.Topic)
+		return 0, nil
+	}
+
+	depth, err := s.aggregateDepth(nsqdHosts, s.metadata.Topic, s.metadata.Channel)
+	if err != nil {
+		return -1, fmt.Errorf("error getting topic/channel depth: %w", err)
+	}
+
+	return depth, nil
+}
+
+func (s nsqScaler) GetMetricSpecForScaling(context.Context) []v2.MetricSpec {
+	metricName := fmt.Sprintf("nsq-%s-%s", s.metadata.Topic, s.metadata.Channel)
+
+	externalMetric := &v2.ExternalMetricSource{
+		Metric: v2.MetricIdentifier{
+			Name: GenerateMetricNameWithIndex(s.metadata.triggerIndex, kedautil.NormalizeString(metricName)),
+		},
+		Target: GetMetricTarget(s.metricType, s.metadata.DepthThreshold),
+	}
+	metricSpec := v2.MetricSpec{External: externalMetric, Type: nsqMetricType}
+	return []v2.MetricSpec{metricSpec}
+}
+
+func (s nsqScaler) Close(context.Context) error {
+	if s.httpClient != nil {
+		s.httpClient.CloseIdleConnections()
+	}
+	return nil
+}
+
+type lookupResponse struct {
+	Producers []struct {
+		HTTPPort         int    `json:"http_port"`
+		BroadcastAddress string `json:"broadcast_address"`
+	}
+}
+
+type lookupResult struct {
+	host           string
+	lookupResponse *lookupResponse
+	err            error
+}
+
+func (s *nsqScaler) getTopicProducers(topic string) ([]string, error) {
+	var wg sync.WaitGroup
+	resultCh := make(chan lookupResult, len(s.metadata.NSQLookupdHTTPAddresses))
+
+	for _, host := range s.metadata.NSQLookupdHTTPAddresses {
+		wg.Add(1)
+		go func(host string, topic string) {
+			defer wg.Done()
+			resp, err := s.getLookup(host, topic)
+			resultCh <- lookupResult{host, resp, err}
+		}(host, topic)
+	}
+
+	wg.Wait()
+	close(resultCh)
+
+	var nsqdHostMap = make(map[string]bool)
+	for result := range resultCh {
+		if result.err != nil {
+			return nil, fmt.Errorf("error getting lookup from host '%s': %w", result.host, result.err)
+		}
+
+		if result.lookupResponse == nil {
+			// topic is not found on a single nsqlookupd host, it may exist on another
+			continue
+		}
+
+		for _, producer := range result.lookupResponse.Producers {
+			nsqdHost := net.JoinHostPort(producer.BroadcastAddress, strconv.Itoa(producer.HTTPPort))
+			nsqdHostMap[nsqdHost] = true
+		}
+	}
+
+	var nsqdHosts []string
+	for nsqdHost := range nsqdHostMap {
+		nsqdHosts = append(nsqdHosts, nsqdHost)
+	}
+
+	return nsqdHosts, nil
+}
+
+func (s *nsqScaler) getLookup(host string, topic string) (*lookupResponse, error) {
+	req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/%s", host, "lookup"), nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Accept", "application/json; charset=utf-8")
+
+	params := url.Values{"topic": {topic}}
+	req.URL.RawQuery = params.Encode()
+
+	resp, err := s.httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == http.StatusNotFound {
+		return nil, nil
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code '%s'", resp.Status)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var lookupResponse lookupResponse
+	err = json.Unmarshal(body, &lookupResponse)
+	if err != nil {
+		return nil, err
+	}
+
+	return &lookupResponse, nil
+}
+
+type statsResponse struct {
+	Topics []struct {
+		TopicName string `json:"topic_name"`
+		Depth     int64  `json:"depth"`
+		Channels  []struct {
+			ChannelName string `json:"channel_name"`
+			Depth       int64  `json:"depth"`  // num messages in the queue (mem + disk)
+			Paused      bool   `json:"paused"` // if paused, consumers will not receive messages
+		}
+	}
+}
+
+type statsResult struct {
+	host          string
+	statsResponse *statsResponse
+	err           error
+}
+
+func (s *nsqScaler) aggregateDepth(nsqdHosts []string, topic string, channel string) (int64, error) {
+	wg := sync.WaitGroup{}
+	resultCh := make(chan statsResult, len(nsqdHosts))
+
+	for _, host := range nsqdHosts {
+		wg.Add(1)
+		go func(host string, topic string) {
+			defer wg.Done()
+			resp, err := s.getStats(host, topic)
+			resultCh <- statsResult{host, resp, err}
+		}(host, topic)
+	}
+
+	wg.Wait()
+	close(resultCh)
+
+	var depth int64
+	for result := range resultCh {
+		if result.err != nil {
+			return -1, fmt.Errorf("error getting stats from host '%s': %w", result.host, result.err)
+		}
+
+		for _, t := range result.statsResponse.Topics {
+			if t.TopicName != topic {
+				// this should never happen as we make the /stats call with the "topic" param
+				continue
+			}
+
+			if len(t.Channels) == 0 {
+				// topic exists with no channels, but there are messages in the topic -> we should still scale to bootstrap
+				s.logger.Info("no channels exist for topic", "topic", topic, "channel", channel, "host", result.host)
+				depth += t.Depth
+				continue
+			}
+
+			channelExists := false
+			for _, ch := range t.Channels {
+				if ch.ChannelName != channel {
+					continue
+				}
+				channelExists = true
+				if ch.Paused {
+					// if it's paused on a single nsqd host, it's depth should not go into the aggregate
+					// meaning if paused on all nsqd hosts => depth == 0
+					s.logger.Info("channel is paused", "topic", topic, "channel", channel, "host", result.host)
+					continue
+				}
+				depth += ch.Depth
+			}
+			if !channelExists {
+				// topic exists with channels, but not the one in question - fallback to topic depth
+				s.logger.Info("channel does not exist for topic", "topic", topic, "channel", channel, "host", result.host)
+				depth += t.Depth
+			}
+		}
+	}
+
+	return depth, nil
+}
+
+func (s *nsqScaler) getStats(host string, topic string) (*statsResponse, error) {
+	req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/%s", host, "stats"), nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// "channel" is a query param as well, but if used and the channel does not exist
+	// we do not receive any stats for the existing topic
+	params := url.Values{
+		"format":          {"json"},
+		"include_clients": {"false"},
+		"include_mem":     {"false"},
+		"topic":           {topic},
+	}
+	req.URL.RawQuery = params.Encode()
+
+	resp, err := s.httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code '%s'", resp.Status)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var statsResponse statsResponse
+	err = json.Unmarshal(body, &statsResponse)
+	if err != nil {
+		return nil, err
+	}
+
+	return &statsResponse, nil
+}