Redesign EPP Metrics Pipeline to be Model Server Agnostic

cmd/epp/main.go

@@ -38,7 +38,6 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/metrics/filters"
 	"sigs.k8s.io/gateway-api-inference-extension/internal/runnable"
 	backendmetrics "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/backend/metrics"
-	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/backend/vllm"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/datastore"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/metrics"
 	runserver "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/server"
@@ -92,6 +91,17 @@ var (
 		"certPath", "", "The path to the certificate for secure serving. The certificate and private key files "+
 			"are assumed to be named tls.crt and tls.key, respectively. If not set, and secureServing is enabled, "+
 			"then a self-signed certificate is used.")
+	// metric flags
+	totalQueuedRequestsMetric = flag.String("totalQueuedRequestsMetric",
+		"vllm:num_requests_waiting",
+		"Prometheus metric for the number of queued requests.")
+	kvCacheUsagePercentageMetric = flag.String("kvCacheUsagePercentageMetric",
+		"vllm:gpu_cache_usage_perc",
+		"Prometheus metric for the fraction of KV-cache blocks currently in use (from 0 to 1).")
+	// LoRA metrics
+	loraInfoMetric = flag.String("loraInfoMetric",
+		"vllm:lora_requests_info",
+		"Prometheus metric for the LoRA info metrics (must be in vLLM label format).")
 
 	setupLog = ctrl.Log.WithName("setup")
 )
@@ -143,9 +153,21 @@ func run() error {
 
 	ctx := ctrl.SetupSignalHandler()
 
-	pmf := backendmetrics.NewPodMetricsFactory(&vllm.PodMetricsClientImpl{}, *refreshMetricsInterval)
+	// Set up mapper for metric scraping.
+	mapping, err := backendmetrics.NewMetricMapping(
+		*totalQueuedRequestsMetric,
+		*kvCacheUsagePercentageMetric,
+		*loraInfoMetric,
+	)
+	if err != nil {
+		setupLog.Error(err, "Failed to create metric mapping from flags.")
+		return err
+	}
+
+	pmf := backendmetrics.NewPodMetricsFactory(&backendmetrics.PodMetricsClientImpl{MetricMapping: mapping}, *refreshMetricsInterval)
 	// Setup runner.
 	datastore := datastore.NewDatastore(ctx, pmf)
+
 	serverRunner := &runserver.ExtProcServerRunner{
 		GrpcPort:                                 *grpcPort,
 		DestinationEndpointHintMetadataNamespace: *destinationEndpointHintMetadataNamespace,

pkg/epp/backend/metrics/metrics.go

@@ -0,0 +1,245 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package metrics
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+
+	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
+	"go.uber.org/multierr"
+)
+
+const (
+	// LoRA metrics based on protocol
+	LoraInfoRunningAdaptersMetricName = "running_lora_adapters"
+	LoraInfoWaitingAdaptersMetricName = "waiting_lora_adapters"
+	LoraInfoMaxAdaptersMetricName     = "max_lora"
+)
+
+type PodMetricsClientImpl struct {
+	MetricMapping *MetricMapping
+}
+
+// FetchMetrics fetches metrics from a given pod.
+func (p *PodMetricsClientImpl) FetchMetrics(
+	ctx context.Context,
+	pod *Pod,
+	existing *Metrics,
+	port int32,
+) (*Metrics, error) {
+
+	// Currently the metrics endpoint is hard-coded, which works with vLLM.
+	// TODO(https://github.com/kubernetes-sigs/gateway-api-inference-extension/issues/16): Consume this from InferencePool config.
+	url := "http://" + pod.Address + ":" + strconv.Itoa(int(port)) + "/metrics"
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %v", err)
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch metrics from %s: %w", pod.NamespacedName, err)
+	}
+	defer func() {
+		_ = resp.Body.Close()
+	}()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code from %s: %v", pod.NamespacedName, resp.StatusCode)
+	}
+
+	parser := expfmt.TextParser{}
+	metricFamilies, err := parser.TextToMetricFamilies(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	return p.promToPodMetrics(metricFamilies, existing)
+}
+
+// promToPodMetrics updates internal pod metrics with scraped Prometheus metrics.
+func (p *PodMetricsClientImpl) promToPodMetrics(
+	metricFamilies map[string]*dto.MetricFamily,
+	existing *Metrics,
+) (*Metrics, error) {
+	var errs error
+	updated := existing.Clone()
+
+	if p.MetricMapping.TotalQueuedRequests != nil {
+		queued, err := p.getMetric(metricFamilies, *p.MetricMapping.TotalQueuedRequests)
+		if err == nil {
+			updated.WaitingQueueSize = int(queued.GetGauge().GetValue())
+		} else {
+			errs = multierr.Append(errs, err)
+		}
+	}
+
+	if p.MetricMapping.KVCacheUtilization != nil {
+		usage, err := p.getMetric(metricFamilies, *p.MetricMapping.KVCacheUtilization)
+		if err == nil {
+			updated.KVCacheUsagePercent = usage.GetGauge().GetValue()
+		} else {
+			errs = multierr.Append(errs, err)
+		}
+	}
+
+	// Handle LoRA metrics (only if all LoRA MetricSpecs are present)
+	if p.MetricMapping.LoraRequestInfo != nil {
+		loraMetrics, err := p.getLatestLoraMetric(metricFamilies)
+		errs = multierr.Append(errs, err)
+
+		if loraMetrics != nil {
+			updated.ActiveModels = make(map[string]int)
+			for _, label := range loraMetrics.GetLabel() {
+				if label.GetName() == LoraInfoRunningAdaptersMetricName {
+					if label.GetValue() != "" {
+						adapterList := strings.Split(label.GetValue(), ",")
+						for _, adapter := range adapterList {
+							updated.ActiveModels[adapter] = 0
+						}
+					}
+				}
+				if label.GetName() == LoraInfoWaitingAdaptersMetricName {
+					if label.GetValue() != "" {
+						adapterList := strings.Split(label.GetValue(), ",")
+						for _, adapter := range adapterList {
+							updated.ActiveModels[adapter] = 0
+						}
+					}
+				}
+				if label.GetName() == LoraInfoMaxAdaptersMetricName {
+					if label.GetValue() != "" {
+						updated.MaxActiveModels, err = strconv.Atoi(label.GetValue())
+						if err != nil {
+							errs = multierr.Append(errs, err)
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return updated, errs
+}
+
+// getLatestLoraMetric gets latest lora metric series in gauge metric family `vllm:lora_requests_info`
+// reason its specially fetched is because each label key value pair permutation generates new series
+// and only most recent is useful. The value of each series is the creation timestamp so we can
+// retrieve the latest by sorting the value.
+func (p *PodMetricsClientImpl) getLatestLoraMetric(metricFamilies map[string]*dto.MetricFamily) (*dto.Metric, error) {
+	if p.MetricMapping.LoraRequestInfo == nil {
+		return nil, nil // No LoRA metrics configured
+	}
+
+	loraRequests, ok := metricFamilies[p.MetricMapping.LoraRequestInfo.MetricName]
+	if !ok {
+		return nil, fmt.Errorf("metric family %q not found", p.MetricMapping.LoraRequestInfo.MetricName)
+	}
+
+	var latest *dto.Metric
+	var latestTs float64 // Use float64, as Gauge.Value is float64
+
+	// Iterate over all metrics in the family.
+	for _, m := range loraRequests.GetMetric() {
+		running := ""
+		waiting := ""
+		// Check if the metric has the expected LoRA labels.
+		for _, lp := range m.GetLabel() {
+			switch lp.GetName() {
+			case LoraInfoRunningAdaptersMetricName:
+				running = lp.GetValue()
+			case LoraInfoWaitingAdaptersMetricName:
+				waiting = lp.GetValue()
+			}
+		}
+		// Ignore metrics with both labels empty.
+		if running == "" && waiting == "" {
+			continue
+		}
+
+		// Select the metric with the *largest Gauge Value* (which represents the timestamp).
+		if m.GetGauge().GetValue() > latestTs {
+			latestTs = m.GetGauge().GetValue()
+			latest = m
+		}
+	}
+	if latest == nil {
+		return nil, nil
+	}
+
+	return latest, nil // Convert nanoseconds to time.Time
+}
+
+// getMetric retrieves a specific metric based on MetricSpec.
+func (p *PodMetricsClientImpl) getMetric(metricFamilies map[string]*dto.MetricFamily, spec MetricSpec) (*dto.Metric, error) {
+	mf, ok := metricFamilies[spec.MetricName]
+	if !ok {
+		return nil, fmt.Errorf("metric family %q not found", spec.MetricName)
+	}
+
+	if len(mf.GetMetric()) == 0 {
+		return nil, fmt.Errorf("no metrics available for %q", spec.MetricName)
+	}
+
+	return getLatestMetric(mf, &spec)
+}
+
+// getLabeledMetric gets the latest metric with matching labels.
+func getLatestMetric(mf *dto.MetricFamily, spec *MetricSpec) (*dto.Metric, error) {
+	var latestMetric *dto.Metric
+	var latestTimestamp int64 = -1 // Initialize to -1 so any timestamp is greater
+
+	for _, m := range mf.GetMetric() {
+		if spec.Labels == nil || labelsMatch(m.GetLabel(), spec.Labels) {
+			if m.GetTimestampMs() > latestTimestamp {
+				latestTimestamp = m.GetTimestampMs()
+				latestMetric = m
+			}
+		}
+	}
+
+	if latestMetric != nil {
+		return latestMetric, nil
+	}
+
+	return nil, fmt.Errorf("no matching metric found for %q with labels %+v", spec.MetricName, spec.Labels)
+}
+
+// labelsMatch checks if a metric's labels contain all the labels in the spec.
+func labelsMatch(metricLabels []*dto.LabelPair, specLabels map[string]string) bool {
+	if len(specLabels) == 0 {
+		return true // No specific labels required
+	}
+
+	for specName, specValue := range specLabels {
+		found := false
+		for _, label := range metricLabels {
+			if label.GetName() == specName && label.GetValue() == specValue {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false // A required label is missing
+		}
+	}
+	return true // All required labels are present
+}