Refactor: Define PodMetricsClient interface and hide implementation details of vllm metrics processing

pkg/ext-proc/backend/fake.go

@@ -1,20 +1,16 @@
 package backend
 
-import (
-	dto "github.com/prometheus/client_model/go"
-)
-
 type FakePodLister struct {
 	Err  error
 	Pods PodSet
 }
 
 type FakePodMetricsClient struct {
 	Err map[Pod]error
-	Res map[Pod]map[string]*dto.MetricFamily
+	Res map[Pod]*PodMetrics
 }
 
-func (f *FakePodMetricsClient) FetchMetrics(pod Pod) (map[string]*dto.MetricFamily, error) {
+func (f *FakePodMetricsClient) FetchMetrics(pod Pod, existing *PodMetrics) (*PodMetrics, error) {
 	if err, ok := f.Err[pod]; ok {
 		return nil, err
 	}

pkg/ext-proc/backend/provider.go

@@ -5,7 +5,7 @@ import (
 	"sync"
 	"time"
 
-	dto "github.com/prometheus/client_model/go"
+	"go.uber.org/multierr"
 	klog "k8s.io/klog/v2"
 )
 
@@ -27,7 +27,7 @@ type Provider struct {
 }
 
 type PodMetricsClient interface {
-	FetchMetrics(pod Pod) (map[string]*dto.MetricFamily, error)
+	FetchMetrics(pod Pod, existing *PodMetrics) (*PodMetrics, error)
 }
 
 type PodLister interface {
@@ -130,3 +130,37 @@ func (p *Provider) refreshPodsOnce() error {
 	p.podMetrics.Range(mergeFn)
 	return nil
 }
+
+func (p *Provider) refreshMetricsOnce() error {
+	start := time.Now()
+	defer func() {
+		d := time.Since(start)
+		// TODO: add a metric instead of logging
+		klog.V(4).Infof("Refreshed metrics in %v", d)
+	}()
+	var wg sync.WaitGroup
+	var errs error
+	processOnePod := func(key, value any) bool {
+		klog.V(4).Infof("Processing pod %v and metric %v", key, value)
+		pod := key.(Pod)
+		existing := value.(*PodMetrics)
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			updated, err := p.pmc.FetchMetrics(pod, existing)
+			if err != nil {
+				multierr.Append(errs, fmt.Errorf("failed to parse metrics from %s: %v", pod, err))
+				return
+			}
+			klog.V(4).Infof("Updated metrics for pod %s: %v", pod, updated.Metrics)
+			if err != nil {
+				multierr.Append(errs, fmt.Errorf("failed to get all pod metrics updated from prometheus: %v", err))
+			}
+			p.UpdatePodMetrics(pod, updated)
+		}()
+		return true
+	}
+	p.podMetrics.Range(processOnePod)
+	wg.Wait()
+	return errs
+}

pkg/ext-proc/backend/metrics.go → pkg/ext-proc/backend/vllm/metrics.go

@@ -1,12 +1,15 @@
-package backend
+// Package vllm provides vllm specific pod metrics implementation.
+package vllm
 
 import (
+	"ext-proc/backend"
 	"fmt"
+	"net/http"
 	"strings"
-	"sync"
 	"time"
 
 	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
 	"go.uber.org/multierr"
 	klog "k8s.io/klog/v2"
 )
@@ -25,45 +28,38 @@ const (
 	KvCacheMaxTokenCapacityMetricName = "vllm:gpu_cache_max_token_capacity"
 )
 
-func (p *Provider) refreshMetricsOnce() error {
-	start := time.Now()
-	defer func() {
-		d := time.Now().Sub(start)
-		// TODO: add a metric instead of logging
-		klog.V(4).Infof("Refreshed metrics in %v", d)
-	}()
-	var wg sync.WaitGroup
-	var errs error
-	processOnePod := func(key, value any) bool {
-		klog.V(4).Infof("Processing pod %v and metric %v", key, value)
-		pod := key.(Pod)
-		metrics := value.(*PodMetrics)
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-			metricFamilies, err := p.pmc.FetchMetrics(pod)
-			if err != nil {
-				multierr.Append(errs, fmt.Errorf("failed to parse metrics from %s: %v", pod, err))
-				return
-			}
-			updated, err := promToPodMetrics(metricFamilies, metrics)
-			klog.V(4).Infof("Updated metrics for pod %s: %v", pod, updated.Metrics)
-			if err != nil {
-				multierr.Append(errs, fmt.Errorf("failed to get all pod metrics updated from prometheus: %v", err))
-			}
-			p.UpdatePodMetrics(pod, updated)
-		}()
-		return true
+type PodMetricsClientImpl struct {
+}
+
+// FetchMetrics fetches metrics from a given pod.
+func (p *PodMetricsClientImpl) FetchMetrics(pod backend.Pod, existing *backend.PodMetrics) (*backend.PodMetrics, error) {
+	// Currently the metrics endpoint is hard-coded, which works with vLLM.
+	// TODO(https://github.com/kubernetes-sigs/llm-instance-gateway/issues/16): Consume this from LLMServerPool config.
+	url := fmt.Sprintf("http://%s/metrics", pod.Address)
+	resp, err := http.Get(url)
+	if err != nil {
+		klog.Errorf("failed to fetch metrics from %s: %v", pod, err)
+		return nil, fmt.Errorf("failed to fetch metrics from %s: %w", pod, err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		klog.Errorf("unexpected status code from %s: %v", pod, resp.StatusCode)
+		return nil, fmt.Errorf("unexpected status code from %s: %v", pod, resp.StatusCode)
+	}
+
+	parser := expfmt.TextParser{}
+	metricFamilies, err := parser.TextToMetricFamilies(resp.Body)
+	if err != nil {
+		return nil, err
 	}
-	p.podMetrics.Range(processOnePod)
-	wg.Wait()
-	return errs
+	return promToPodMetrics(metricFamilies, existing)
 }
 
 // promToPodMetrics updates internal pod metrics with scraped prometheus metrics.
 // A combined error is returned if errors occur in one or more metric processing.
 // it returns a new PodMetrics pointer which can be used to atomically update the pod metrics map.
-func promToPodMetrics(metricFamilies map[string]*dto.MetricFamily, existing *PodMetrics) (*PodMetrics, error) {
+func promToPodMetrics(metricFamilies map[string]*dto.MetricFamily, existing *backend.PodMetrics) (*backend.PodMetrics, error) {
 	var errs error
 	updated := existing.Clone()
 	runningQueueSize, _, err := getLatestMetric(metricFamilies, RunningQueueSizeMetricName)

pkg/ext-proc/benchmark/benchmark.go

@@ -12,7 +12,6 @@ import (
 	"github.com/bojand/ghz/runner"
 	extProcPb "github.com/envoyproxy/go-control-plane/envoy/service/ext_proc/v3"
 	"github.com/jhump/protoreflect/desc"
-	dto "github.com/prometheus/client_model/go"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/reflection"
 	"google.golang.org/protobuf/proto"
@@ -117,9 +116,9 @@ func startExtProc() {
 	s.Serve(lis)
 }
 
-func fakePods() (backend.PodSet, map[backend.Pod]map[string]*dto.MetricFamily) {
+func fakePods() (backend.PodSet, map[backend.Pod]*backend.PodMetrics) {
 	pods := make(backend.PodSet)
-	metrics := make(map[backend.Pod]map[string]*dto.MetricFamily, *numFakePods)
+	metrics := make(map[backend.Pod]*backend.PodMetrics, *numFakePods)
 	for i := 0; i < *numFakePods; i++ {
 		address := fmt.Sprintf("address-%v", i)
 		pod := backend.Pod{
@@ -135,78 +134,18 @@ func fakePods() (backend.PodSet, map[backend.Pod]map[string]*dto.MetricFamily) {
 }
 
 // fakeMetrics adds numModelsPerPod number of adapters to the pod metrics.
-func fakeMetrics(podNumber int) map[string]*dto.MetricFamily {
-	metrics := make(map[string]*dto.MetricFamily)
-	metrics["vllm:active_lora_adapters"] = &dto.MetricFamily{
-		Metric: []*dto.Metric{},
-	}
-	metrics["vllm:info_active_adapters_info"] = &dto.MetricFamily{
-		Metric: []*dto.Metric{
-			{
-				Label: []*dto.LabelPair{
-					{
-						Name:  ptrString("active_adapters"),
-						Value: ptrString(""),
-					},
-				},
-			},
+func fakeMetrics(podNumber int) *backend.PodMetrics {
+	metrics := &backend.PodMetrics{
+		Metrics: backend.Metrics{
+			CachedModels: make(map[string]int),
 		},
 	}
 	for i := 0; i < *numModelsPerPod; i++ {
-		mn := modelName(podNumber*(*numModelsPerPod) + i)
-		one := &dto.Metric{
-			Label: []*dto.LabelPair{
-				{
-					Name:  ptrString("active_lora_adapters"),
-					Value: ptrString(mn),
-				},
-			},
-			Gauge: &dto.Gauge{Value: ptrFloat64(0)},
-		}
-		metrics["vllm:active_lora_adapters"].Metric = append(metrics["vllm:active_lora_adapters"].Metric, one)
-
-		original := metrics["vllm:info_active_adapters_info"].Metric[0].Label[0].Value
-		metrics["vllm:info_active_adapters_info"].Metric[0].Label[0].Value = ptrString(*original + "," + mn)
-	}
-	metrics[backend.RunningQueueSizeMetricName] = &dto.MetricFamily{
-		Metric: []*dto.Metric{
-			{
-				Gauge: &dto.Gauge{Value: ptrFloat64(0)},
-			},
-		},
-	}
-	metrics[backend.WaitingQueueSizeMetricName] = &dto.MetricFamily{
-		Metric: []*dto.Metric{
-			{
-				Gauge: &dto.Gauge{Value: ptrFloat64(0)},
-			},
-		},
-	}
-	metrics[backend.KVCacheUsagePercentMetricName] = &dto.MetricFamily{
-		Metric: []*dto.Metric{
-			{
-				Gauge: &dto.Gauge{Value: ptrFloat64(0)},
-			},
-		},
-	}
-	metrics[backend.KvCacheMaxTokenCapacityMetricName] = &dto.MetricFamily{
-		Metric: []*dto.Metric{
-			{
-				Gauge: &dto.Gauge{Value: ptrFloat64(0)},
-			},
-		},
+		metrics.CachedModels[modelName(podNumber*(*numModelsPerPod)+i)] = 0
 	}
 	return metrics
 }
 
 func modelName(i int) string {
 	return fmt.Sprintf("adapter-%v", i)
 }
-
-func ptrString(s string) *string {
-	return &s
-}
-
-func ptrFloat64(f float64) *float64 {
-	return &f
-}

pkg/ext-proc/main.go

@@ -19,13 +19,11 @@ import (
 	klog "k8s.io/klog/v2"
 
 	"ext-proc/backend"
+	"ext-proc/backend/vllm"
 	"ext-proc/handlers"
 	"ext-proc/scheduling"
 )
 
-type extProcServer struct{}
-type server struct{}
-
 var (
 	port            = flag.Int("port", 9002, "gRPC port")
 	targetPodHeader = flag.String("targetPodHeader", "target-pod", "the header key for the target pod address to instruct Envoy to send the request to. This must match Envoy configuration.")
@@ -75,7 +73,7 @@ func main() {
 
 	s := grpc.NewServer()
 
-	pp := backend.NewProvider(&backend.PodMetricsClientImpl{}, &backend.FakePodLister{Pods: pods})
+	pp := backend.NewProvider(&vllm.PodMetricsClientImpl{}, &backend.FakePodLister{Pods: pods})
 	if err := pp.Init(*refreshPodsInterval, *refreshMetricsInterval); err != nil {
 		klog.Fatalf("failed to initialize: %v", err)
 	}