feat: add pdrole package for P/D role discovery and detection

internal/utils/pdrole/detect.go

@@ -0,0 +1,63 @@
+package pdrole
+
+import (
+	appsv1 "k8s.io/api/apps/v1"
+)
+
+// GetDeploymentPDRole determines the P/D role of a deployment by checking
+// pod template labels against the provided labelConfig.
+//
+// This is label-only detection, matching how the EPP's filter plugins work:
+// the EPP's prefill-filter and decode-filter (and by-label) plugins route
+// traffic based solely on pod labels, never deployment names.
+//
+// Returns RoleUnknown if the deployment has no matching label. Callers should
+// use the PDDiscoveryResult.Disaggregated flag to interpret RoleUnknown:
+//   - If Disaggregated=false, skip detection entirely and treat all deployments as RoleBoth
+//   - If Disaggregated=true and RoleUnknown, the deployment has no P/D label set
+func GetDeploymentPDRole(deploy *appsv1.Deployment, labelConfig PDRoleLabelConfig) PDRole {
+	if deploy == nil {
+		return RoleUnknown
+	}
+
+	return detectFromLabels(deploy, labelConfig)
+}
+
+// detectFromLabels checks pod template labels against the label config.
+func detectFromLabels(deploy *appsv1.Deployment, config PDRoleLabelConfig) PDRole {
+	if config.LabelKey == "" {
+		return RoleUnknown
+	}
+
+	labels := deploy.Spec.Template.Labels
+	if labels == nil {
+		return RoleUnknown
+	}
+
+	value, exists := labels[config.LabelKey]
+	if !exists {
+		return RoleUnknown
+	}
+
+	return matchLabelValue(value, config)
+}
+
+// matchLabelValue matches a label value against the config's role value lists.
+func matchLabelValue(value string, config PDRoleLabelConfig) PDRole {
+	for _, v := range config.PrefillValues {
+		if value == v {
+			return RolePrefill
+		}
+	}
+	for _, v := range config.DecodeValues {
+		if value == v {
+			return RoleDecode
+		}
+	}
+	for _, v := range config.BothValues {
+		if value == v {
+			return RoleBoth
+		}
+	}
+	return RoleUnknown
+}

internal/utils/pdrole/detect_test.go

@@ -0,0 +1,130 @@
+package pdrole
+
+import (
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+
+	appsv1 "k8s.io/api/apps/v1"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func makeDeployment(name string, labels map[string]string) *appsv1.Deployment {
+	return &appsv1.Deployment{
+		ObjectMeta: metav1.ObjectMeta{Name: name, Namespace: "default"},
+		Spec: appsv1.DeploymentSpec{
+			Template: corev1.PodTemplateSpec{
+				ObjectMeta: metav1.ObjectMeta{Labels: labels},
+			},
+		},
+	}
+}
+
+var _ = Describe("GetDeploymentPDRole", func() {
+	var defaultConfig PDRoleLabelConfig
+
+	BeforeEach(func() {
+		defaultConfig = DefaultPDRoleLabelConfig()
+	})
+
+	Context("with nil deployment", func() {
+		It("should return RoleUnknown", func() {
+			Expect(GetDeploymentPDRole(nil, defaultConfig)).To(Equal(RoleUnknown))
+		})
+	})
+
+	Context("with label-based detection", func() {
+		It("should detect prefill from label", func() {
+			deploy := makeDeployment("vllm-llama", map[string]string{DefaultRoleLabel: "prefill"})
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RolePrefill))
+		})
+
+		It("should detect decode from label", func() {
+			deploy := makeDeployment("vllm-llama", map[string]string{DefaultRoleLabel: "decode"})
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RoleDecode))
+		})
+
+		It("should detect both from label", func() {
+			deploy := makeDeployment("vllm-llama", map[string]string{DefaultRoleLabel: "both"})
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RoleBoth))
+		})
+
+		It("should return unknown for unrecognized label value", func() {
+			deploy := makeDeployment("vllm-llama", map[string]string{DefaultRoleLabel: "invalid"})
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RoleUnknown))
+		})
+	})
+
+	Context("without P/D label", func() {
+		It("should return unknown even if name contains prefill", func() {
+			deploy := makeDeployment("llama-prefill-a100", map[string]string{"app": "vllm"})
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RoleUnknown))
+		})
+
+		It("should return unknown even if name contains decode", func() {
+			deploy := makeDeployment("llama-decode-h100", map[string]string{"app": "vllm"})
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RoleUnknown))
+		})
+
+		It("should return unknown with no labels at all", func() {
+			deploy := makeDeployment("llama-prefill", nil)
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RoleUnknown))
+		})
+
+		It("should return unknown with generic name and no P/D label", func() {
+			deploy := makeDeployment("vllm-llama", map[string]string{"app": "vllm"})
+			Expect(GetDeploymentPDRole(deploy, defaultConfig)).To(Equal(RoleUnknown))
+		})
+	})
+
+	Context("with custom label config", func() {
+		It("should detect prefill with custom label key and values", func() {
+			config := PDRoleLabelConfig{
+				LabelKey:      "my.org/pd-role",
+				PrefillValues: []string{"p"},
+				DecodeValues:  []string{"d"},
+				BothValues:    []string{"pd"},
+			}
+			deploy := makeDeployment("vllm-llama", map[string]string{"my.org/pd-role": "p"})
+			Expect(GetDeploymentPDRole(deploy, config)).To(Equal(RolePrefill))
+		})
+
+		It("should detect decode with custom label key and values", func() {
+			config := PDRoleLabelConfig{
+				LabelKey:      "my.org/pd-role",
+				PrefillValues: []string{"p"},
+				DecodeValues:  []string{"d"},
+				BothValues:    []string{"pd"},
+			}
+			deploy := makeDeployment("vllm-llama", map[string]string{"my.org/pd-role": "d"})
+			Expect(GetDeploymentPDRole(deploy, config)).To(Equal(RoleDecode))
+		})
+
+		It("should detect both with custom label key and values", func() {
+			config := PDRoleLabelConfig{
+				LabelKey:      "my.org/pd-role",
+				PrefillValues: []string{"p"},
+				DecodeValues:  []string{"d"},
+				BothValues:    []string{"pd"},
+			}
+			deploy := makeDeployment("vllm-llama", map[string]string{"my.org/pd-role": "pd"})
+			Expect(GetDeploymentPDRole(deploy, config)).To(Equal(RoleBoth))
+		})
+
+		It("should return unknown when label key is empty", func() {
+			config := PDRoleLabelConfig{LabelKey: ""}
+			deploy := makeDeployment("vllm-llama", map[string]string{DefaultRoleLabel: "prefill"})
+			Expect(GetDeploymentPDRole(deploy, config)).To(Equal(RoleUnknown))
+		})
+	})
+})
+
+var _ = Describe("DefaultPDRoleLabelConfig", func() {
+	It("should return standard configuration", func() {
+		config := DefaultPDRoleLabelConfig()
+		Expect(config.LabelKey).To(Equal(DefaultRoleLabel))
+		Expect(config.PrefillValues).To(Equal([]string{"prefill"}))
+		Expect(config.DecodeValues).To(Equal([]string{"decode"}))
+		Expect(config.BothValues).To(Equal([]string{"both"}))
+	})
+})