update algorithm parameters from env variables (#580)

* update algorithm parameters form env variables

* move env parsers to a new pkg in utils

* add unit test for env parser

* remove logging env variables during scheduling

* add test for env parser

Author: kaushikmitr

Diff for: pkg/epp/scheduling/filter.go

@@ -141,7 +141,7 @@ func leastQueuingFilterFunc(logger logr.Logger, req *LLMRequest, pods []backendm
 }
 
 func lowQueueingPodPredicate(_ *LLMRequest, pod backendmetrics.PodMetrics) bool {
-	return pod.GetMetrics().WaitingQueueSize < queueingThresholdLoRA
+	return pod.GetMetrics().WaitingQueueSize < config.QueueingThresholdLoRA
 }
 
 // leastKVCacheFilterFunc finds the max and min KV cache of all pods, divides the whole range
@@ -223,7 +223,7 @@ func loRASoftAffinityFilter(logger logr.Logger, req *LLMRequest, pods []backendm
 
 	// If both groups have pods, use probability to select which group to return
 	if len(filtered_affinity) > 0 && len(filtered_available) > 0 {
-		if randGen.Float64() < loraAffinityThreshold {
+		if randGen.Float64() < config.LoraAffinityThreshold {
 			return filtered_affinity, nil
 		}
 		return filtered_available, nil

Diff for: pkg/epp/scheduling/filter_test.go

@@ -442,6 +442,18 @@ func TestLoRASoftAffinityDistribution(t *testing.T) {
 		tolerancePercent  = 5.0 // Allow 5% tolerance from expected distribution
 	)
 
+	// Save original config value to restore later
+	originalThreshold := config.LoraAffinityThreshold
+
+	// Set a specific test value for this test
+	testThreshold := 0.75 // 75%
+	config.LoraAffinityThreshold = testThreshold
+
+	// Ensure we restore the original threshold when test completes
+	defer func() {
+		config.LoraAffinityThreshold = originalThreshold
+	}()
+
 	// Create a test request and pods
 	req := &LLMRequest{
 		Model:               testAffinityModel,
@@ -472,9 +484,10 @@ func TestLoRASoftAffinityDistribution(t *testing.T) {
 	affinityCount := 0
 	availableCount := 0
 
-	// Use the actual loraAffinityThreshold as defined in the original code
-	// This test should work with whatever value is set there
-	expectedAffinityPercent := loraAffinityThreshold * 100
+	// Use the test threshold value
+	expectedAffinityPercent := config.LoraAffinityThreshold * 100
+	expectedAvailabilityPercent := 100 - expectedAffinityPercent
+
 	for i := 0; i < numIterations; i++ {
 		result, err := loRASoftAffinityFilter(logger, req, toInterface(pods))
 		if err != nil {
@@ -502,11 +515,12 @@ func TestLoRASoftAffinityDistribution(t *testing.T) {
 	affinityLowerBound := expectedAffinityPercent - tolerancePercent
 	affinityUpperBound := expectedAffinityPercent + tolerancePercent
 
-	availableLowerBound := actualAvailablePercent - tolerancePercent
-	availableUpperBound := actualAvailablePercent + tolerancePercent
+	availableLowerBound := expectedAvailabilityPercent - tolerancePercent
+	availableUpperBound := expectedAvailabilityPercent + tolerancePercent
 
 	t.Logf("Distribution results over %d iterations:", numIterations)
-	t.Logf("Expected affinity percent: %.2f%% (threshold: %.2f)", expectedAffinityPercent, loraAffinityThreshold)
+	t.Logf("Expected affinity percent: %.2f%% (threshold: %.2f)", expectedAffinityPercent, config.LoraAffinityThreshold)
+	t.Logf("Expected availability percent: %.2f%% (threshold: %.2f)", expectedAvailabilityPercent, config.LoraAffinityThreshold)
 	t.Logf("Actual affinity percent: %.2f%% (%d out of %d)", actualAffinityPercent, affinityCount, numIterations)
 	t.Logf("Actual available percent: %.2f%% (%d out of %d)", actualAvailablePercent, availableCount, numIterations)
 

Diff for: pkg/epp/scheduling/scheduler.go

@@ -26,24 +26,46 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/log"
 	backendmetrics "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/backend/metrics"
 	"sigs.k8s.io/gateway-api-inference-extension/pkg/epp/datastore"
+	envutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/env"
 	errutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/error"
 	logutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/logging"
 )
 
+// Config holds all the configuration values for the scheduler
+type Config struct {
+	KVCacheThreshold       float64
+	QueueThresholdCritical int
+	QueueingThresholdLoRA  int
+	LoraAffinityThreshold  float64
+}
+
 const (
-	// TODO(https://github.com/kubernetes-sigs/gateway-api-inference-extension/issues/16) Make this configurable.
-	kvCacheThreshold = 0.8
-	// TODO(https://github.com/kubernetes-sigs/gateway-api-inference-extension/issues/16) Make this configurable.
-	queueThresholdCritical = 5
-	// TODO(https://github.com/kubernetes-sigs/gateway-api-inference-extension/issues/16) Make this configurable.
-	// the threshold for queued requests to be considered low below which we can prioritize LoRA affinity.
-	// The value of 128 is arrived heuristicically based on experiments.
-	queueingThresholdLoRA = 128
-	// TODO(https://github.com/kubernetes-sigs/gateway-api-inference-extension/issues/16) Make this configurable.
-	// loraAffinityThreshold indicates the probability with which we prefer a pod with LoRA affinity over a pod without but having room to fit more LoRA adapters.
-	loraAffinityThreshold = 0.999
+	// Default values to use if environment variables are not set
+	defaultKVCacheThreshold       = 0.8
+	defaultQueueThresholdCritical = 5
+	defaultQueueingThresholdLoRA  = 128
+	defaultLoraAffinityThreshold  = 0.999
 )
 
+// LoadConfig loads configuration from environment variables
+func LoadConfig() Config {
+	// Use a default logger for initial configuration loading
+	baseLogger := log.Log.WithName("scheduling-config")
+
+	config := Config{
+		KVCacheThreshold:       envutil.GetEnvFloat("KV_CACHE_THRESHOLD", defaultKVCacheThreshold, baseLogger),
+		QueueThresholdCritical: envutil.GetEnvInt("QUEUE_THRESHOLD_CRITICAL", defaultQueueThresholdCritical, baseLogger),
+		QueueingThresholdLoRA:  envutil.GetEnvInt("QUEUING_THRESHOLD_LORA", defaultQueueingThresholdLoRA, baseLogger),
+		LoraAffinityThreshold:  envutil.GetEnvFloat("LORA_AFFINITY_THRESHOLD", defaultLoraAffinityThreshold, baseLogger),
+	}
+
+	baseLogger.V(logutil.DEFAULT).Info("Scheduler configuration loaded", "config", config)
+
+	return config
+}
+
+var config = LoadConfig()
+
 var (
 	defaultFilter = &filter{
 		name:          "critical request",
@@ -92,7 +114,7 @@ var (
 		// cache below a certain threshold, we consider this model server has capacity to handle
 		// a sheddable request without impacting critical requests.
 		name:          "has capacity for sheddable requests",
-		filter:        toFilterFunc(noQueueAndLessThanKVCacheThresholdPredicate(queueThresholdCritical, kvCacheThreshold)),
+		filter:        toFilterFunc(noQueueAndLessThanKVCacheThresholdPredicate(config.QueueThresholdCritical, config.KVCacheThreshold)),
 		nextOnSuccess: queueLoRAAndKVCacheFilter,
 		// If all pods are queuing or running above the KVCache threshold, we drop the sheddable
 		// request to make room for critical requests.
@@ -123,13 +145,13 @@ type Scheduler struct {
 // Schedule finds the target pod based on metrics and the requested lora adapter.
 func (s *Scheduler) Schedule(ctx context.Context, req *LLMRequest) (targetPod backendmetrics.PodMetrics, err error) {
 	logger := log.FromContext(ctx).WithValues("request", req)
-	podMetrics := s.datastore.PodGetAll()
 
+	podMetrics := s.datastore.PodGetAll()
 	logger.V(logutil.DEBUG).Info(fmt.Sprintf("Scheduling a request. Metrics: %+v", podMetrics))
+
 	pods, err := s.filter.Filter(logger, req, podMetrics)
 	if err != nil || len(pods) == 0 {
-		return nil, fmt.Errorf(
-			"failed to apply filter, resulted %v pods, this should never happen: %w", len(pods), err)
+		return nil, fmt.Errorf("failed to apply filter, resulted %v pods, this should never happen: %w", len(pods), err)
 	}
 	logger.V(logutil.DEBUG).Info(fmt.Sprintf("Selecting a random pod from %d candidates: %+v", len(pods), pods))
 	i := rand.Intn(len(pods))

Diff for: pkg/epp/util/env/env.go

@@ -0,0 +1,51 @@
+package env
+
+import (
+	"os"
+	"strconv"
+
+	"github.com/go-logr/logr"
+	logutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/logging"
+)
+
+// getEnvFloat gets a float64 from an environment variable with a default value
+func GetEnvFloat(key string, defaultVal float64, logger logr.Logger) float64 {
+	val, exists := os.LookupEnv(key)
+	if !exists {
+		logger.V(logutil.VERBOSE).Info("Environment variable not set, using default value",
+			"key", key, "defaultValue", defaultVal)
+		return defaultVal
+	}
+
+	floatVal, err := strconv.ParseFloat(val, 64)
+	if err != nil {
+		logger.V(logutil.VERBOSE).Info("Failed to parse environment variable as float, using default value",
+			"key", key, "value", val, "error", err, "defaultValue", defaultVal)
+		return defaultVal
+	}
+
+	logger.V(logutil.VERBOSE).Info("Successfully loaded environment variable",
+		"key", key, "value", floatVal)
+	return floatVal
+}
+
+// getEnvInt gets an int from an environment variable with a default value
+func GetEnvInt(key string, defaultVal int, logger logr.Logger) int {
+	val, exists := os.LookupEnv(key)
+	if !exists {
+		logger.V(logutil.VERBOSE).Info("Environment variable not set, using default value",
+			"key", key, "defaultValue", defaultVal)
+		return defaultVal
+	}
+
+	intVal, err := strconv.Atoi(val)
+	if err != nil {
+		logger.V(logutil.VERBOSE).Info("Failed to parse environment variable as int, using default value",
+			"key", key, "value", val, "error", err, "defaultValue", defaultVal)
+		return defaultVal
+	}
+
+	logger.V(logutil.VERBOSE).Info("Successfully loaded environment variable",
+		"key", key, "value", intVal)
+	return intVal
+}

Diff for: pkg/epp/util/env/env_test.go

@@ -0,0 +1,144 @@
+package env
+
+import (
+	"os"
+	"testing"
+
+	"github.com/go-logr/logr/testr"
+	logutil "sigs.k8s.io/gateway-api-inference-extension/pkg/epp/util/logging"
+)
+
+func TestGetEnvFloat(t *testing.T) {
+	logger := testr.New(t)
+
+	tests := []struct {
+		name       string
+		key        string
+		value      string
+		defaultVal float64
+		expected   float64
+		setup      func()
+		teardown   func()
+	}{
+		{
+			name:       "env variable exists and is valid",
+			key:        "TEST_FLOAT",
+			value:      "123.456",
+			defaultVal: 0.0,
+			expected:   123.456,
+			setup: func() {
+				os.Setenv("TEST_FLOAT", "123.456")
+			},
+			teardown: func() {
+				os.Unsetenv("TEST_FLOAT")
+			},
+		},
+		{
+			name:       "env variable exists but is invalid",
+			key:        "TEST_FLOAT",
+			value:      "invalid",
+			defaultVal: 99.9,
+			expected:   99.9,
+			setup: func() {
+				os.Setenv("TEST_FLOAT", "invalid")
+			},
+			teardown: func() {
+				os.Unsetenv("TEST_FLOAT")
+			},
+		},
+		{
+			name:       "env variable does not exist",
+			key:        "TEST_FLOAT_MISSING",
+			defaultVal: 42.42,
+			expected:   42.42,
+			setup:      func() {},
+			teardown:   func() {},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			tc.setup()
+			defer tc.teardown()
+
+			result := GetEnvFloat(tc.key, tc.defaultVal, logger.V(logutil.VERBOSE))
+			if result != tc.expected {
+				t.Errorf("GetEnvFloat(%s, %f) = %f, expected %f", tc.key, tc.defaultVal, result, tc.expected)
+			}
+		})
+	}
+}
+
+func TestGetEnvInt(t *testing.T) {
+	logger := testr.New(t)
+
+	tests := []struct {
+		name       string
+		key        string
+		value      string
+		defaultVal int
+		expected   int
+		setup      func()
+		teardown   func()
+	}{
+		{
+			name:       "env variable exists and is valid",
+			key:        "TEST_INT",
+			value:      "123",
+			defaultVal: 0,
+			expected:   123,
+			setup: func() {
+				os.Setenv("TEST_INT", "123")
+			},
+			teardown: func() {
+				os.Unsetenv("TEST_INT")
+			},
+		},
+		{
+			name:       "env variable exists but is invalid",
+			key:        "TEST_INT",
+			value:      "invalid",
+			defaultVal: 99,
+			expected:   99,
+			setup: func() {
+				os.Setenv("TEST_INT", "invalid")
+			},
+			teardown: func() {
+				os.Unsetenv("TEST_INT")
+			},
+		},
+		{
+			name:       "env variable does not exist",
+			key:        "TEST_INT_MISSING",
+			defaultVal: 42,
+			expected:   42,
+			setup:      func() {},
+			teardown:   func() {},
+		},
+		{
+			name:       "env variable is empty string",
+			key:        "TEST_INT_EMPTY",
+			value:      "",
+			defaultVal: 77,
+			expected:   77,
+			setup: func() {
+				os.Setenv("TEST_INT_EMPTY", "")
+			},
+			teardown: func() {
+				os.Unsetenv("TEST_INT_EMPTY")
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			tc.setup()
+			defer tc.teardown()
+
+			result := GetEnvInt(tc.key, tc.defaultVal, logger.V(logutil.VERBOSE))
+			if result != tc.expected {
+				t.Errorf("GetEnvInt(%s, %d) = %d, expected %d", tc.key, tc.defaultVal, result, tc.expected)
+			}
+		})
+	}
+}