Do not warn on target allocator config load for non-TA Prometheus configs

plugins/inputs/prometheus/target_allocator.go

@@ -57,26 +57,30 @@ func isPodNameAvailable() bool {
 	}
 	return true
 }
-func loadConfigFromFilename(filename string) (*otelpromreceiver.Config, error) {
+
+// loadConfigFromFilename reads and parses the prometheus config file.
+// Returns the config, whether a target_allocator section was present, and any error.
+func loadConfigFromFilename(filename string) (*otelpromreceiver.Config, bool, error) {
 	yamlFile, err := os.ReadFile(filename)
 	if err != nil {
-		return nil, err
+		return nil, true, err // can't determine; default to warn
 	}
 	var stringMap map[string]interface{}
 	err = yaml.Unmarshal(yamlFile, &stringMap)
 	if err != nil {
-		return nil, err
+		return nil, true, err // can't determine; default to warn
 	}
+	_, hasTA := stringMap["target_allocator"]
 	componentParser := confmap.NewFromStringMap(stringMap)
 	if componentParser == nil {
-		return nil, fmt.Errorf("unable to parse config from filename %s", filename)
+		return nil, hasTA, fmt.Errorf("unable to parse config from filename %s", filename)
 	}
 	var cfg otelpromreceiver.Config
 	err = componentParser.Unmarshal(&cfg)
 	if err != nil {
-		return nil, err
+		return nil, hasTA, err
 	}
-	return &cfg, nil
+	return &cfg, hasTA, nil
 }
 
 func createTargetAllocatorManager(filename string, logger *slog.Logger, logLevel *promslog.AllowedLevel, sm *scrape.Manager, dm *discovery.Manager) *TargetAllocatorManager {
@@ -92,9 +96,13 @@ func createTargetAllocatorManager(filename string, logger *slog.Logger, logLevel
 		reloadConfigHandler: nil,
 		logger:              logger,
 	}
-	err := tam.loadConfig(filename)
+	hasTA, err := tam.loadConfig(filename)
 	if err != nil {
-		logger.Warn("Could not load config for target allocator from file", "filename", filename, "err", err)
+		if hasTA {
+			logger.Warn("Could not load config for target allocator from file", "filename", filename, "err", err)
+		} else {
+			logger.Debug("Target allocator not configured; skipping target allocator config load", "filename", filename, "err", err)
+		}
 		return &tam
 	}
 	if tam.config == nil {
@@ -142,21 +150,21 @@ func createZapLogger(level *promslog.AllowedLevel) (*zap.Logger, error) {
 	return zapLogger, err
 }
 
-func (tam *TargetAllocatorManager) loadConfig(filename string) error {
-	config, err := loadConfigFromFilename(filename)
+func (tam *TargetAllocatorManager) loadConfig(filename string) (bool, error) {
+	config, hasTA, err := loadConfigFromFilename(filename)
 	if err != nil {
-		return err
+		return hasTA, err
 	}
 	tam.config = config
 	if tam.config.TargetAllocator == nil {
-		return nil // no target allocator return
+		return hasTA, nil // no target allocator return
 	}
 	//has target allocator
 	tam.config.TargetAllocator.TLSSetting.CAFile = DefaultTLSCaFilePath
 	tam.config.TargetAllocator.TLSSetting.CertFile = DefaultTLSCertFilePath
 	tam.config.TargetAllocator.TLSSetting.KeyFile = DefaultTLSKeyFilePath
 	tam.config.TargetAllocator.TLSSetting.ReloadInterval = DEFAULT_TLS_RELOAD_INTERVAL_SECONDS
-	return nil
+	return hasTA, nil
 }
 func (tam *TargetAllocatorManager) Run() error {
 	err := tam.manager.Start(context.Background(), tam.host, tam.sm, tam.dm)

plugins/inputs/prometheus/target_allocator_test.go

@@ -0,0 +1,75 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: MIT
+
+package prometheus
+
+import (
+	"bytes"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/prometheus/common/promslog"
+	"github.com/stretchr/testify/assert"
+)
+
+// newCapturingLogger returns a logger that captures all output for test assertions.
+func newCapturingLogger() (*slog.Logger, *bytes.Buffer) {
+	buf := &bytes.Buffer{}
+	logger := slog.New(slog.NewTextHandler(buf, &slog.HandlerOptions{Level: slog.LevelDebug}))
+	return logger, buf
+}
+
+func infoLevel() *promslog.AllowedLevel {
+	lvl := &promslog.AllowedLevel{}
+	_ = lvl.Set("info")
+	return lvl
+}
+
+// TestCreateTargetAllocatorManager_NoTASection_NoWarn verifies no Warn is logged for a non-TA config.
+func TestCreateTargetAllocatorManager_NoTASection_NoWarn(t *testing.T) {
+	logger, buf := newCapturingLogger()
+
+	tam := createTargetAllocatorManager("testdata/base-k8.yaml", logger, infoLevel(), nil, nil)
+
+	assert.False(t, tam.enabled, "TA must be disabled")
+
+	out := buf.String()
+	assert.NotContains(t, out, "level=WARN", "no Warn expected")
+	assert.NotContains(t, out, "Could not load config for target allocator",
+		"spurious TA warning must not appear")
+
+	assert.Contains(t, out, "level=DEBUG")
+	assert.Contains(t, out, "Target allocator not configured")
+}
+
+// TestCreateTargetAllocatorManager_MalformedTASection_Warns verifies a genuine TA config error still warns.
+func TestCreateTargetAllocatorManager_MalformedTASection_Warns(t *testing.T) {
+	dir := t.TempDir()
+	badTA := filepath.Join(dir, "bad-ta.yaml")
+	// Has target_allocator section but an invalid key that fails strict unmarshal.
+	content := []byte("target_allocator:\n  endpoint: http://target-allocator-service:80\n  interval: 30s\nthis_key_is_invalid: true\n")
+	assert.NoError(t, os.WriteFile(badTA, content, 0o600))
+
+	logger, buf := newCapturingLogger()
+
+	tam := createTargetAllocatorManager(badTA, logger, infoLevel(), nil, nil)
+
+	assert.False(t, tam.enabled, "manager stays disabled")
+	out := buf.String()
+	assert.Contains(t, out, "level=WARN", "genuine TA error must still warn")
+	assert.Contains(t, out, "Could not load config for target allocator")
+}
+
+// TestLoadConfigFromFilename_HasTA tests the TA section detection in loadConfigFromFilename.
+func TestLoadConfigFromFilename_HasTA(t *testing.T) {
+	_, hasTA, _ := loadConfigFromFilename("testdata/base-k8.yaml")
+	assert.False(t, hasTA, "no TA section")
+
+	_, hasTA, _ = loadConfigFromFilename("testdata/target_allocator.yaml")
+	assert.True(t, hasTA, "has TA section")
+
+	_, hasTA, _ = loadConfigFromFilename("testdata/does-not-exist.yaml")
+	assert.True(t, hasTA, "missing file defaults to true (warn)")
+}