Replace Viper with encoding/json for config loading (#143)

Author: wenxuan0923

go.mod

@@ -17,7 +17,6 @@ require (
 	github.com/schollz/progressbar/v3 v3.19.0
 	github.com/sirupsen/logrus v1.9.3
 	github.com/spf13/cobra v1.10.1
-	github.com/spf13/viper v1.21.0
 	golang.org/x/sync v0.19.0
 	google.golang.org/grpc v1.72.3
 	google.golang.org/protobuf v1.36.8
@@ -49,14 +48,12 @@ require (
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/emicklei/go-restful/v3 v3.13.0 // indirect
 	github.com/exponent-io/jsonpath v0.0.0-20210407135951-1de76d718b3f // indirect
-	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/fxamacker/cbor/v2 v2.9.0 // indirect
 	github.com/go-errors/errors v1.4.2 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-openapi/jsonpointer v0.21.0 // indirect
 	github.com/go-openapi/jsonreference v0.20.2 // indirect
 	github.com/go-openapi/swag v0.23.0 // indirect
-	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
 	github.com/godbus/dbus/v5 v5.0.4 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang-jwt/jwt/v4 v4.5.2 // indirect
@@ -78,7 +75,6 @@ require (
 	github.com/modern-go/reflect2 v1.0.3-0.20250322232337-35a7c28c31ee // indirect
 	github.com/monochromegane/go-gitignore v0.0.0-20200626010858-205db1a8cc00 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
-	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
 	github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
 	github.com/pkg/browser v0.0.0-20240102092130-5ac0b6a4141c // indirect
 	github.com/pkg/errors v0.9.1 // indirect
@@ -88,12 +84,7 @@ require (
 	github.com/prometheus/procfs v0.16.1 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
-	github.com/sagikazarmark/locafero v0.11.0 // indirect
-	github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 // indirect
-	github.com/spf13/afero v1.15.0 // indirect
-	github.com/spf13/cast v1.10.0 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect
-	github.com/subosito/gotenv v1.6.0 // indirect
 	github.com/x448/float16 v0.8.4 // indirect
 	github.com/xlab/treeprint v1.2.0 // indirect
 	go.opentelemetry.io/otel v1.36.0 // indirect

go.sum

@@ -70,10 +70,6 @@ github.com/emicklei/go-restful/v3 v3.13.0 h1:C4Bl2xDndpU6nJ4bc1jXd+uTmYPVUwkD6bF
 github.com/emicklei/go-restful/v3 v3.13.0/go.mod h1:6n3XBCmQQb25CM2LCACGz8ukIrRry+4bhvbpWn3mrbc=
 github.com/exponent-io/jsonpath v0.0.0-20210407135951-1de76d718b3f h1:Wl78ApPPB2Wvf/TIe2xdyJxTlb6obmF18d8QdkxNDu4=
 github.com/exponent-io/jsonpath v0.0.0-20210407135951-1de76d718b3f/go.mod h1:OSYXu++VVOHnXeitef/D8n/6y4QV8uLHSFXX4NeXMGc=
-github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
-github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
-github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
-github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/fxamacker/cbor/v2 v2.9.0 h1:NpKPmjDBgUfBms6tr6JZkTHtfFGcMKsw3eGcmD/sapM=
 github.com/fxamacker/cbor/v2 v2.9.0/go.mod h1:vM4b+DJCtHn+zz7h3FFp/hDAI9WNWCsZj23V5ytsSxQ=
 github.com/go-errors/errors v1.4.2 h1:J6MZopCL4uSllY1OfXM374weqZFFItUbrImctkmUxIA=
@@ -92,8 +88,6 @@ github.com/go-openapi/swag v0.23.0 h1:vsEVJDUo2hPJ2tu0/Xc+4noaxyEffXNIs3cOULZ+Gr
 github.com/go-openapi/swag v0.23.0/go.mod h1:esZ8ITTYEsH1V2trKHjAN8Ai7xHb8RV+YSZ577vPjgQ=
 github.com/go-task/slim-sprig/v3 v3.0.0 h1:sUs3vkvUymDpBKi3qH1YSqBQk9+9D/8M2mN1vB6EwHI=
 github.com/go-task/slim-sprig/v3 v3.0.0/go.mod h1:W848ghGpv3Qj3dhTPRyJypKRiqCdHZiAzKg9hl15HA8=
-github.com/go-viper/mapstructure/v2 v2.4.0 h1:EBsztssimR/CONLSZZ04E8qAkxNYq4Qp9LvH92wZUgs=
-github.com/go-viper/mapstructure/v2 v2.4.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/godbus/dbus/v5 v5.0.4 h1:9349emZab16e7zQvpmsbtjc18ykshndd8y2PG3sgJbA=
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/gogo/protobuf v1.3.2 h1:Ov1cvc58UF3b5XjBnZv7+opcTcQFZebYjWzi34vdm4Q=
@@ -168,8 +162,6 @@ github.com/onsi/ginkgo/v2 v2.27.2 h1:LzwLj0b89qtIy6SSASkzlNvX6WktqurSHwkk2ipF/Ns
 github.com/onsi/ginkgo/v2 v2.27.2/go.mod h1:ArE1D/XhNXBXCBkKOLkbsb2c81dQHCRcF5zwn/ykDRo=
 github.com/onsi/gomega v1.38.2 h1:eZCjf2xjZAqe+LeWvKb5weQ+NcPwX84kqJ0cZNxok2A=
 github.com/onsi/gomega v1.38.2/go.mod h1:W2MJcYxRGV63b418Ai34Ud0hEdTVXq9NW9+Sx6uXf3k=
-github.com/pelletier/go-toml/v2 v2.2.4 h1:mye9XuhQ6gvn5h28+VilKrrPoQVanw5PMw/TB0t5Ec4=
-github.com/pelletier/go-toml/v2 v2.2.4/go.mod h1:2gIqNv+qfxSVS7cM2xJQKtLSTLUE9V8t9Stt+h56mCY=
 github.com/peterbourgon/diskv v2.0.1+incompatible h1:UBdAOUP5p4RWqPBg048CAvpKN+vxiaj6gdUUzhl4XmI=
 github.com/peterbourgon/diskv v2.0.1+incompatible/go.mod h1:uqqh8zWWbv1HBMNONnaR/tNboyR3/BZd58JJSHlUSCU=
 github.com/pkg/browser v0.0.0-20240102092130-5ac0b6a4141c h1:+mdjkGKdHQG3305AYmdv1U2eRNDiU2ErMBj1gwrq8eQ=
@@ -192,27 +184,17 @@ github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0t
 github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
 github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
-github.com/sagikazarmark/locafero v0.11.0 h1:1iurJgmM9G3PA/I+wWYIOw/5SyBtxapeHDcg+AAIFXc=
-github.com/sagikazarmark/locafero v0.11.0/go.mod h1:nVIGvgyzw595SUSUE6tvCp3YYTeHs15MvlmU87WwIik=
 github.com/schollz/progressbar/v3 v3.19.0 h1:Ea18xuIRQXLAUidVDox3AbwfUhD0/1IvohyTutOIFoc=
 github.com/schollz/progressbar/v3 v3.19.0/go.mod h1:IsO3lpbaGuzh8zIMzgY3+J8l4C8GjO0Y9S69eFvNsec=
 github.com/sergi/go-diff v1.2.0 h1:XU+rvMAioB0UC3q1MFrIQy4Vo5/4VsRDQQXHsEya6xQ=
 github.com/sergi/go-diff v1.2.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
 github.com/sirupsen/logrus v1.9.3 h1:dueUQJ1C2q9oE3F7wvmSGAaVtTmUizReu6fjN8uqzbQ=
 github.com/sirupsen/logrus v1.9.3/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
-github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 h1:+jumHNA0Wrelhe64i8F6HNlS8pkoyMv5sreGx2Ry5Rw=
-github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8/go.mod h1:3n1Cwaq1E1/1lhQhtRK2ts/ZwZEhjcQeJQ1RuC6Q/8U=
-github.com/spf13/afero v1.15.0 h1:b/YBCLWAJdFWJTN9cLhiXXcD7mzKn9Dm86dNnfyQw1I=
-github.com/spf13/afero v1.15.0/go.mod h1:NC2ByUVxtQs4b3sIUphxK0NioZnmxgyCrfzeuq8lxMg=
-github.com/spf13/cast v1.10.0 h1:h2x0u2shc1QuLHfxi+cTJvs30+ZAHOGRic8uyGTDWxY=
-github.com/spf13/cast v1.10.0/go.mod h1:jNfB8QC9IA6ZuY2ZjDp0KtFO2LZZlg4S/7bzP6qqeHo=
 github.com/spf13/cobra v1.10.1 h1:lJeBwCfmrnXthfAupyUTzJ/J4Nc1RsHC/mSRU2dll/s=
 github.com/spf13/cobra v1.10.1/go.mod h1:7SmJGaTHFVBY0jW4NXGluQoLvhqFQM+6XSKD+P4XaB0=
 github.com/spf13/pflag v1.0.9/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
 github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
-github.com/spf13/viper v1.21.0 h1:x5S+0EU27Lbphp4UKm1C+1oQO+rKx36vfCoaVebLFSU=
-github.com/spf13/viper v1.21.0/go.mod h1:P0lhsswPGWD/1lZJ9ny3fYnVqxiegrlNrEmgLjbTCAY=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
@@ -227,8 +209,6 @@ github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o
 github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
-github.com/subosito/gotenv v1.6.0 h1:9NlTDc1FTs4qu0DDq7AEtTPNw6SVm7uBMsUCUjABIf8=
-github.com/subosito/gotenv v1.6.0/go.mod h1:Dk4QP5c2W3ibzajGcXpNraDfq2IrhjMIvMSWPKKo0FU=
 github.com/x448/float16 v0.8.4 h1:qLwI1I70+NjRFUR3zs1JPUCgaCXSh3SW62uAKT1mSBM=
 github.com/x448/float16 v0.8.4/go.mod h1:14CWIYCyZA/cWjXOioeEpHeN/83MdbZDRQHoFcYsOfg=
 github.com/xlab/treeprint v1.2.0 h1:HzHnuAF1plUN2zGlAFHbSQP2qJ0ZAD3XF5XD7OesXRQ=

pkg/config/config.go

@@ -1,11 +1,12 @@
 package config
 
 import (
+	"encoding/json"
 	"fmt"
+	"os"
+	"path/filepath"
 	"regexp"
 	"sync"
-
-	"github.com/spf13/viper"
 )
 
 const (
@@ -18,9 +19,6 @@ const (
 	defaultLogDir     = "/var/log/aks-flex-node"
 	defaultLogLevel   = "info"
 	defaultAzureCloud = "AzurePublicCloud"
-
-	// Environment variable prefix
-	envPrefix = "AKS_NODE_CONTROLLER"
 )
 
 // Singleton instance for configuration
@@ -38,38 +36,27 @@ func GetConfig() *Config {
 	return configInstance
 }
 
-// LoadConfig loads configuration from a JSON file and environment variables.
+// LoadConfig loads configuration from a JSON file.
 // The configPath parameter is required and cannot be empty.
-// Environment variables can override config file values using the AKS_NODE_CONTROLLER_ prefix.
-// For example: AKS_NODE_CONTROLLER_AZURE_LOCATION=westus2
 func LoadConfig(configPath string) (*Config, error) {
 	// Require config path to be specified
 	if configPath == "" {
 		return nil, fmt.Errorf("config file path is required")
 	}
 
-	// Set up viper
-	v := viper.New()
-	v.SetConfigType("json")
-	v.AutomaticEnv()
-	v.SetEnvPrefix(envPrefix)
-
-	// Load the specified config file
-	v.SetConfigFile(configPath)
-	if err := v.ReadInConfig(); err != nil {
+	data, err := os.ReadFile(filepath.Clean(configPath))
+	if err != nil {
 		return nil, fmt.Errorf("failed to read config file at %s: %w", configPath, err)
 	}
 
-	// Unmarshal config
 	config := &Config{}
-	if err := v.Unmarshal(config); err != nil {
+	if err := json.Unmarshal(data, config); err != nil {
 		return nil, fmt.Errorf("error unmarshaling config: %w", err)
 	}
 
-	// Track if managedIdentity was explicitly set in config
-	// This is necessary because viper unmarshals empty JSON objects {} as nil pointers
-	// Using viper.IsSet() correctly detects if the key was present in the config file
-	config.isMIExplicitlySet = v.IsSet("azure.managedIdentity")
+	// encoding/json deserializes "managedIdentity": {} into a non-nil pointer, so
+	// presence can be detected directly — unlike Viper which decoded it as nil.
+	config.isMIExplicitlySet = config.Azure.ManagedIdentity != nil
 
 	// Set defaults for any missing values
 	config.SetDefaults()

pkg/config/config_test.go

@@ -1,8 +1,10 @@
 package config
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"testing"
 )
@@ -1069,6 +1071,128 @@ func TestAuthenticationMethodValidation(t *testing.T) {
 	}
 }
 
+// baseAzureJSON is the minimal valid azure config block shared across label tests.
+const baseAzureJSON = `{
+	"azure": {
+		"subscriptionId": "12345678-1234-1234-1234-123456789012",
+		"tenantId": "12345678-1234-1234-1234-123456789012",
+		"cloud": "AzurePublicCloud",
+		"bootstrapToken": { "token": "abcdef.0123456789abcdef" },
+		"targetCluster": {
+			"resourceId": "/subscriptions/12345678-1234-1234-1234-123456789012/resourceGroups/test-rg/providers/Microsoft.ContainerService/managedClusters/test-cluster",
+			"location": "eastus"
+		}
+	},
+	"node": {
+		"kubelet": {
+			"serverURL": "https://test-cluster.hcp.eastus.azmk8s.io:443",
+			"caCertData": "LS0tLS1CRUdJTi1DRVJUSUZJQ0FURS0tLS0t"
+		},
+		"labels": %s
+	}
+}`
+
+// TestLoadConfigNodeLabels verifies that node label keys are preserved exactly
+// as written in the config file. This is the root motivation: Kubernetes label
+// keys such as "cleanroom.azure.com/flexnode" or "topology.kubernetes.io/zone"
+// contain dots, which Viper's default "." key-path delimiter misinterpreted as
+// nested JSON keys, silently dropping the labels on load.
+func TestLoadConfigNodeLabels(t *testing.T) {
+	tests := []struct {
+		name           string
+		labelsJSON     string
+		expectedLabels map[string]string // only the user-supplied labels; defaults are checked separately
+	}{
+		{
+			name:       "plain labels without dots",
+			labelsJSON: `{"env": "production", "team": "platform"}`,
+			expectedLabels: map[string]string{
+				"env":  "production",
+				"team": "platform",
+			},
+		},
+		{
+			name:       "label key with a single dot segment (kubernetes.io prefix)",
+			labelsJSON: `{"kubernetes.io/nodeReady": "true"}`,
+			expectedLabels: map[string]string{
+				"kubernetes.io/nodeReady": "true",
+			},
+		},
+		{
+			name:       "label key with multiple dot segments (topology prefix)",
+			labelsJSON: `{"topology.kubernetes.io/zone": "eastus-1"}`,
+			expectedLabels: map[string]string{
+				"topology.kubernetes.io/zone": "eastus-1",
+			},
+		},
+		{
+			name:       "label key with three dot segments (org.example.com prefix)",
+			labelsJSON: `{"org.example.com/myLabel": "true"}`,
+			expectedLabels: map[string]string{
+				"org.example.com/myLabel": "true",
+			},
+		},
+		{
+			name: "mixed dotted and plain labels all preserved",
+			labelsJSON: `{
+				"env": "staging",
+				"topology.kubernetes.io/zone": "eastus-1",
+				"cleanroom.azure.com/flexnode": "true",
+				"disktype": "ssd"
+			}`,
+			expectedLabels: map[string]string{
+				"env":                          "staging",
+				"topology.kubernetes.io/zone":  "eastus-1",
+				"cleanroom.azure.com/flexnode": "true",
+				"disktype":                     "ssd",
+			},
+		},
+		{
+			name:       "label value containing dots is preserved",
+			labelsJSON: `{"version": "1.2.3"}`,
+			expectedLabels: map[string]string{
+				"version": "1.2.3",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			configJSON := fmt.Sprintf(baseAzureJSON, tt.labelsJSON)
+			configFile := filepath.Join(t.TempDir(), "config.json")
+			if err := os.WriteFile(configFile, []byte(configJSON), 0o600); err != nil {
+				t.Fatalf("os.WriteFile: %v", err)
+			}
+
+			config, err := LoadConfig(configFile)
+			if err != nil {
+				t.Fatalf("LoadConfig() unexpected error: %v", err)
+			}
+
+			for key, want := range tt.expectedLabels {
+				got, ok := config.Node.Labels[key]
+				if !ok {
+					t.Errorf("label %q not found; got keys: %v", key, labelKeys(config.Node.Labels))
+				} else if got != want {
+					t.Errorf("label %q = %q, want %q", key, got, want)
+				}
+			}
+		})
+	}
+}
+
+// labelKeys returns sorted keys of a map for use in test diagnostics.
+func labelKeys(m map[string]string) []string {
+	keys := make([]string, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	return keys
+}
+
 func TestIsBootstrapTokenConfigured(t *testing.T) {
 	tests := []struct {
 		name     string

pkg/config/structs.go

@@ -172,7 +172,6 @@ func (cfg *Config) IsSPConfigured() bool {
 }
 
 // IsMIConfigured checks if managed identity configuration is provided in the configuration
-// Uses internal flag set during config loading to handle viper's empty object behavior
 func (cfg *Config) IsMIConfigured() bool {
 	return cfg.isMIExplicitlySet
 }