fix: use monotonic counter for tracking config changes

See ory/oathkeeper#557 (comment)
See ory/x#216

go.mod

@@ -18,7 +18,6 @@ require (
 	github.com/spf13/pflag v1.0.3
 	github.com/stretchr/testify v1.4.0
 	github.com/subosito/gotenv v1.2.0
-	golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37 // indirect
 	golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9 // indirect
 	golang.org/x/text v0.3.2 // indirect
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect

go.sum

@@ -55,13 +55,9 @@ github.com/subosito/gotenv v1.2.0 h1:Slr1R9HxAlEKefgq5jn9U+DnETlIUa6HfgEzj0g5d7s
 github.com/subosito/gotenv v1.2.0/go.mod h1:N0PQaV/YGNqwC0u51sEeR/aUtSLEXKX9iv69rRypqCw=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2 h1:VklqNMn3ovrHsnt90PveolxSbWFaJdECFbxSq0Mqo2M=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37 h1:cg5LA/zNPRzIXIWSCxQW10Rvpy94aQh3LT/ShoCpkHw=
-golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a h1:1BGLXjeY4akVXGgbC9HugT3Jv3hCI0z56oJR5vAMgBU=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191005200804-aed5e4c7ecf9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9 h1:1/DFK4b7JH8DmkqhUk48onnSfrPzImPoVxuomtbT2nk=
 golang.org/x/sys v0.0.0-20200124204421-9fbb57f87de9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

viper.go

@@ -32,6 +32,7 @@ import (
 	"reflect"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/dgraph-io/ristretto"
@@ -196,7 +197,7 @@ type Viper struct {
 	configFile        string
 	configType        string
 	configPermissions os.FileMode
-	configChangedAt   time.Time
+	configVersion     uint32
 	envPrefix         string
 
 	automaticEnvApplied bool
@@ -232,7 +233,7 @@ func New() *Viper {
 	v := new(Viper)
 	v.keyDelim = "."
 	v.configName = "config"
-	v.configChangedAt = time.Now()
+	v.configVersion = 1
 	v.configPermissions = os.FileMode(0644)
 	v.fs = afero.NewOsFs()
 	v.config = make(map[string]interface{})
@@ -516,13 +517,15 @@ func (v *Viper) ConfigFileUsed() string {
 	return v.configFile
 }
 
-// ConfigChangeAt returns the time of the last config change.
-func ConfigChangeAt() time.Time { return v.ConfigChangeAt() }
-func (v *Viper) ConfigChangeAt() time.Time {
+// ConfigChanges returns number of changes to the config.
+// The number of changes increases each time
+// the configuration is changed or reloaded.
+func ConfigChanges() uint32 { return v.ConfigVersion() }
+func (v *Viper) ConfigVersion() uint32 {
 	v.lock.RLock()
 	defer v.lock.RUnlock()
 
-	return v.configChangedAt
+	return v.configVersion
 }
 
 // AddConfigPath adds a path for Viper to search for the config file in.
@@ -1532,7 +1535,7 @@ func (v *Viper) ReadInConfig() error {
 	v.lock.Lock()
 	v.cache.Clear()
 	v.config = config
-	v.configChangedAt = time.Now()
+	atomic.AddUint32(&v.configVersion, 1)
 	v.lock.Unlock()
 
 	return nil
@@ -1545,7 +1548,7 @@ func (v *Viper) SetRawConfig(config map[string]interface{}) {
 	defer v.lock.Unlock()
 	insensitiviseMap(config)
 	v.config = config
-	v.configChangedAt = time.Now()
+	atomic.AddUint32(&v.configVersion, 1)
 	v.cache.Clear()
 }
 
@@ -1578,7 +1581,7 @@ func (v *Viper) ReadConfig(in io.Reader) error {
 	defer v.lock.Unlock()
 	v.cache.Clear()
 	v.config = make(map[string]interface{})
-	v.configChangedAt = time.Now()
+	atomic.AddUint32(&v.configVersion, 1)
 	return v.unmarshalReader(in, v.config)
 }
 
@@ -1603,7 +1606,7 @@ func (v *Viper) MergeConfigMap(cfg map[string]interface{}) error {
 	}
 	insensitiviseMap(cfg)
 	mergeMaps(cfg, v.config, nil)
-	v.configChangedAt = time.Now()
+	atomic.AddUint32(&v.configVersion, 1)
 	v.lock.Unlock()
 	return nil
 }

viper_test.go

@@ -2273,39 +2273,37 @@ func TestConfigChangedAt(t *testing.T) {
 	t.Run("read config", func(t *testing.T) {
 		Reset()
 		SetConfigType("yml")
-		changedAt := ConfigChangeAt()
+		changedAt := ConfigChanges()
 
 		require.NoError(t, ReadConfig(bytes.NewBufferString(`foo: bar`)))
 
 		// Check that changedAt is different to initial
-		firstRead := ConfigChangeAt()
-		assert.NotEqual(t, changedAt.UnixNano(), firstRead.UnixNano())
+		assert.Equal(t, changedAt, ConfigChanges()-1)
 
 		require.NoError(t, ReadConfig(bytes.NewBufferString(`foo: baz`)))
 
-		// Check that changedAt is different to last read
-		assert.NotEqual(t, firstRead.UnixNano(), ConfigChangeAt().UnixNano())
+		assert.Equal(t, changedAt, ConfigChanges()-2)
 	})
 
 	t.Run("merge config", func(t *testing.T) {
 		Reset()
 		SetConfigType("yml")
-		changedAt := ConfigChangeAt()
+		changedAt := ConfigChanges()
 
 		if err := v.ReadConfig(bytes.NewBuffer(yamlMergeExampleTgt)); err != nil {
 			t.Fatal(err)
 		}
 
 		// Check that changedAt is different to initial
-		firstRead := ConfigChangeAt()
-		assert.NotEqual(t, changedAt.UnixNano(), firstRead.UnixNano())
+		firstRead := ConfigChanges()
+		assert.NotEqual(t, changedAt, firstRead)
 
 		if err := v.MergeConfig(bytes.NewBuffer(yamlMergeExampleSrc)); err != nil {
 			t.Fatal(err)
 		}
 
 		// Check that changedAt is different to last read
-		assert.NotEqual(t, firstRead.UnixNano(), ConfigChangeAt().UnixNano())
+		assert.NotEqual(t, firstRead, ConfigChanges())
 	})
 
 	t.Run("watch file", func(t *testing.T) {
@@ -2316,7 +2314,7 @@ func TestConfigChangedAt(t *testing.T) {
 
 		// given a `config.yaml` file being watched
 		v, configFile, cleanup := newViperWithConfigFile(t)
-		changedAt := v.ConfigChangeAt()
+		changedAt := v.ConfigVersion()
 		defer cleanup()
 
 		_, err := os.Stat(configFile)
@@ -2337,7 +2335,7 @@ func TestConfigChangedAt(t *testing.T) {
 		require.Nil(t, err)
 
 		// Check that changedAt is different
-		assert.NotEqual(t, changedAt.UnixNano(), v.ConfigChangeAt().UnixNano())
+		assert.NotEqual(t, changedAt, v.ConfigVersion())
 	})
 }