config, api: add API for getting the config checksum (#203)

lib/config/health.go

@@ -15,5 +15,5 @@
 package config
 
 type HealthInfo struct {
-	ConfigVersion uint32 `json:"config_version"`
+	ConfigChecksum uint32 `json:"config_checksum"`
 }

pkg/manager/config/config.go

@@ -15,6 +15,8 @@
 package config
 
 import (
+	"bytes"
+	"hash/crc32"
 	"os"
 	"time"
 
@@ -74,8 +76,9 @@ func (e *ConfigManager) SetTOMLConfig(data []byte) error {
 		return err
 	}
 
-	e.sts.current = base
-	e.sts.version++
+	if err := e.setCurrentConfig(base); err != nil {
+		return err
+	}
 
 	for _, list := range e.sts.listeners {
 		list <- base.Clone()
@@ -84,18 +87,28 @@ func (e *ConfigManager) SetTOMLConfig(data []byte) error {
 	return nil
 }
 
+func (e *ConfigManager) setCurrentConfig(cfg *config.Config) error {
+	e.sts.current = cfg
+	var buf bytes.Buffer
+	if err := toml.NewEncoder(&buf).Encode(cfg); err != nil {
+		return err
+	}
+	e.sts.checksum = crc32.ChecksumIEEE(buf.Bytes())
+	return nil
+}
+
 func (e *ConfigManager) GetConfig() *config.Config {
 	e.sts.Lock()
 	v := e.sts.current
 	e.sts.Unlock()
 	return v
 }
 
-func (e *ConfigManager) GetConfigVersion() uint32 {
+func (e *ConfigManager) GetConfigChecksum() uint32 {
 	e.sts.Lock()
-	v := e.sts.version
+	c := e.sts.checksum
 	e.sts.Unlock()
-	return v
+	return c
 }
 
 func (e *ConfigManager) WatchConfig() <-chan *config.Config {

pkg/manager/config/config_test.go

@@ -163,3 +163,18 @@ func TestConfigRemove(t *testing.T) {
 	require.NoError(t, os.WriteFile(tmpcfg, []byte(`proxy.addr = "vv"`), 0644))
 	require.Eventually(t, func() bool { return cfgmgr.GetConfig().Proxy.Addr == "vv" }, time.Second, 100*time.Millisecond)
 }
+
+func TestChecksum(t *testing.T) {
+	cfgmgr, _ := testConfigManager(t, "")
+	c1 := cfgmgr.GetConfigChecksum()
+	require.NoError(t, cfgmgr.SetTOMLConfig([]byte(`proxy.addr = "gg"`)))
+	c2 := cfgmgr.GetConfigChecksum()
+	require.NoError(t, cfgmgr.SetTOMLConfig([]byte(`proxy.addr = "vv"`)))
+	c3 := cfgmgr.GetConfigChecksum()
+	require.NoError(t, cfgmgr.SetTOMLConfig([]byte(`proxy.addr="gg"`)))
+	c4 := cfgmgr.GetConfigChecksum()
+	require.Equal(t, c2, c4)
+	require.NotEqual(t, c1, c2)
+	require.NotEqual(t, c1, c3)
+	require.NotEqual(t, c2, c3)
+}

pkg/manager/config/manager.go

@@ -56,7 +56,7 @@ type ConfigManager struct {
 		sync.Mutex
 		listeners []chan<- *config.Config
 		current   *config.Config
-		version   uint32
+		checksum  uint32
 	}
 }
 

pkg/server/api/debug.go

@@ -24,7 +24,7 @@ import (
 
 func (h *HTTPServer) DebugHealth(c *gin.Context) {
 	c.JSON(http.StatusOK, config.HealthInfo{
-		ConfigVersion: h.mgr.cfg.GetConfigVersion(),
+		ConfigChecksum: h.mgr.cfg.GetConfigChecksum(),
 	})
 }