Config items: honour persisted config & support run-time change

This commit addresses two issues/limitations related to global config items:

1. nodeagent and zedagent do not support runtime changes of global config items.
   They only apply the very first received instance of `ConfigItemValueMap`
   and ignore any subsequent changes. This for example means, that
   changing `timer.reboot.no.network` for an already onboarded and
   running device has no effect - the change is ignored.
   To support run-time change of config items is as simple as changing
   a single if condition inside the handler for `ConfigItemValueMap` subscription.

2. Few months ago the upgradeconverter was improved to support override
   of config items via the config partition. However, these changes
   no longer take into account potentially persisted config from a
   previous run. Currently, if config items are not overridden
   via config partition (`/config/GlobalConfig/global.json` does not exist),
   the updateconverter will immediately apply default values. This
   commits makes changes to check for persisted config items before
   restoring to defaults.

Signed-off-by: Milan Lenco <[email protected]>

Author: milan-zededa

pkg/pillar/cmd/nodeagent/nodeagent.go

@@ -412,7 +412,7 @@ func handleGlobalConfigImpl(ctxArg interface{}, key string,
 	var gcp *types.ConfigItemValueMap
 	debug, gcp = agentlog.HandleGlobalConfig(log, ctxPtr.subGlobalConfig, agentName,
 		debugOverride, ctxPtr.agentBaseContext.Logger)
-	if gcp != nil && !ctxPtr.GCInitialized {
+	if gcp != nil {
 		ctxPtr.globalConfig = gcp
 		ctxPtr.GCInitialized = true
 	}

pkg/pillar/cmd/upgradeconverter/applydefaultconfigitem.go

@@ -72,18 +72,28 @@ func importFromConfigPartition(ctxPtr *ucContext) error {
 
 	persistStatusFile := ctxPtr.newConfigItemValueMapFile()
 	globalConfigExists := fileExists(importGlobalConfigFile)
+	persistedConfigExists := fileExists(persistStatusFile)
 
 	if globalConfigExists {
+		log.Noticef("Importing config items from %s", importGlobalConfigFile)
 		globalConfigPtr, err = parseFile(importGlobalConfigFile)
 		if err != nil {
 			log.Errorf("Error parsing configuration from file: %s, %s", importGlobalConfigFile, err)
 			return err
 		}
+	} else if persistedConfigExists {
+		log.Noticef("Reusing persisted config items from the previous run")
+		globalConfigPtr, err = parseFile(persistStatusFile)
+		if err != nil {
+			log.Errorf("Error parsing configuration from file: %s, %s", persistStatusFile, err)
+			return err
+		}
 	} else {
 		log.Noticef("No existing ConfigItemValueMap; creating new %s",
 			persistStatusFile)
 		globalConfigPtr = types.NewConfigItemValueMap()
 	}
+
 	keyData, keyDataValid := readAuthorizedKeys(baseAuthorizedKeysFile)
 	if len(keyData) != 0 {
 		log.Functionf("Found the key data in %s", baseAuthorizedKeysFile)
@@ -110,7 +120,7 @@ func importFromConfigPartition(ctxPtr *ucContext) error {
 		os.Remove(importGlobalConfigFile)
 		log.Functionf("Deleted %s file from /config/", importGlobalConfigFile)
 	}
-	log.Tracef("upgradeconverter.applyDefaultConfigItem done")
+	log.Tracef("upgradeconverter.importFromConfigPartition done")
 	return nil
 }
 

pkg/pillar/cmd/zedagent/zedagent.go

@@ -1882,7 +1882,7 @@ func handleGlobalConfigImpl(ctxArg interface{}, key string,
 	var gcp *types.ConfigItemValueMap
 	debug, gcp = agentlog.HandleGlobalConfig(log, ctx.subGlobalConfig, agentName,
 		debugOverride, logger)
-	if gcp != nil && !ctx.GCInitialized {
+	if gcp != nil {
 		ctx.globalConfig = *gcp
 		ctx.GCInitialized = true
 		ctx.gcpMaintenanceMode = gcp.GlobalValueTriState(types.MaintenanceMode)