allow protection from invalid config values (#19460)

we have had numerous reports on some config
values not having default values, causing
features misbehaving and not having default
values set properly.

This PR tries to address all these concerns
once and for all.

Each new sub-system that gets added

- must check for invalid keys
- must have default values set
- must not "return err" when being saved into
  a global state() instead collate as part of
  other subsystem errors allow other sub-systems
  to independently initialize.

internal/config/scanner/scanner.go

@@ -114,15 +114,44 @@ var DefaultKVS = config.KVS{
 
 // LookupConfig - lookup config and override with valid environment settings if any.
 func LookupConfig(kvs config.KVS) (cfg Config, err error) {
+	cfg = Config{
+		ExcessVersions: 100,
+		ExcessFolders:  50000,
+		IdleMode:       0, // Default is on
+	}
+
 	if err = config.CheckValidKeys(config.ScannerSubSys, kvs, DefaultKVS); err != nil {
 		return cfg, err
 	}
 
+	excessVersions, err := strconv.ParseInt(env.Get(EnvExcessVersions, kvs.GetWithDefault(ExcessVersions, DefaultKVS)), 10, 64)
+	if err != nil {
+		return cfg, err
+	}
+	cfg.ExcessVersions = excessVersions
+
+	excessFolders, err := strconv.ParseInt(env.Get(EnvExcessFolders, kvs.GetWithDefault(ExcessFolders, DefaultKVS)), 10, 64)
+	if err != nil {
+		return cfg, err
+	}
+	cfg.ExcessFolders = excessFolders
+
+	switch idleSpeed := env.Get(EnvIdleSpeed, kvs.GetWithDefault(IdleSpeed, DefaultKVS)); idleSpeed {
+	case "", config.EnableOn:
+		cfg.IdleMode = 0
+	case config.EnableOff:
+		cfg.IdleMode = 1
+	default:
+		return cfg, fmt.Errorf("unknown value: '%s'", idleSpeed)
+	}
+
 	// Stick to loading deprecated config/env if they are already set, and the Speed value
 	// has not been changed from its "default" value, if it has been changed honor new settings.
 	if kvs.GetWithDefault(Speed, DefaultKVS) == "default" {
 		if kvs.Get(Delay) != "" && kvs.Get(MaxWait) != "" {
-			return lookupDeprecatedScannerConfig(kvs)
+			if err = lookupDeprecatedScannerConfig(kvs, &cfg); err != nil {
+				return cfg, err
+			}
 		}
 	}
 
@@ -141,38 +170,17 @@ func LookupConfig(kvs config.KVS) (cfg Config, err error) {
 		return cfg, fmt.Errorf("unknown '%s' value", speed)
 	}
 
-	switch idleSpeed := env.Get(EnvIdleSpeed, kvs.GetWithDefault(IdleSpeed, DefaultKVS)); idleSpeed {
-	case "", config.EnableOn:
-		cfg.IdleMode = 0
-	case config.EnableOff:
-		cfg.IdleMode = 1
-	default:
-		return cfg, fmt.Errorf("unknown value: '%s'", idleSpeed)
-	}
-
-	excessVersions, err := strconv.ParseInt(env.Get(EnvExcessVersions, kvs.GetWithDefault(ExcessVersions, DefaultKVS)), 10, 64)
-	if err != nil {
-		return cfg, err
-	}
-	cfg.ExcessVersions = excessVersions
-
-	excessFolders, err := strconv.ParseInt(env.Get(EnvExcessFolders, kvs.GetWithDefault(ExcessFolders, DefaultKVS)), 10, 64)
-	if err != nil {
-		return cfg, err
-	}
-	cfg.ExcessFolders = excessFolders
-
 	return cfg, nil
 }
 
-func lookupDeprecatedScannerConfig(kvs config.KVS) (cfg Config, err error) {
+func lookupDeprecatedScannerConfig(kvs config.KVS, cfg *Config) (err error) {
 	delay := env.Get(EnvDelayLegacy, "")
 	if delay == "" {
 		delay = env.Get(EnvDelay, kvs.GetWithDefault(Delay, DefaultKVS))
 	}
 	cfg.Delay, err = strconv.ParseFloat(delay, 64)
 	if err != nil {
-		return cfg, err
+		return err
 	}
 	maxWait := env.Get(EnvMaxWaitLegacy, "")
 	if maxWait == "" {
@@ -180,7 +188,7 @@ func lookupDeprecatedScannerConfig(kvs config.KVS) (cfg Config, err error) {
 	}
 	cfg.MaxWait, err = time.ParseDuration(maxWait)
 	if err != nil {
-		return cfg, err
+		return err
 	}
 	cycle := env.Get(EnvCycle, kvs.GetWithDefault(Cycle, DefaultKVS))
 	if cycle == "" {
@@ -188,7 +196,7 @@ func lookupDeprecatedScannerConfig(kvs config.KVS) (cfg Config, err error) {
 	}
 	cfg.Cycle, err = time.ParseDuration(cycle)
 	if err != nil {
-		return cfg, err
+		return err
 	}
-	return cfg, nil
+	return nil
 }