Fix #403: Change to checking to see if a metric's policy has any rule…

…s before processing config

control/control.go

@@ -402,7 +402,10 @@ func (p *pluginControl) validateMetricTypeSubscription(mt core.RequestedMetric,
 	}
 	m.config = cd
 
-	if m.policy != nil {
+	// When a metric is added to the MetricCatalog, the policy of rules defined by the plugin is added to the metric's policy.
+	// If no rules are defined for a metric, we set the metric's policy to an empty ConfigPolicyNode.
+	// Checking m.policy for nil will not work, we need to check if rules are nil.
+	if m.policy.HasRules() {
 		if m.Config() == nil {
 			perrs = append(perrs, perror.New(errors.New(fmt.Sprintf("Policy defined for metric, (%s) version (%d), but no config defined in manifest", mt.Namespace(), mt.Version()))))
 			return nil, perrs

control/metrics.go

@@ -73,6 +73,7 @@ type metricType struct {
 
 type processesConfigData interface {
 	Process(map[string]ctypes.ConfigValue) (*map[string]ctypes.ConfigValue, *cpolicy.ProcessingErrors)
+	HasRules() bool
 }
 
 func newMetricType(ns []string, last time.Time, plugin *loadedPlugin) *metricType {

control/plugin/cpolicy/node.go

@@ -146,6 +146,13 @@ func (p *ConfigPolicyNode) RulesAsTable() []RuleTable {
 	return rt
 }
 
+func (c *ConfigPolicyNode) HasRules() bool {
+	if len(c.rules) > 0 {
+		return true
+	}
+	return false
+}
+
 // Validates and returns a processed policy node or nil and error if validation has failed
 func (c *ConfigPolicyNode) Process(m map[string]ctypes.ConfigValue) (*map[string]ctypes.ConfigValue, *ProcessingErrors) {
 	c.mutex.Lock()