Add call to optional Init function for all plugins (#5899)

agent/agent.go

@@ -39,8 +39,14 @@ func (a *Agent) Run(ctx context.Context) error {
 		return ctx.Err()
 	}
 
+	log.Printf("D! [agent] Initializing plugins")
+	err := a.initPlugins()
+	if err != nil {
+		return err
+	}
+
 	log.Printf("D! [agent] Connecting outputs")
-	err := a.connectOutputs(ctx)
+	err = a.connectOutputs(ctx)
 	if err != nil {
 		return err
 	}
@@ -185,6 +191,11 @@ func (a *Agent) Test(ctx context.Context, waitDuration time.Duration) error {
 	}
 
 	for _, input := range a.Config.Inputs {
+		err := input.Init()
+		if err != nil {
+			return err
+		}
+
 		select {
 		case <-ctx.Done():
 			return nil
@@ -596,6 +607,39 @@ func (a *Agent) flushOnce(
 
 }
 
+// initPlugins runs the Init function on plugins.
+func (a *Agent) initPlugins() error {
+	for _, input := range a.Config.Inputs {
+		err := input.Init()
+		if err != nil {
+			return fmt.Errorf("could not initialize input %s: %v",
+				input.Config.Name, err)
+		}
+	}
+	for _, processor := range a.Config.Processors {
+		err := processor.Init()
+		if err != nil {
+			return fmt.Errorf("could not initialize processor %s: %v",
+				processor.Config.Name, err)
+		}
+	}
+	for _, aggregator := range a.Config.Aggregators {
+		err := aggregator.Init()
+		if err != nil {
+			return fmt.Errorf("could not initialize aggregator %s: %v",
+				aggregator.Config.Name, err)
+		}
+	}
+	for _, output := range a.Config.Outputs {
+		err := output.Init()
+		if err != nil {
+			return fmt.Errorf("could not initialize output %s: %v",
+				output.Config.Name, err)
+		}
+	}
+	return nil
+}
+
 // connectOutputs connects to all outputs.
 func (a *Agent) connectOutputs(ctx context.Context) error {
 	for _, output := range a.Config.Outputs {