add check for underAgent and DiskQueue

libbeat/cmd/instance/beat.go

@@ -64,8 +64,10 @@ import (
 	"github.com/elastic/beats/v7/libbeat/outputs/elasticsearch"
 	"github.com/elastic/beats/v7/libbeat/plugin"
 	"github.com/elastic/beats/v7/libbeat/pprof"
+	"github.com/elastic/beats/v7/libbeat/publisher"
 	"github.com/elastic/beats/v7/libbeat/publisher/pipeline"
 	"github.com/elastic/beats/v7/libbeat/publisher/processing"
+	"github.com/elastic/beats/v7/libbeat/publisher/queue/diskqueue"
 	"github.com/elastic/beats/v7/libbeat/version"
 	"github.com/elastic/elastic-agent-libs/config"
 	"github.com/elastic/elastic-agent-libs/file"
@@ -838,6 +840,10 @@ func (b *Beat) configure(settings Settings) error {
 	if err != nil {
 		return err
 	}
+	err = checkAgentDiskQueue(&b.Config)
+	if err != nil {
+		return err
+	}
 
 	if err := b.Manager.CheckRawConfig(b.RawConfig); err != nil {
 		return err
@@ -1513,3 +1519,20 @@ func (bc *beatConfig) Validate() error {
 	}
 	return nil
 }
+
+// checkAgentDiskQueue should be run after management.NewManager() so
+// that publisher.UnderAgent will be set with correct value
+func checkAgentDiskQueue(bc *beatConfig) error {
+	//restriction is only if under agent
+	if !publisher.UnderAgent() {
+		return nil
+	}
+	//default queue settings are always allowed
+	if !bc.Pipeline.Queue.IsSet() {
+		return nil
+	}
+	if bc.Pipeline.Queue.Config().Enabled() && bc.Pipeline.Queue.Name() == diskqueue.QueueType {
+		return fmt.Errorf("disk queue is not supported under elastic-agent")
+	}
+	return nil
+}