Add message queue agent (#6463)

* scaffold message queue agent

* adjust proto, add mq_agent

* add agent client implementation

* remove unused function

* agent publish server implementation

* adding agent

weed/mq/agent/agent_grpc_publish.go

@@ -0,0 +1,43 @@
+package agent
+
+import (
+	"fmt"
+	"github.com/seaweedfs/seaweedfs/weed/pb/mq_agent_pb"
+	"time"
+)
+
+func (a *MessageQueueAgent) PublishRecordRequest(stream mq_agent_pb.SeaweedMessagingAgent_PublishRecordServer) error {
+	m, err := stream.Recv()
+	if err != nil {
+		return err
+	}
+	a.publishersLock.RLock()
+	publisherEntry, found := a.publishers[SessionId(m.SessionId)]
+	a.publishersLock.RUnlock()
+	if !found {
+		return fmt.Errorf("publish session id %d not found", m.SessionId)
+	}
+	defer func() {
+		publisherEntry.lastActiveTsNs = time.Now().UnixNano()
+	}()
+	publisherEntry.lastActiveTsNs = 0
+
+	if m.Value != nil {
+		if err := publisherEntry.entry.PublishRecord(m.Key, m.Value); err != nil {
+			return err
+		}
+	}
+
+	for {
+		m, err := stream.Recv()
+		if err != nil {
+			return err
+		}
+		if m.Value == nil {
+			continue
+		}
+		if err := publisherEntry.entry.PublishRecord(m.Key, m.Value); err != nil {
+			return err
+		}
+	}
+}