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_subscribe.go

@@ -0,0 +1,75 @@
+package agent
+
+import (
+	"fmt"
+	"github.com/seaweedfs/seaweedfs/weed/glog"
+	"github.com/seaweedfs/seaweedfs/weed/mq/client/sub_client"
+	"github.com/seaweedfs/seaweedfs/weed/pb/mq_agent_pb"
+	"github.com/seaweedfs/seaweedfs/weed/pb/mq_pb"
+	"github.com/seaweedfs/seaweedfs/weed/pb/schema_pb"
+	"google.golang.org/protobuf/proto"
+	"time"
+)
+
+func (a *MessageQueueAgent) SubscribeRecordRequest(stream mq_agent_pb.SeaweedMessagingAgent_SubscribeRecordServer) error {
+	// the first message is the subscribe request
+	// it should only contain the session id
+	m, err := stream.Recv()
+	if err != nil {
+		return err
+	}
+	a.subscribersLock.RLock()
+	subscriberEntry, found := a.subscribers[SessionId(m.SessionId)]
+	a.subscribersLock.RUnlock()
+	if !found {
+		return fmt.Errorf("subscribe session id %d not found", m.SessionId)
+	}
+	defer func() {
+		subscriberEntry.lastActiveTsNs = time.Now().UnixNano()
+	}()
+	subscriberEntry.lastActiveTsNs = 0
+
+	var lastErr error
+	subscriberEntry.entry.SetOnDataMessageFn(func(m *mq_pb.SubscribeMessageResponse_Data) {
+		record := &schema_pb.RecordValue{}
+		err := proto.Unmarshal(m.Data.Value, record)
+		if err != nil {
+			if lastErr == nil {
+				lastErr = err
+			}
+			return
+		}
+		if sendErr := stream.Send(&mq_agent_pb.SubscribeRecordResponse{
+			Key:   m.Data.Key,
+			Value: record,
+			TsNs:  m.Data.TsNs,
+		}); sendErr != nil {
+			if lastErr == nil {
+				lastErr = sendErr
+			}
+		}
+	})
+
+	go func() {
+		subErr := subscriberEntry.entry.Subscribe()
+		if subErr != nil {
+			glog.V(0).Infof("subscriber %d subscribe: %v", m.SessionId, subErr)
+			if lastErr == nil {
+				lastErr = subErr
+			}
+		}
+	}()
+
+	for {
+		m, err := stream.Recv()
+		if err != nil {
+			return err
+		}
+		if m != nil {
+			subscriberEntry.entry.PartitionOffsetChan <- sub_client.KeyedOffset{
+				Key:    m.AckKey,
+				Offset: m.AckSequence,
+			}
+		}
+	}
+}