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/client/agent_client/SubscribeSession.go

@@ -0,0 +1,63 @@
+package agent_client
+
+import (
+	"context"
+	"fmt"
+	"github.com/seaweedfs/seaweedfs/weed/mq/topic"
+	"github.com/seaweedfs/seaweedfs/weed/pb"
+	"github.com/seaweedfs/seaweedfs/weed/pb/mq_agent_pb"
+	"github.com/seaweedfs/seaweedfs/weed/pb/schema_pb"
+	"google.golang.org/grpc"
+)
+
+type SubscribeOption struct {
+	ConsumerGroup           string
+	ConsumerGroupInstanceId string
+	Topic                   topic.Topic
+	Filter                  string
+	MaxSubscribedPartitions int32
+	PerPartitionConcurrency int32
+}
+
+type SubscribeSession struct {
+	Option    *SubscribeOption
+	stream    grpc.BidiStreamingClient[mq_agent_pb.SubscribeRecordRequest, mq_agent_pb.SubscribeRecordResponse]
+	sessionId int64
+}
+
+func NewSubscribeSession(agentAddress string, option *SubscribeOption) (*SubscribeSession, error) {
+	// call local agent grpc server to create a new session
+	clientConn, err := pb.GrpcDial(context.Background(), agentAddress, true, grpc.WithInsecure())
+	if err != nil {
+		return nil, fmt.Errorf("dial agent server %s: %v", agentAddress, err)
+	}
+	agentClient := mq_agent_pb.NewSeaweedMessagingAgentClient(clientConn)
+
+	resp, err := agentClient.StartSubscribeSession(context.Background(), &mq_agent_pb.StartSubscribeSessionRequest{
+		ConsumerGroup:           option.ConsumerGroup,
+		ConsumerGroupInstanceId: option.ConsumerGroupInstanceId,
+		Topic: &schema_pb.Topic{
+			Namespace: option.Topic.Namespace,
+			Name:      option.Topic.Name,
+		},
+		MaxSubscribedPartitions: option.MaxSubscribedPartitions,
+		Filter:                  option.Filter,
+	})
+	if err != nil {
+		return nil, err
+	}
+	if resp.Error != "" {
+		return nil, fmt.Errorf("start subscribe session: %v", resp.Error)
+	}
+
+	stream, err := agentClient.SubscribeRecord(context.Background())
+	if err != nil {
+		return nil, fmt.Errorf("subscribe record: %v", err)
+	}
+
+	return &SubscribeSession{
+		Option:    option,
+		stream:    stream,
+		sessionId: resp.SessionId,
+	}, nil
+}