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/publish_session.go

@@ -0,0 +1,70 @@
+package agent_client
+
+import (
+	"context"
+	"fmt"
+	"github.com/seaweedfs/seaweedfs/weed/mq/schema"
+	"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 PublishSession struct {
+	schema         *schema.Schema
+	partitionCount int
+	publisherName  string
+	stream         grpc.BidiStreamingClient[mq_agent_pb.PublishRecordRequest, mq_agent_pb.PublishRecordResponse]
+	sessionId      int64
+}
+
+func NewPublishSession(agentAddress string, topicSchema *schema.Schema, partitionCount int, publisherName string) (*PublishSession, 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.StartPublishSession(context.Background(), &mq_agent_pb.StartPublishSessionRequest{
+		Topic: &schema_pb.Topic{
+			Namespace: topicSchema.Namespace,
+			Name:      topicSchema.Name,
+		},
+		PartitionCount: int32(partitionCount),
+		RecordType:     topicSchema.RecordType,
+		PublisherName:  publisherName,
+	})
+	if err != nil {
+		return nil, err
+	}
+	if resp.Error != "" {
+		return nil, fmt.Errorf("start publish session: %v", resp.Error)
+	}
+
+	stream, err := agentClient.PublishRecord(context.Background())
+	if err != nil {
+		return nil, fmt.Errorf("publish record: %v", err)
+	}
+
+	return &PublishSession{
+		schema:         topicSchema,
+		partitionCount: partitionCount,
+		publisherName:  publisherName,
+		stream:         stream,
+		sessionId:      resp.SessionId,
+	}, nil
+}
+
+func (a *PublishSession) CloseSession() error {
+	if a.schema == nil {
+		return nil
+	}
+	err := a.stream.CloseSend()
+	if err != nil {
+		return fmt.Errorf("close send: %v", err)
+	}
+	a.schema = nil
+	return err
+}