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_pub_session.go

@@ -0,0 +1,61 @@
+package agent
+
+import (
+	"context"
+	"github.com/seaweedfs/seaweedfs/weed/mq/client/pub_client"
+	"github.com/seaweedfs/seaweedfs/weed/mq/topic"
+	"github.com/seaweedfs/seaweedfs/weed/pb/mq_agent_pb"
+	"log/slog"
+	"math/rand/v2"
+	"time"
+)
+
+func (a *MessageQueueAgent) StartPublishSession(ctx context.Context, req *mq_agent_pb.StartPublishSessionRequest) (*mq_agent_pb.StartPublishSessionResponse, error) {
+	sessionId := rand.Int64()
+
+	topicPublisher := pub_client.NewTopicPublisher(
+		&pub_client.PublisherConfiguration{
+			Topic:          topic.NewTopic(req.Topic.Namespace, req.Topic.Name),
+			PartitionCount: req.PartitionCount,
+			Brokers:        a.brokersList(),
+			PublisherName:  req.PublisherName,
+			RecordType:     req.RecordType,
+		})
+
+	a.publishersLock.Lock()
+	// remove inactive publishers to avoid memory leak
+	for k, entry := range a.publishers {
+		if entry.lastActiveTsNs == 0 {
+			// this is an active session
+			continue
+		}
+		if time.Unix(0, entry.lastActiveTsNs).Add(10 * time.Hour).Before(time.Now()) {
+			delete(a.publishers, k)
+		}
+	}
+	a.publishers[SessionId(sessionId)] = &SessionEntry[*pub_client.TopicPublisher]{
+		entry: topicPublisher,
+	}
+	a.publishersLock.Unlock()
+
+	return &mq_agent_pb.StartPublishSessionResponse{
+		SessionId: sessionId,
+	}, nil
+}
+
+func (a *MessageQueueAgent) ClosePublishSession(ctx context.Context, req *mq_agent_pb.ClosePublishSessionRequest) (*mq_agent_pb.ClosePublishSessionResponse, error) {
+	var finishErr string
+	a.publishersLock.Lock()
+	publisherEntry, found := a.publishers[SessionId(req.SessionId)]
+	if found {
+		if err := publisherEntry.entry.FinishPublish(); err != nil {
+			finishErr = err.Error()
+			slog.Warn("failed to finish publish", "error", err)
+		}
+		delete(a.publishers, SessionId(req.SessionId))
+	}
+	a.publishersLock.Unlock()
+	return &mq_agent_pb.ClosePublishSessionResponse{
+		Error: finishErr,
+	}, nil
+}