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_sub_session.go

@@ -0,0 +1,57 @@
+package agent
+
+import (
+	"context"
+	"github.com/seaweedfs/seaweedfs/weed/mq/client/sub_client"
+	"github.com/seaweedfs/seaweedfs/weed/mq/topic"
+	"github.com/seaweedfs/seaweedfs/weed/pb/mq_agent_pb"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"math/rand/v2"
+	"time"
+)
+
+func (a *MessageQueueAgent) StartSubscribeSession(ctx context.Context, req *mq_agent_pb.StartSubscribeSessionRequest) (*mq_agent_pb.StartSubscribeSessionResponse, error) {
+	sessionId := rand.Int64()
+
+	subscriberConfig := &sub_client.SubscriberConfiguration{
+		ConsumerGroup:           req.ConsumerGroup,
+		ConsumerGroupInstanceId: req.ConsumerGroupInstanceId,
+		GrpcDialOption:          grpc.WithTransportCredentials(insecure.NewCredentials()),
+		MaxPartitionCount:       req.MaxSubscribedPartitions,
+		SlidingWindowSize:       req.SlidingWindowSize,
+	}
+
+	contentConfig := &sub_client.ContentConfiguration{
+		Topic:            topic.FromPbTopic(req.Topic),
+		Filter:           req.Filter,
+		PartitionOffsets: req.PartitionOffsets,
+	}
+
+	topicSubscriber := sub_client.NewTopicSubscriber(
+		a.brokersList(),
+		subscriberConfig,
+		contentConfig,
+		make(chan sub_client.KeyedOffset, 1024),
+	)
+
+	a.subscribersLock.Lock()
+	// remove inactive publishers to avoid memory leak
+	for k, entry := range a.subscribers {
+		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.subscribers, k)
+		}
+	}
+	a.subscribers[SessionId(sessionId)] = &SessionEntry[*sub_client.TopicSubscriber]{
+		entry: topicSubscriber,
+	}
+	a.subscribersLock.Unlock()
+
+	return &mq_agent_pb.StartSubscribeSessionResponse{
+		SessionId: sessionId,
+	}, nil
+}