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/pb/mq_agent.proto

@@ -0,0 +1,95 @@
+syntax = "proto3";
+
+package messaging_pb;
+
+import "mq_schema.proto";
+
+option go_package = "github.com/seaweedfs/seaweedfs/weed/pb/mq_agent_pb";
+option java_package = "seaweedfs.mq_agent";
+option java_outer_classname = "MessageQueueAgentProto";
+
+//////////////////////////////////////////////////
+
+service SeaweedMessagingAgent {
+
+    // Publishing
+    rpc StartPublishSession (StartPublishSessionRequest) returns (StartPublishSessionResponse) {
+    }
+    rpc ClosePublishSession (ClosePublishSessionRequest) returns (ClosePublishSessionResponse) {
+    }
+    rpc PublishRecord (stream PublishRecordRequest) returns (stream PublishRecordResponse) {
+    }
+
+    // Subscribing
+    rpc StartSubscribeSession (StartSubscribeSessionRequest) returns (StartSubscribeSessionResponse) {
+    }
+    rpc CloseSubscribeSession (CloseSubscribeSessionRequest) returns (CloseSubscribeSessionResponse) {
+    }
+    rpc SubscribeRecord (stream SubscribeRecordRequest) returns (stream SubscribeRecordResponse) {
+    }
+
+}
+
+//////////////////////////////////////////////////
+message StartPublishSessionRequest {
+    schema_pb.Topic topic = 1;
+    int32 partition_count = 2;
+    schema_pb.RecordType record_type = 3;
+    string publisher_name = 4;
+}
+message StartPublishSessionResponse {
+    string error = 1;
+    int64 session_id = 2;
+}
+message ClosePublishSessionRequest {
+    int64 session_id = 1;
+}
+message ClosePublishSessionResponse {
+    string error = 1;
+}
+
+//////////////////////////////////////////////////
+message PublishRecordRequest {
+    int64 session_id = 1; // session_id is required for the first record
+    bytes key = 2;
+    schema_pb.RecordValue value = 3;
+}
+message PublishRecordResponse {
+    int64 ack_sequence = 1;
+    string error = 2;
+}
+//////////////////////////////////////////////////
+message StartSubscribeSessionRequest {
+    string consumer_group = 1;
+    string consumer_group_instance_id = 2;
+    schema_pb.Topic topic = 4;
+    repeated schema_pb.PartitionOffset partition_offsets = 5;
+    string filter = 6;
+    int32 max_subscribed_partitions = 8;
+    int32 sliding_window_size = 9;
+}
+message StartSubscribeSessionResponse {
+    string error = 1;
+    int64 session_id = 2;
+}
+message CloseSubscribeSessionRequest {
+    int64 session_id = 1;
+}
+message CloseSubscribeSessionResponse {
+    string error = 1;
+}
+//////////////////////////////////////////////////
+message SubscribeRecordRequest {
+    int64 session_id = 1; // session_id is required for the first record
+    int64 ack_sequence = 2;
+    bytes ack_key = 3;
+}
+message SubscribeRecordResponse {
+    bytes key = 2;
+    schema_pb.RecordValue value = 3;
+    int64 ts_ns = 4;
+    string error = 5;
+    bool is_end_of_stream = 6;
+    bool is_end_of_topic = 7;
+}
+//////////////////////////////////////////////////