add raft_leader_info command to always display output of current leader

src/Commands.cc

@@ -83,6 +83,7 @@ struct cmdMapInit {
     redis_cmd_map["raft_handshake"] = {RedisCommand::RAFT_HANDSHAKE, CommandType::RAFT};
     redis_cmd_map["raft_append_entries"] = {RedisCommand::RAFT_APPEND_ENTRIES, CommandType::RAFT};
     redis_cmd_map["raft_info"] = {RedisCommand::RAFT_INFO, CommandType::RAFT};
+    redis_cmd_map["raft_leader_info"] = {RedisCommand::RAFT_LEADER_INFO, CommandType::RAFT};
     redis_cmd_map["raft_request_vote"] = {RedisCommand::RAFT_REQUEST_VOTE, CommandType::RAFT};
     redis_cmd_map["raft_fetch"] = {RedisCommand::RAFT_FETCH, CommandType::RAFT};
     redis_cmd_map["raft_checkpoint"] = {RedisCommand::RAFT_CHECKPOINT, CommandType::RAFT};

src/Commands.hh

@@ -87,6 +87,7 @@ enum class RedisCommand {
   RAFT_HANDSHAKE,
   RAFT_APPEND_ENTRIES,
   RAFT_INFO,
+  RAFT_LEADER_INFO,
   RAFT_REQUEST_VOTE,
   RAFT_FETCH,
   RAFT_CHECKPOINT,

src/raft/RaftDispatcher.cc

@@ -49,6 +49,17 @@ LinkStatus RaftDispatcher::dispatch(Connection *conn, RedisRequest &req) {
 
       return conn->statusVector(this->info().toVector());
     }
+    case RedisCommand::RAFT_LEADER_INFO: {
+      // safe, read-only request, does not need authorization
+      RaftStateSnapshotPtr snapshot = state.getSnapshot();
+      if(snapshot->status != RaftStatus::LEADER) {
+        if(snapshot->leader.empty()) {
+          return conn->err("unavailable");
+        }
+        return conn->moved(0, snapshot->leader);
+      }
+      return conn->statusVector(this->info().toVector());
+    }
     case RedisCommand::RAFT_FETCH_LAST: {
       // safe, read-only request, does not need authorization
       if(req.size() != 2 && req.size() != 3) return conn->errArgs(req[0]);