[fix] arbitration_service prints WDIAG logs when there is no arb member

src/logservice/palf/log_meta_info.cpp

@@ -426,8 +426,9 @@ int LogConfigInfo::get_expected_paxos_memberlist(common::ObMemberList &paxos_mem
   if (false == log_sync_memberlist_.is_valid() ||
       0 >= log_sync_replica_num_ ||
       common::OB_MAX_MEMBER_NUMBER < log_sync_replica_num_) {
-    ret = OB_NOT_INIT;
-    PALF_LOG(WARN, "LogConfigInfo not init", KR(ret), K_(log_sync_memberlist), K_(log_sync_replica_num));
+    // memberlist may be empty when bootstraping cluster, just return empty memberlist
+    paxos_memberlist.reset();
+    paxos_replica_num = 0;
   } else if (OB_UNLIKELY(degraded_learnerlist_.is_valid())) {
     paxos_memberlist = log_sync_memberlist_;
     paxos_replica_num = log_sync_replica_num_;

src/logservice/palf/palf_handle_impl.cpp

@@ -3715,6 +3715,7 @@ int PalfHandleImpl::inner_flashback(const share::SCN &flashback_scn)
   return ret;
 }
 
+// TODO by yunlong: this function needs refactoring in 4.2.0.0
 int PalfHandleImpl::get_ack_info_array(LogMemberAckInfoList &ack_info_array,
                                        common::GlobalLearnerList &degraded_list) const
 {
@@ -3722,11 +3723,16 @@ int PalfHandleImpl::get_ack_info_array(LogMemberAckInfoList &ack_info_array,
   RLockGuard guard(lock_);
   const bool is_leader = (state_mgr_.is_leader_active() ||
       (state_mgr_.is_leader_reconfirm() && reconfirm_.can_do_degrade()));
+  common::ObMember arb_member;
+  config_mgr_.get_arbitration_member(arb_member);
+  const bool need_degrade_or_upgrade = arb_member.is_valid();
   if (IS_NOT_INIT) {
     ret = OB_NOT_INIT;
     PALF_LOG(WARN, "PalfHandleImpl not inited!!!", K(ret));
   } else if (false == is_leader) {
     ret = OB_NOT_MASTER;
+  } else if (false == need_degrade_or_upgrade) {
+    // do not need degrade or upgrade, skip
   } else if (OB_FAIL(sw_.get_ack_info_array(ack_info_array))) {
     PALF_LOG(WARN, "get_ack_info_array failed", K(ret), KPC(this));
   } else if (OB_FAIL(config_mgr_.get_degraded_learner_list(degraded_list))) {