no-leaderless-notification

Signed-off-by: Michał Maślanka <[email protected]>

Author: mmaslankaprv

src/v/raft/consensus.cc

@@ -237,7 +237,6 @@ void consensus::maybe_step_down() {
                     do_step_down("heartbeats_majority");
                     if (_leader_id) {
                         _leader_id = std::nullopt;
-                        trigger_leadership_notification();
                     }
                 }
             }
@@ -1881,7 +1880,6 @@ ss::future<vote_reply> consensus::do_vote(vote_request r) {
         do_step_down("candidate_term_greater");
         if (_leader_id) {
             _leader_id = std::nullopt;
-            trigger_leadership_notification();
         }
 
         // do not grant vote if log isn't ok
@@ -3134,7 +3132,6 @@ ss::future<> consensus::maybe_commit_configuration(ssx::semaphore_units u) {
         co_await transfer_and_stepdown("no_longer_member");
         if (_leader_id) {
             _leader_id = std::nullopt;
-            trigger_leadership_notification();
         }
     }
 }
@@ -3664,7 +3661,6 @@ consensus::do_transfer_leadership(transfer_leadership_request req) {
                               do_step_down("leadership_transfer");
                               if (_leader_id) {
                                   _leader_id = std::nullopt;
-                                  trigger_leadership_notification();
                               }
 
                               return make_error_code(errc::success);

src/v/raft/consensus.h

@@ -359,7 +359,6 @@ class consensus {
             do_step_down(fmt::format("external_stepdown - {}", ctx));
             if (_leader_id) {
                 _leader_id = std::nullopt;
-                trigger_leadership_notification();
             }
         });
     }

src/v/raft/tests/basic_raft_fixture_test.cc

@@ -770,15 +770,15 @@ TEST_F_CORO(raft_fixture, leadership_transfer_delay) {
     auto leader_id = get_leader().value();
     auto& leader_node = node(leader_id);
     auto current_term = leader_node.raft()->term();
+    clock_t::time_point start = clock_t::now();
     auto r = co_await leader_node.raft()->transfer_leadership(
       transfer_leadership_request{.group = leader_node.raft()->group()});
     ASSERT_TRUE_CORO(r.success);
     // here we wait for all the replicas to notify about the leadership changes,
-    // each replica will notify two times, one when there is no leader, second
-    // time when the leader is elected. We have 4 replicas so in total we expect
-    // 8 notifications to be fired.
+    // each replica will notify one time only when the leader is elected. We
+    // have 4 replicas so in total we expect 4 notifications to be fired.
     co_await tests::cooperative_spin_wait_with_timeout(
-      10s, [&] { return events.size() >= 8; });
+      10s, [&] { return events.size() >= 4; });
 
     // calculate the time needed to transfer leadership, in our case it is the
     // time between first notification reporting no leader and first reporting
@@ -789,8 +789,7 @@ TEST_F_CORO(raft_fixture, leadership_transfer_delay) {
                  && ev.status.term > current_term;
       });
 
-    auto transfer_time = new_leader_reported_ev->timestamp
-                         - events.begin()->timestamp;
+    auto transfer_time = new_leader_reported_ev->timestamp - start;
     vlog(
       tstlog.info,
       "leadership_transfer - new leader reported after: {} ms",
@@ -806,10 +805,19 @@ TEST_F_CORO(raft_fixture, leadership_transfer_delay) {
     co_await new_leader_node.raft()->replace_configuration(
       std::vector<vnode>{new_nodes.begin(), new_nodes.end()},
       model::revision_id(2));
-    // analogically to the previous case we wait for 6 notifications as
+    // wait for no leader to be reported
+    co_await tests::cooperative_spin_wait_with_timeout(10s, [&] {
+        if (new_leader_node.raft()->get_leader_id() == std::nullopt) {
+            return true;
+        }
+        return new_leader_node.raft()->term() > current_term;
+    });
+
+    start = clock_t::now();
+    // analogically to the previous case we wait for 3 notifications as
     // currently the group has only 3 replicas
     co_await tests::cooperative_spin_wait_with_timeout(
-      10s, [&] { return events.size() >= 6; });
+      10s, [&] { return events.size() >= 3; });
 
     auto leader_reported_after_reconfiguration = std::find_if(
       events.begin(), events.end(), [&](leadership_changed_event& ev) {
@@ -818,7 +826,7 @@ TEST_F_CORO(raft_fixture, leadership_transfer_delay) {
       });
 
     auto election_time = leader_reported_after_reconfiguration->timestamp
-                         - events.begin()->timestamp;
+                         - start;
     vlog(
       tstlog.info,
       "reconfiguration - new leader reported after: {} ms",
@@ -834,7 +842,6 @@ TEST_F_CORO(raft_fixture, leadership_transfer_delay) {
      * time needed for leadership transfer
      */
     ASSERT_LE_CORO(election_time * 1.0, transfer_time * tolerance_multiplier);
-    ASSERT_GE_CORO(election_time * 1.0, transfer_time / tolerance_multiplier);
 }
 
 TEST_F_CORO(raft_fixture, test_no_stepdown_on_append_entries_timeout) {

src/v/raft/vote_stm.cc

@@ -140,7 +140,6 @@ ss::future<election_success> vote_stm::vote(bool leadership_transfer) {
               //  only trigger notification when we had a leader previously
               if (_ptr->_leader_id) {
                   _ptr->_leader_id = std::nullopt;
-                  _ptr->trigger_leadership_notification();
               }
 
               if (_prevote && leadership_transfer) {