cluster: store number of leaders per node in _topic_node_index

src/v/cluster/scheduling/leader_balancer_constraints.cc

@@ -42,20 +42,8 @@ void even_topic_distributon_constraint::update_index(const reassignment& r) {
     _error += skew;
 
     // Update _topic_node_index
-
-    auto& groups_from_node = _topic_node_index.at(topic_id).at(r.from.node_id);
-    auto it = std::find_if(
-      groups_from_node.begin(),
-      groups_from_node.end(),
-      [&r](const auto& g_info) { return r.group == g_info.group_id; });
-
-    vassert(it != groups_from_node.end(), "reassigning non-existent group");
-
-    auto moved_group_info = std::move(*it);
-    groups_from_node.erase(it);
-
-    _topic_node_index[topic_id][r.to.node_id].emplace_back(
-      moved_group_info.group_id, r.to, std::move(moved_group_info.replicas));
+    _topic_node_index.at(topic_id).at(r.from.node_id) -= 1;
+    _topic_node_index.at(topic_id).at(r.to.node_id) += 1;
 
     // Update _si
 
@@ -81,8 +69,7 @@ void even_topic_distributon_constraint::rebuild_indexes() {
             auto topic_id = group_to_topic_id().at(group_p.first);
             const auto& node_id = broker_shard.first.node_id;
 
-            _topic_node_index[topic_id][node_id].emplace_back(
-              group_p.first, broker_shard.first, group_p.second);
+            _topic_node_index[topic_id][node_id] += 1;
             _topic_partition_index[topic_id] += 1;
 
             // Some of the replicas may not have leadership. So add
@@ -125,7 +112,7 @@ void even_topic_distributon_constraint::calc_topic_skew() {
         skew = 0;
 
         for (const auto& node : topic.second) {
-            auto leaders = static_cast<double>(node.second.size());
+            auto leaders = static_cast<double>(node.second);
 
             skew += pow(leaders - opt_leaders, 2);
         }
@@ -153,7 +140,7 @@ double even_topic_distributon_constraint::adjusted_error(
     double from_node_leaders = 0;
     const auto from_it = topic_leaders.find(from.node_id);
     if (from_it != topic_leaders.cend()) {
-        from_node_leaders = static_cast<double>(from_it->second.size());
+        from_node_leaders = static_cast<double>(from_it->second);
     } else {
         // If there are no leaders for the topic on the from node
         // then there is nothing to move and no change to the error.
@@ -163,7 +150,7 @@ double even_topic_distributon_constraint::adjusted_error(
     double to_node_leaders = 0;
     const auto to_it = topic_leaders.find(to.node_id);
     if (to_it != topic_leaders.cend()) {
-        to_node_leaders = static_cast<double>(to_it->second.size());
+        to_node_leaders = static_cast<double>(to_it->second);
     }
 
     // Subtract old weights

src/v/cluster/scheduling/leader_balancer_constraints.h

@@ -107,20 +107,6 @@ class even_topic_distributon_constraint final
     // more than this value.
     static constexpr double error_jitter = 0.000001;
 
-    struct group_info {
-        raft::group_id group_id;
-        model::broker_shard leader;
-        std::vector<model::broker_shard> replicas;
-
-        group_info(
-          const raft::group_id& gid,
-          const model::broker_shard& bs,
-          std::vector<model::broker_shard> r)
-          : group_id(gid)
-          , leader(bs)
-          , replicas(std::move(r)) {}
-    };
-
     using topic_id_t = model::revision_id::type;
 
     template<typename ValueType>
@@ -171,8 +157,8 @@ class even_topic_distributon_constraint final
     group_id_to_topic_revision_t _group_to_topic_rev;
     double _error{0};
 
-    topic_map<absl::flat_hash_map<model::node_id, std::vector<group_info>>>
-      _topic_node_index;
+    // Stores the number of leaders on a given node per topic.
+    topic_map<absl::flat_hash_map<model::node_id, size_t>> _topic_node_index;
     topic_map<size_t> _topic_partition_index;
     topic_map<absl::flat_hash_set<model::node_id>> _topic_replica_index;
     topic_map<double> _topic_skew;