Make election behavior mutable to support dynamic behaviour transition

nano/core_test/election_scheduler.cpp

@@ -4,6 +4,7 @@
 #include <nano/node/scheduler/component.hpp>
 #include <nano/node/scheduler/priority.hpp>
 #include <nano/secure/ledger.hpp>
+#include <nano/test_common/chains.hpp>
 #include <nano/test_common/system.hpp>
 #include <nano/test_common/testutil.hpp>
 
@@ -157,6 +158,57 @@ TEST (election_scheduler, activate_one_flush)
 	ASSERT_TIMELY (5s, node.active.election (send1->qualified_root ()));
 }
 
+/*
+ * Tests that an optimistic election can be transitioned to a priority election.
+ *
+ * The test:
+ * 1. Creates a chain of 2 blocks with an optimistic election for the second block
+ * 2. Confirms the first block in the chain
+ * 3. Attempts to start a priority election for the second block
+ * 4. Verifies that the existing optimistic election is transitioned to priority
+ * 5. Verifies a new vote is broadcast after the transition
+ */
+TEST (election_scheduler, transition_optimistic_to_priority)
+{
+	nano::test::system system;
+	nano::node_config config = system.default_config ();
+	config.optimistic_scheduler.gap_threshold = 1;
+	config.enable_voting = true;
+	config.hinted_scheduler.enable = false;
+	config.network_params.network.vote_broadcast_interval = 15000ms;
+	auto & node = *system.add_node (config);
+
+	// Add representative
+	const nano::uint128_t rep_weight = nano::Knano_ratio * 100;
+	nano::keypair rep = nano::test::setup_rep (system, node, rep_weight);
+	system.wallet (0)->insert_adhoc (rep.prv);
+
+	// Create a chain of blocks - and trigger an optimistic election for the last block
+	const int howmany_blocks = 2;
+	auto chains = nano::test::setup_chains (system, node, /* single chain */ 1, howmany_blocks, nano::dev::genesis_key, /* do not confirm */ false);
+	auto & [account, blocks] = chains.front ();
+
+	// Wait for optimistic election to start for last block
+	auto const & block = blocks.back ();
+	ASSERT_TIMELY (5s, node.vote_router.active (block->hash ()));
+	auto election = node.active.election (block->qualified_root ());
+	ASSERT_EQ (election->behavior (), nano::election_behavior::optimistic);
+	ASSERT_TIMELY_EQ (1s, 1, election->current_status ().status.vote_broadcast_count);
+
+	// Confirm first block to allow upgrading second block's election
+	nano::test::confirm (node.ledger, blocks.at (howmany_blocks - 1));
+
+	// Attempt to start priority election for second block
+	node.active.insert (block, nano::election_behavior::priority);
+
+	// Verify priority transition
+	ASSERT_EQ (election->behavior (), nano::election_behavior::priority);
+	ASSERT_EQ (1, node.stats.count (nano::stat::type::active_elections, nano::stat::detail::transition_priority));
+	// Verify vote broadcast after transitioning
+	ASSERT_TIMELY_EQ (1s, 2, election->current_status ().status.vote_broadcast_count);
+	ASSERT_TRUE (node.active.active (*block));
+}
+
 /**
  * Tests that the election scheduler and the active transactions container (AEC)
  * work in sync with regards to the node configuration value "active_elections.size".

nano/lib/stats_enums.hpp

@@ -426,6 +426,8 @@ enum class detail
 	// active
 	insert,
 	insert_failed,
+	transition_priority,
+	transition_priority_failed,
 	election_cleanup,
 
 	// active_elections

nano/node/active_elections.cpp

@@ -435,6 +435,23 @@ nano::election_insertion_result nano::active_elections::insert (std::shared_ptr<
 	else
 	{
 		result.election = existing->election;
+
+		// Upgrade to priority election to enable immediate vote broadcasting.
+		auto previous_behavior = result.election->behavior ();
+		if (election_behavior_a == nano::election_behavior::priority && previous_behavior != nano::election_behavior::priority)
+		{
+			bool transitioned = result.election->transition_priority ();
+			if (transitioned)
+			{
+				count_by_behavior[previous_behavior]--;
+				count_by_behavior[election_behavior_a]++;
+				node.stats.inc (nano::stat::type::active_elections, nano::stat::detail::transition_priority);
+			}
+			else
+			{
+				node.stats.inc (nano::stat::type::active_elections, nano::stat::detail::transition_priority_failed);
+			}
+		}
 	}
 
 	lock.unlock ();

nano/node/election.cpp

@@ -27,7 +27,7 @@ nano::election::election (nano::node & node_a, std::shared_ptr<nano::block> cons
 	live_vote_action (live_vote_action_a),
 	node (node_a),
 	behavior_m (election_behavior_a),
-	status ({ block_a, 0, 0, std::chrono::duration_cast<std::chrono::milliseconds> (std::chrono::system_clock::now ().time_since_epoch ()), std::chrono::duration_values<std::chrono::milliseconds>::zero (), 0, 1, 0, nano::election_status_type::ongoing }),
+	status (block_a),
 	height (block_a->sideband ().height),
 	root (block_a->root ()),
 	qualified_root (block_a->qualified_root ())
@@ -152,7 +152,7 @@ bool nano::election::state_change (nano::election_state expected_a, nano::electi
 
 std::chrono::milliseconds nano::election::confirm_req_time () const
 {
-	switch (behavior ())
+	switch (behavior_m)
 	{
 		case election_behavior::manual:
 		case election_behavior::priority:
@@ -183,6 +183,25 @@ void nano::election::transition_active ()
 	state_change (nano::election_state::passive, nano::election_state::active);
 }
 
+bool nano::election::transition_priority ()
+{
+	nano::lock_guard<nano::mutex> guard{ mutex };
+
+	if (behavior_m == nano::election_behavior::priority || behavior_m == nano::election_behavior::manual)
+	{
+		return false;
+	}
+
+	behavior_m = nano::election_behavior::priority;
+	last_vote = std::chrono::steady_clock::time_point{}; // allow new outgoing votes immediately
+
+	node.logger.debug (nano::log::type::election, "Transitioned election behavior to priority from {} for root: {}",
+	to_string (behavior_m),
+	qualified_root.to_string ());
+
+	return true;
+}
+
 void nano::election::cancel ()
 {
 	nano::lock_guard<nano::mutex> guard{ mutex };
@@ -314,7 +333,7 @@ bool nano::election::transition_time (nano::confirmation_solicitor & solicitor_a
 
 std::chrono::milliseconds nano::election::time_to_live () const
 {
-	switch (behavior ())
+	switch (behavior_m)
 	{
 		case election_behavior::manual:
 		case election_behavior::priority:
@@ -421,6 +440,7 @@ void nano::election::confirm_if_quorum (nano::unique_lock<nano::mutex> & lock_a)
 	{
 		if (!is_quorum.exchange (true) && node.config.enable_voting && node.wallets.reps ().voting > 0)
 		{
+			++vote_broadcast_count;
 			node.final_generator.add (root, status.winner->hash ());
 		}
 		if (final_weight >= node.online_reps.delta ())
@@ -577,6 +597,7 @@ nano::election_extended_status nano::election::current_status_locked () const
 
 	nano::election_status status_l = status;
 	status_l.confirmation_request_count = confirmation_request_count;
+	status_l.vote_broadcast_count = vote_broadcast_count;
 	status_l.block_count = nano::narrow_cast<decltype (status_l.block_count)> (last_blocks.size ());
 	status_l.voter_count = nano::narrow_cast<decltype (status_l.voter_count)> (last_votes.size ());
 	return nano::election_extended_status{ status_l, last_votes, last_blocks, tally_impl () };
@@ -606,6 +627,7 @@ void nano::election::broadcast_vote_locked (nano::unique_lock<nano::mutex> & loc
 	if (node.config.enable_voting && node.wallets.reps ().voting > 0)
 	{
 		node.stats.inc (nano::stat::type::election, nano::stat::detail::broadcast_vote);
+		++vote_broadcast_count;
 
 		if (confirmed_locked () || have_quorum (tally_impl ()))
 		{
@@ -771,6 +793,7 @@ std::vector<nano::vote_with_weight_info> nano::election::votes_with_weight () co
 
 nano::election_behavior nano::election::behavior () const
 {
+	nano::lock_guard<nano::mutex> guard{ mutex };
 	return behavior_m;
 }
 
@@ -802,6 +825,7 @@ void nano::election_extended_status::operator() (nano::object_stream & obs) cons
 	obs.write ("tally_amount", status.tally.to_string_dec ());
 	obs.write ("final_tally_amount", status.final_tally.to_string_dec ());
 	obs.write ("confirmation_request_count", status.confirmation_request_count);
+	obs.write ("vote_broadcast_count", status.vote_broadcast_count);
 	obs.write ("block_count", status.block_count);
 	obs.write ("voter_count", status.voter_count);
 	obs.write ("type", status.type);

nano/node/election.hpp

@@ -87,6 +87,7 @@ class election final : public std::enable_shared_from_this<election>
 public: // State transitions
 	bool transition_time (nano::confirmation_solicitor &);
 	void transition_active ();
+	bool transition_priority ();
 	void cancel ();
 
 public: // Status
@@ -96,6 +97,7 @@ class election final : public std::enable_shared_from_this<election>
 	std::shared_ptr<nano::block> winner () const;
 	std::chrono::milliseconds duration () const;
 	std::atomic<unsigned> confirmation_request_count{ 0 };
+	std::atomic<unsigned> vote_broadcast_count{ 0 };
 
 	nano::tally_t tally () const;
 	bool have_quorum (nano::tally_t const &) const;
@@ -180,7 +182,7 @@ class election final : public std::enable_shared_from_this<election>
 	mutable nano::uint128_t final_weight{ 0 };
 	mutable std::unordered_map<nano::block_hash, nano::uint128_t> last_tally;
 
-	nano::election_behavior const behavior_m;
+	nano::election_behavior behavior_m;
 	std::chrono::steady_clock::time_point const election_start{ std::chrono::steady_clock::now () };
 
 	mutable nano::mutex mutex;

nano/node/election_status.hpp

@@ -35,8 +35,18 @@ class election_status final
 	std::chrono::milliseconds election_end{ std::chrono::duration_cast<std::chrono::milliseconds> (std::chrono::system_clock::now ().time_since_epoch ()) };
 	std::chrono::milliseconds election_duration{ std::chrono::duration_values<std::chrono::milliseconds>::zero () };
 	unsigned confirmation_request_count{ 0 };
+	unsigned vote_broadcast_count{ 0 };
 	unsigned block_count{ 0 };
 	unsigned voter_count{ 0 };
 	election_status_type type{ nano::election_status_type::inactive_confirmation_height };
+
+	election_status () = default;
+
+	election_status (std::shared_ptr<nano::block> block_a, election_status_type type_a = nano::election_status_type::ongoing) :
+		winner (block_a),
+		type (type_a)
+	{
+		block_count = 1;
+	}
 };
 }

nano/node/json_handler.cpp

@@ -1196,7 +1196,7 @@ void nano::json_handler::block_confirm ()
 			else
 			{
 				// Add record in confirmation history for confirmed block
-				nano::election_status status{ block_l, 0, 0, std::chrono::duration_cast<std::chrono::milliseconds> (std::chrono::system_clock::now ().time_since_epoch ()), std::chrono::duration_values<std::chrono::milliseconds>::zero (), 0, 1, 0, nano::election_status_type::active_confirmation_height };
+				nano::election_status status{ block_l, nano::election_status_type::active_confirmation_height };
 				node.active.recently_cemented.put (status);
 				// Trigger callback for confirmed block
 				auto account = block_l->account ();