Constrained successor and destination block activation (#2895)

* Activations only on active_confirmed_quorum or active_confirmation_height

* Only activate after cementing hardcoded bootstrap block count

* Limit activation of successor/destination elections

* Lazily evaluate one of the conditions

nano/core_test/active_transactions.cpp

@@ -1372,3 +1372,65 @@ TEST (active_transactions, activate_account_chain)
 	ASSERT_TIMELY (3s, node.block_confirmed (send3->hash ()));
 	ASSERT_TIMELY (3s, node.active.active (receive->qualified_root ()));
 }
+
+TEST (active_transactions, activate_inactive)
+{
+	nano::system system;
+	nano::node_flags flags;
+	nano::node_config config (nano::get_available_port (), system.logging);
+	config.frontiers_confirmation = nano::frontiers_confirmation_mode::disabled;
+	auto & node = *system.add_node (config, flags);
+
+	nano::keypair key;
+	nano::state_block_builder builder;
+	auto send = builder.make_block ()
+	            .account (nano::dev_genesis_key.pub)
+	            .previous (nano::genesis_hash)
+	            .representative (nano::dev_genesis_key.pub)
+	            .link (key.pub)
+	            .balance (nano::genesis_amount - 1)
+	            .sign (nano::dev_genesis_key.prv, nano::dev_genesis_key.pub)
+	            .work (*system.work.generate (nano::genesis_hash))
+	            .build_shared ();
+	auto send2 = builder.make_block ()
+	             .account (nano::dev_genesis_key.pub)
+	             .previous (send->hash ())
+	             .representative (nano::dev_genesis_key.pub)
+	             .link (nano::keypair ().pub)
+	             .balance (nano::genesis_amount - 2)
+	             .sign (nano::dev_genesis_key.prv, nano::dev_genesis_key.pub)
+	             .work (*system.work.generate (send->hash ()))
+	             .build_shared ();
+	auto open = builder.make_block ()
+	            .account (key.pub)
+	            .previous (0)
+	            .representative (key.pub)
+	            .link (send->hash ())
+	            .balance (1)
+	            .sign (key.prv, key.pub)
+	            .work (*system.work.generate (key.pub))
+	            .build_shared ();
+
+	ASSERT_EQ (nano::process_result::progress, node.process (*send).code);
+	ASSERT_EQ (nano::process_result::progress, node.process (*send2).code);
+	ASSERT_EQ (nano::process_result::progress, node.process (*open).code);
+
+	node.block_confirm (send2);
+	{
+		auto election = node.active.election (send2->qualified_root ());
+		ASSERT_NE (nullptr, election);
+		nano::lock_guard<std::mutex> guard (node.active.mutex);
+		election->confirm_once ();
+	}
+
+	ASSERT_TIMELY (3s, !node.confirmation_height_processor.is_processing_added_block (send2->hash ()));
+	ASSERT_TRUE (node.block_confirmed (send2->hash ()));
+	ASSERT_TRUE (node.block_confirmed (send->hash ()));
+
+	ASSERT_EQ (1, node.stats.count (nano::stat::type::confirmation_observer, nano::stat::detail::inactive_conf_height, nano::stat::dir::out));
+	ASSERT_EQ (1, node.stats.count (nano::stat::type::confirmation_observer, nano::stat::detail::active_quorum, nano::stat::dir::out));
+	ASSERT_EQ (0, node.stats.count (nano::stat::type::confirmation_observer, nano::stat::detail::active_conf_height, nano::stat::dir::out));
+
+	// The first block was not active so no activation takes place
+	ASSERT_FALSE (node.active.active (open->qualified_root ()) || node.block_confirmed_or_being_confirmed (node.store.tx_begin_read (), open->hash ()));
+}

nano/core_test/confirmation_height.cpp

@@ -348,16 +348,13 @@ TEST (confirmation_height, gap_live)
 			ASSERT_EQ (nano::genesis_hash, confirmation_height_info.frontier);
 		}
 
+		// Vote and confirm all existing blocks
+		node->block_confirm (send1);
+		ASSERT_TIMELY (10s, node->stats.count (nano::stat::type::http_callback, nano::stat::detail::http_callback, nano::stat::dir::out) == 3);
+
 		// Now complete the chain where the block comes in on the live network
 		node->process_active (open1);
 		node->block_processor.flush ();
-		node->block_confirm (open1);
-		{
-			auto election = node->active.election (open1->qualified_root ());
-			ASSERT_NE (nullptr, election);
-			nano::lock_guard<std::mutex> guard (node->active.mutex);
-			election->confirm_once ();
-		}
 
 		ASSERT_TIMELY (10s, node->stats.count (nano::stat::type::http_callback, nano::stat::detail::http_callback, nano::stat::dir::out) == 6);
 

nano/node/active_transactions.cpp

@@ -14,6 +14,8 @@
 
 using namespace std::chrono;
 
+size_t constexpr nano::active_transactions::max_active_elections_frontier_insertion;
+
 nano::active_transactions::active_transactions (nano::node & node_a, nano::confirmation_height_processor & confirmation_height_processor_a) :
 recently_dropped (node_a.stats),
 confirmation_height_processor (confirmation_height_processor_a),
@@ -59,7 +61,7 @@ void nano::active_transactions::confirm_prioritized_frontiers (nano::transaction
 	auto is_dev_network = node.network_params.network.is_dev_network ();
 	auto roots_size = size ();
 	auto check_time_exceeded = std::chrono::steady_clock::now () >= next_frontier_check;
-	auto max_elections = 1000ull;
+	auto max_elections = max_active_elections_frontier_insertion;
 	auto low_active_elections = roots_size < max_elections;
 	bool wallets_check_required = (!skip_wallets || !priority_wallet_cementable_frontiers.empty ()) && !agressive_mode;
 	// Minimise dropping real-time transactions, set the number of frontiers added to a factor of the maximum number of possible active elections
@@ -189,16 +191,29 @@ void nano::active_transactions::block_cemented_callback (std::shared_ptr<nano::b
 			}
 		}
 
-		// Start or vote for the next unconfirmed block in this account
 		auto const & account (!block_a->account ().is_zero () ? block_a->account () : block_a->sideband ().account);
 		debug_assert (!account.is_zero ());
-		activate (account);
 
-		// Start or vote for the next unconfirmed block in the destination account
-		auto const & destination (node.ledger.block_destination (transaction, *block_a));
-		if (!destination.is_zero () && destination != account)
+		// Next-block activations are done after cementing hardcoded bootstrap count to allow confirming very large chains without interference
+		bool const cemented_bootstrap_count_reached{ node.ledger.cache.cemented_count >= node.ledger.bootstrap_weight_max_blocks };
+
+		// Next-block activations are only done for blocks with previously active elections
+		bool const was_active{ *election_status_type == nano::election_status_type::active_confirmed_quorum || *election_status_type == nano::election_status_type::active_confirmation_height };
+
+		// Activations are only done if there is not a large amount of active elections, ensuring frontier confirmation takes place
+		auto const low_active_elections = [this] { return this->size () < nano::active_transactions::max_active_elections_frontier_insertion / 2; };
+
+		if (cemented_bootstrap_count_reached && was_active && low_active_elections ())
 		{
-			activate (destination);
+			// Start or vote for the next unconfirmed block
+			activate (account);
+
+			// Start or vote for the next unconfirmed block in the destination account
+			auto const & destination (node.ledger.block_destination (transaction, *block_a));
+			if (!destination.is_zero () && destination != account)
+			{
+				activate (destination);
+			}
 		}
 	}
 }

nano/node/active_transactions.hpp

@@ -226,6 +226,7 @@ private:
 	void frontiers_confirmation (nano::unique_lock<std::mutex> &);
 	nano::account next_frontier_account{ 0 };
 	std::chrono::steady_clock::time_point next_frontier_check{ std::chrono::steady_clock::now () };
+	constexpr static size_t max_active_elections_frontier_insertion{ 1000 };
 	nano::condition_variable condition;
 	bool started{ false };
 	std::atomic<bool> stopped{ false };

nano/node/node.cpp

@@ -411,13 +411,13 @@ node_seq (seq)
 			bool use_bootstrap_weight = ledger.cache.block_count < bootstrap_weights.first;
 			if (use_bootstrap_weight)
 			{
-				ledger.bootstrap_weight_max_blocks = bootstrap_weights.first;
 				ledger.bootstrap_weights = bootstrap_weights.second;
 				for (auto const & rep : ledger.bootstrap_weights)
 				{
 					logger.always_log ("Using bootstrap rep weight: ", rep.first.to_account (), " -> ", nano::uint128_union (rep.second).format_balance (Mxrb_ratio, 0, true), " XRB");
 				}
 			}
+			ledger.bootstrap_weight_max_blocks = bootstrap_weights.first;
 
 			// Drop unchecked blocks if initial bootstrap is completed
 			if (!flags.disable_unchecked_drop && !use_bootstrap_weight && !flags.read_only)