Currently there is no rate limiter on vote generation for a particula…

…r root and this can lead to increased, unnecessary vote traffic.

This patch adds a delay between constructing non-cached votes.

nano/core_test/voting.cpp

@@ -118,3 +118,46 @@ TEST (vote_generator, session)
 	thread.join ();
 	ASSERT_TIMELY (2s, 1 == node->stats.count (nano::stat::type::vote, nano::stat::detail::vote_indeterminate));
 }
+
+namespace nano {
+TEST (vote_generator, vote_spacing)
+{
+	nano::node_config config;
+	config.frontiers_confirmation = nano::frontiers_confirmation_mode::disabled;
+	nano::system system;
+	auto & node = *system.add_node (config);
+	auto & wallet = *system.wallet (0);
+	wallet.insert_adhoc (nano::dev_genesis_key.prv);
+	nano::state_block_builder builder;
+	auto send1 = builder.make_block ()
+	             .account (nano::dev_genesis_key.pub)
+	             .previous (nano::genesis_hash)
+	              .representative (nano::dev_genesis_key.pub)
+	             .balance (nano::genesis_amount - nano::Gxrb_ratio)
+	             .link (nano::dev_genesis_key.pub)
+	             .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 (nano::genesis_hash)
+	             .representative (nano::dev_genesis_key.pub)
+	             .balance (nano::genesis_amount - nano::Gxrb_ratio - 1)
+	             .link (nano::dev_genesis_key.pub)
+	             .sign (nano::dev_genesis_key.prv, nano::dev_genesis_key.pub)
+	             .work (*system.work.generate (nano::genesis_hash))
+	             .build_shared ();
+	ASSERT_EQ (nano::process_result::progress, node.ledger.process (node.store.tx_begin_write (), *send1).code);
+	ASSERT_EQ (0, node.stats.count (nano::stat::type::vote_generator, nano::stat::detail::generator_broadcasts));
+	node.active.generator.add (nano::genesis_hash, send1->hash ());
+	ASSERT_TIMELY (3s, node.stats.count (nano::stat::type::vote_generator, nano::stat::detail::generator_broadcasts) == 1);
+	ASSERT_FALSE (node.ledger.rollback (node.store.tx_begin_write (), send1->hash ()));
+	ASSERT_EQ (nano::process_result::progress, node.ledger.process (node.store.tx_begin_write (), *send2).code);
+	node.active.generator.add (nano::genesis_hash, send2->hash ());
+	ASSERT_TIMELY (3s, node.stats.count (nano::stat::type::vote_generator, nano::stat::detail::generator_spacing) == 1);
+	ASSERT_EQ (1, node.stats.count (nano::stat::type::vote_generator, nano::stat::detail::generator_broadcasts));
+	std::this_thread::sleep_for (node.active.generator.history.delay);
+	node.active.generator.add (nano::genesis_hash, send2->hash ());
+	ASSERT_TIMELY (3s, node.stats.count (nano::stat::type::vote_generator, nano::stat::detail::generator_broadcasts) == 2);
+}
+}

nano/lib/stats.cpp

@@ -760,6 +760,9 @@ std::string nano::stat::detail_to_string (uint32_t key)
 		case nano::stat::detail::generator_replies_discarded:
 			res = "generator_replies_discarded";
 			break;
+		case nano::stat::detail::generator_spacing:
+			res = "generator_spacing";
+			break;
 	}
 	return res;
 }

nano/lib/stats.hpp

@@ -342,7 +342,8 @@ class stat final
 		// vote generator
 		generator_broadcasts,
 		generator_replies,
-		generator_replies_discarded
+		generator_replies_discarded,
+		generator_spacing
 	};
 
 	/** Direction of the stat. If the direction is irrelevant, use in */

nano/node/voting.cpp

@@ -101,6 +101,17 @@ size_t nano::local_vote_history::size () const
 	return history.size ();
 }
 
+bool nano::local_vote_history::votable (nano::root const & root_a, nano::block_hash const & hash_a) const
+{
+	bool result = true;
+	for (auto range = history.get<tag_root> ().equal_range (root_a); result && range.first != range.second; ++range.first)
+	{
+		auto & item = *range.first;
+		result = item.time < std::chrono::steady_clock::now () - delay || item.hash == hash_a;
+	}
+	return result;
+}
+
 std::unique_ptr<nano::container_info_component> nano::collect_container_info (nano::local_vote_history & history, const std::string & name)
 {
 	size_t history_count = history.size ();
@@ -219,18 +230,27 @@ void nano::vote_generator::broadcast (nano::unique_lock<std::mutex> & lock_a)
 		}
 		if (cached_votes.empty ())
 		{
-			roots.push_back (root);
-			hashes.push_back (hash);
+			if (history.votable (root, hash))
+			{
+				roots.push_back (root);
+				hashes.push_back (hash);
+			}
+			else
+			{
+				stats.inc (nano::stat::type::vote_generator, nano::stat::detail::generator_spacing);
+			}
 		}
 		candidates.pop_front ();
 	}
 	if (!hashes.empty ())
 	{
 		lock_a.unlock ();
-		vote (hashes, roots, [this](auto const & vote_a) { this->broadcast_action (vote_a); });
+		vote (hashes, roots, [this](auto const & vote_a) {
+			this->broadcast_action (vote_a);
+			this->stats.inc (nano::stat::type::vote_generator, nano::stat::detail::generator_broadcasts);
+		});
 		lock_a.lock ();
 	}
-	stats.inc (nano::stat::type::vote_generator, nano::stat::detail::generator_broadcasts);
 }
 
 void nano::vote_generator::reply (nano::unique_lock<std::mutex> & lock_a, request_t && request_a)

nano/node/voting.hpp

@@ -45,6 +45,7 @@ class local_vote_history final
 		}
 		nano::root root;
 		nano::block_hash hash;
+		std::chrono::steady_clock::time_point time{ std::chrono::steady_clock::now () };
 		std::shared_ptr<nano::vote> vote;
 	};
 
@@ -55,6 +56,7 @@ class local_vote_history final
 	std::vector<std::shared_ptr<nano::vote>> votes (nano::root const & root_a, nano::block_hash const & hash_a) const;
 	bool exists (nano::root const &) const;
 	size_t size () const;
+	bool votable (nano::root const & root_a, nano::block_hash const & hash_a) const;
 
 private:
 	// clang-format off
@@ -72,10 +74,11 @@ class local_vote_history final
 	// Only used in Debug
 	bool consistency_check (nano::root const &) const;
 	mutable std::mutex mutex;
+	std::chrono::seconds const delay{ nano::network_params ().network.is_dev_network () ? 1 : 15 };
 
 	friend std::unique_ptr<container_info_component> collect_container_info (local_vote_history & history, const std::string & name);
-
 	friend class local_vote_history_basic_Test;
+	friend class vote_generator_vote_spacing_Test;
 };
 
 std::unique_ptr<container_info_component> collect_container_info (local_vote_history & history, const std::string & name);
@@ -120,6 +123,7 @@ class vote_generator final
 	bool started{ false };
 	std::thread thread;
 
+	friend class vote_generator_vote_spacing_Test;
 	friend std::unique_ptr<container_info_component> collect_container_info (vote_generator & vote_generator, const std::string & name);
 };