Add config option for vote hinting limit

nano/core_test/toml.cpp

@@ -148,6 +148,7 @@ TEST (toml, daemon_config_deserialize_defaults)
 	ASSERT_EQ (conf.rpc.child_process.rpc_path, defaults.rpc.child_process.rpc_path);
 
 	ASSERT_EQ (conf.node.active_elections_size, defaults.node.active_elections_size);
+	ASSERT_EQ (conf.node.active_elections_hinted_limit, defaults.node.active_elections_hinted_limit);
 	ASSERT_EQ (conf.node.allow_local_peers, defaults.node.allow_local_peers);
 	ASSERT_EQ (conf.node.backup_before_upgrade, defaults.node.backup_before_upgrade);
 	ASSERT_EQ (conf.node.bandwidth_limit, defaults.node.bandwidth_limit);
@@ -388,6 +389,7 @@ TEST (toml, daemon_config_deserialize_no_defaults)
 	ss << R"toml(
 	[node]
 	active_elections_size = 999
+	active_elections_hinted_limit = 999
 	allow_local_peers = false
 	backup_before_upgrade = true
 	bandwidth_limit = 999
@@ -552,6 +554,7 @@ TEST (toml, daemon_config_deserialize_no_defaults)
 	ASSERT_NE (conf.rpc.child_process.rpc_path, defaults.rpc.child_process.rpc_path);
 
 	ASSERT_NE (conf.node.active_elections_size, defaults.node.active_elections_size);
+	ASSERT_NE (conf.node.active_elections_hinted_limit, defaults.node.active_elections_hinted_limit);
 	ASSERT_NE (conf.node.allow_local_peers, defaults.node.allow_local_peers);
 	ASSERT_NE (conf.node.backup_before_upgrade, defaults.node.backup_before_upgrade);
 	ASSERT_NE (conf.node.bandwidth_limit, defaults.node.bandwidth_limit);

nano/node/nodeconfig.cpp

@@ -105,6 +105,7 @@ nano::error nano::node_config::serialize_toml (nano::tomlconfig & toml) const
 	toml.put ("use_memory_pools", use_memory_pools, "If true, allocate memory from memory pools. Enabling this may improve performance. Memory is never released to the OS.\ntype:bool");
 	toml.put ("confirmation_history_size", confirmation_history_size, "Maximum confirmation history size. If tracking the rate of block confirmations, the websocket feature is recommended instead.\ntype:uint64");
 	toml.put ("active_elections_size", active_elections_size, "Number of active elections. Elections beyond this limit have limited survival time.\nWarning: modifying this value may result in a lower confirmation rate.\ntype:uint64,[250..]");
+	toml.put ("active_elections_hinted_limit", active_elections_hinted_limit, "Limit of active hinted elections. No more hinted elections will be started beyond this limit.\nWarning: modifying this value may result in a lower confirmation rate.\ntype:uint64");
 	toml.put ("bandwidth_limit", bandwidth_limit, "Outbound traffic limit in bytes/sec after which messages will be dropped.\nNote: changing to unlimited bandwidth (0) is not recommended for limited connections.\ntype:uint64");
 	toml.put ("bandwidth_limit_burst_ratio", bandwidth_limit_burst_ratio, "Burst ratio for outbound traffic shaping.\ntype:double");
 	toml.put ("conf_height_processor_batch_min_time", conf_height_processor_batch_min_time.count (), "Minimum write batching time when there are blocks pending confirmation height.\ntype:milliseconds");
@@ -344,6 +345,7 @@ nano::error nano::node_config::deserialize_toml (nano::tomlconfig & toml)
 		toml.get<bool> ("use_memory_pools", use_memory_pools);
 		toml.get<std::size_t> ("confirmation_history_size", confirmation_history_size);
 		toml.get<std::size_t> ("active_elections_size", active_elections_size);
+		toml.get<std::size_t> ("active_elections_hinted_limit", active_elections_hinted_limit);
 		toml.get<std::size_t> ("bandwidth_limit", bandwidth_limit);
 		toml.get<double> ("bandwidth_limit_burst_ratio", bandwidth_limit_burst_ratio);
 		toml.get<bool> ("backup_before_upgrade", backup_before_upgrade);
@@ -406,6 +408,10 @@ nano::error nano::node_config::deserialize_toml (nano::tomlconfig & toml)
 		{
 			toml.get_error ().set ("active_elections_size must be greater than 250");
 		}
+		if (active_elections_hinted_limit > active_elections_size)
+		{
+			toml.get_error ().set ("active_elections_hinted_limit cannot be greater than active_elections_size");
+		}
 		if (bandwidth_limit > std::numeric_limits<std::size_t>::max ())
 		{
 			toml.get_error ().set ("bandwidth_limit unbounded = 0, default = 10485760, max = 18446744073709551615");
@@ -514,6 +520,7 @@ nano::error nano::node_config::serialize_json (nano::jsonconfig & json) const
 	json.put_child ("diagnostics", diagnostics_l);
 	json.put ("confirmation_history_size", confirmation_history_size);
 	json.put ("active_elections_size", active_elections_size);
+	json.put ("active_elections_hinted_limit", active_elections_hinted_limit);
 	json.put ("bandwidth_limit", bandwidth_limit);
 	json.put ("backup_before_upgrade", backup_before_upgrade);
 	json.put ("work_watcher_period", 5);