Split election drop stats to be either overflow or expired (#3297)

At the moment it's not clear if elections are simply expiring after 5 minutes or being dropped due to the container overflowing. This should give us a better insight and allow us to monitor the situation.

Author: MajorChump

nano/core_test/active_transactions.cpp

@@ -613,7 +613,7 @@ TEST (active_transactions, dropped_cleanup)
 	ASSERT_FALSE (node.network.publish_filter.apply (block_bytes.data (), block_bytes.size ()));
 
 	// An election was recently dropped
-	ASSERT_EQ (1, node.stats.count (nano::stat::type::election, nano::stat::detail::election_drop));
+	ASSERT_EQ (1, node.stats.count (nano::stat::type::election, nano::stat::detail::election_drop_all));
 
 	// Block cleared from active
 	ASSERT_EQ (0, node.active.blocks.count (block->hash ()));
@@ -632,7 +632,7 @@ TEST (active_transactions, dropped_cleanup)
 	ASSERT_TRUE (node.network.publish_filter.apply (block_bytes.data (), block_bytes.size ()));
 
 	// Not dropped
-	ASSERT_EQ (1, node.stats.count (nano::stat::type::election, nano::stat::detail::election_drop));
+	ASSERT_EQ (1, node.stats.count (nano::stat::type::election, nano::stat::detail::election_drop_all));
 
 	// Block cleared from active
 	ASSERT_EQ (0, node.active.blocks.count (block->hash ()));
@@ -1525,6 +1525,8 @@ TEST (active_transactions, fifo)
 	ASSERT_TIMELY (1s, node.active.election (receive1->qualified_root ()) != nullptr);
 	// Ensure excess transactions get trimmed
 	ASSERT_TIMELY (1s, node.active.size () == 1);
+	// Ensure overflow stats have been incremented
+	ASSERT_EQ (1, node.stats.count (nano::stat::type::election, nano::stat::detail::election_drop_overflow));
 	// Ensure the surviving transaction is the least recently inserted
 	ASSERT_TIMELY (1s, node.active.election (receive1->qualified_root ()) != nullptr);
 }

nano/lib/stats.cpp

@@ -739,8 +739,14 @@ std::string nano::stat::detail_to_string (uint32_t key)
 		case nano::stat::detail::election_difficulty_update:
 			res = "election_difficulty_update";
 			break;
-		case nano::stat::detail::election_drop:
-			res = "election_drop";
+		case nano::stat::detail::election_drop_expired:
+			res = "election_drop_expired";
+			break;
+		case nano::stat::detail::election_drop_overflow:
+			res = "election_drop_overflow";
+			break;
+		case nano::stat::detail::election_drop_all:
+			res = "election_drop_all";
 			break;
 		case nano::stat::detail::election_restart:
 			res = "election_restart";

nano/lib/stats.hpp

@@ -318,7 +318,9 @@ class stat final
 		election_start,
 		election_block_conflict,
 		election_difficulty_update,
-		election_drop,
+		election_drop_expired,
+		election_drop_overflow,
+		election_drop_all,
 		election_restart,
 
 		// udp

nano/node/active_transactions.cpp

@@ -316,6 +316,7 @@ void nano::active_transactions::request_confirm (nano::unique_lock<nano::mutex>
 	for (auto const & election_l : elections_l)
 	{
 		bool const confirmed_l (election_l->confirmed ());
+		unconfirmed_count_l += !confirmed_l;
 
 		if (election_l->transition_time (solicitor))
 		{
@@ -330,6 +331,10 @@ void nano::active_transactions::request_confirm (nano::unique_lock<nano::mutex>
 			}
 
 			// Locks active mutex, cleans up the election and erases it from the main container
+			if (!confirmed_l)
+			{
+				node.stats.inc (nano::stat::type::election, nano::stat::detail::election_drop_expired);
+			}
 			erase (election_l->qualified_root);
 		}
 	}
@@ -349,7 +354,7 @@ void nano::active_transactions::cleanup_election (nano::unique_lock<nano::mutex>
 {
 	if (!election.confirmed ())
 	{
-		node.stats.inc (nano::stat::type::election, nano::stat::detail::election_drop);
+		node.stats.inc (nano::stat::type::election, nano::stat::detail::election_drop_all);
 	}
 
 	auto blocks_l = election.blocks ();
@@ -1049,6 +1054,7 @@ void nano::active_transactions::erase_oldest ()
 	nano::unique_lock<nano::mutex> lock (mutex);
 	if (!roots.empty ())
 	{
+		node.stats.inc (nano::stat::type::election, nano::stat::detail::election_drop_overflow);
 		auto item = roots.get<tag_random_access> ().front ();
 		cleanup_election (lock, *item.election);
 	}