From 5245414dee52924b5624d7a5df9bf77a98e6f40b Mon Sep 17 00:00:00 2001
From: Sergey Kroshnin <sergiysw@gmail.com>
Date: Mon, 14 Jan 2019 16:06:05 +0300
Subject: [PATCH] List of rolled back blocks in block_processor (#1581)

* List of rolled back blocks in block_processor

With limit 1024

* Update node.cpp

* Make rolled_back_max static const
---
 nano/node/node.cpp | 19 +++++++++++++++++--
 nano/node/node.hpp | 13 +++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/nano/node/node.cpp b/nano/node/node.cpp
index 96a28535..dccac56f 100644
--- a/nano/node/node.cpp
+++ b/nano/node/node.cpp
@@ -1232,8 +1232,9 @@ void nano::block_processor::add (std::shared_ptr<nano::block> block_a, std::chro
 	if (!nano::work_validate (block_a->root (), block_a->block_work ()))
 	{
 		{
+			auto hash (block_a->hash ());
 			std::lock_guard<std::mutex> lock (mutex);
-			if (blocks_hashes.find (block_a->hash ()) == blocks_hashes.end ())
+			if (blocks_hashes.find (hash) == blocks_hashes.end () && rolled_back.get<1> ().find (hash) == rolled_back.get<1> ().end ())
 			{
 				if (block_a->type () == nano::block_type::state && !node.ledger.is_epoch_link (block_a->link ()))
 				{
@@ -1243,7 +1244,7 @@ void nano::block_processor::add (std::shared_ptr<nano::block> block_a, std::chro
 				{
 					blocks.push_back (std::make_pair (block_a, origination));
 				}
-				blocks_hashes.insert (block_a->hash ());
+				blocks_hashes.insert (hash);
 			}
 			condition.notify_all ();
 		}
@@ -1431,6 +1432,20 @@ void nano::block_processor::process_batch (std::unique_lock<std::mutex> & lock_a
 				// Replace our block with the winner and roll back any dependent blocks
 				BOOST_LOG (node.log) << boost::str (boost::format ("Rolling back %1% and replacing with %2%") % successor->hash ().to_string () % hash.to_string ());
 				node.ledger.rollback (transaction, successor->hash ());
+				lock_a.lock ();
+				// Prevent rolled back blocks second insertion
+				auto inserted (rolled_back.insert (nano::rolled_hash{ std::chrono::steady_clock::now (), successor->hash () }));
+				if (inserted.second)
+				{
+					// Possible election winner change
+					rolled_back.get<1> ().erase (hash);
+					// Prevent overflow
+					if (rolled_back.size () > rolled_back_max)
+					{
+						rolled_back.erase (rolled_back.begin ());
+					}
+				}
+				lock_a.unlock ();
 			}
 		}
 		/* Forced state blocks are not validated in verify_state_blocks () function
diff --git a/nano/node/node.hpp b/nano/node/node.hpp
index 2a161a7b..ca99d68d 100644
--- a/nano/node/node.hpp
+++ b/nano/node/node.hpp
@@ -410,6 +410,12 @@ private:
 	std::condition_variable condition;
 	std::thread thread;
 };
+class rolled_hash
+{
+public:
+	std::chrono::steady_clock::time_point time;
+	nano::block_hash hash;
+};
 // Processing blocks is a potentially long IO operation
 // This class isolates block insertion from other operations like servicing network operations
 class block_processor
@@ -438,6 +444,13 @@ private:
 	std::deque<std::pair<std::shared_ptr<nano::block>, std::chrono::steady_clock::time_point>> blocks;
 	std::unordered_set<nano::block_hash> blocks_hashes;
 	std::deque<std::shared_ptr<nano::block>> forced;
+	boost::multi_index_container<
+	nano::rolled_hash,
+	boost::multi_index::indexed_by<
+	boost::multi_index::ordered_non_unique<boost::multi_index::member<nano::rolled_hash, std::chrono::steady_clock::time_point, &nano::rolled_hash::time>>,
+	boost::multi_index::hashed_unique<boost::multi_index::member<nano::rolled_hash, nano::block_hash, &nano::rolled_hash::hash>>>>
+	rolled_back;
+	static size_t const rolled_back_max = 1024;
 	std::condition_variable condition;
 	nano::node & node;
 	nano::vote_generator generator;