From 37d9720136d9ed888b9decd62d9cc3e39da9052c Mon Sep 17 00:00:00 2001
From: Sergey Kroshnin <sergiysw@gmail.com>
Date: Tue, 5 Feb 2019 20:32:06 +0300
Subject: [PATCH] Request confirmation faster for new blocks (#1518)

* Broadcast new blocks & request confirmation faster

* Limit max broadcast_confirm_req

* Minimum broadcast of 2 * sqrt or 100 peers

* Disable fast broadcast with large broadcast queue

* Use std:chrono for confirmation_request_delay

* Formatting

* Formatting

* Braced initialization test

* Clang formatting

* Move fast broadcast to block_processor::process_receive_one

* Remove extra checks

* static_cast<size_t>

* Fix

* FIx merge

* Add missing declaration

* Check if votes were already requested
---
 nano/node/blockprocessor.cpp | 24 ++++++++++++++++++++++++
 nano/node/blockprocessor.hpp |  2 ++
 nano/node/node.cpp           |  4 ++--
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/nano/node/blockprocessor.cpp b/nano/node/blockprocessor.cpp
index 4bd5379f7..d93ade8dc 100644
--- a/nano/node/blockprocessor.cpp
+++ b/nano/node/blockprocessor.cpp
@@ -4,6 +4,8 @@
 #include <nano/node/node.hpp>
 #include <nano/secure/blockstore.hpp>
 
+std::chrono::milliseconds constexpr nano::block_processor::confirmation_request_delay;
+
 nano::block_processor::block_processor (nano::node & node_a) :
 generator (node_a, nano::is_test_network ? std::chrono::milliseconds (10) : std::chrono::milliseconds (500)),
 stopped (false),
@@ -349,6 +351,28 @@ void nano::block_processor::process_live (nano::block_hash const & hash_a, std::
 		// Announce our weighted vote to the network
 		generator.add (hash_a);
 	}
+	// Request confirmation for new block with delay
+	std::weak_ptr<nano::node> node_w (node.shared ());
+	node.alarm.add (std::chrono::steady_clock::now () + confirmation_request_delay, [node_w, block_a]() {
+		if (auto node_l = node_w.lock ())
+		{
+			// Check if votes were already requested
+			bool send_request (false);
+			{
+				std::lock_guard<std::mutex> lock (node_l->active.mutex);
+				auto existing (node_l->active.blocks.find (block_a->hash ()));
+				if (existing != node_l->active.blocks.end () && !existing->second->confirmed && !existing->second->stopped && existing->second->announcements == 0)
+				{
+					send_request = true;
+				}
+			}
+			// Request votes
+			if (send_request)
+			{
+				node_l->network.broadcast_confirm_req (block_a);
+			}
+		}
+	});
 }
 
 nano::process_return nano::block_processor::process_one (nano::transaction const & transaction_a, nano::unchecked_info info_a)
diff --git a/nano/node/blockprocessor.hpp b/nano/node/blockprocessor.hpp
index c498b8452..8b8221483 100644
--- a/nano/node/blockprocessor.hpp
+++ b/nano/node/blockprocessor.hpp
@@ -44,6 +44,8 @@ public:
 	nano::process_return process_one (nano::transaction const &, nano::unchecked_info);
 	nano::process_return process_one (nano::transaction const &, std::shared_ptr<nano::block>);
 	nano::vote_generator generator;
+	// Delay required for average network propagartion before requesting confirmation
+	static std::chrono::milliseconds constexpr confirmation_request_delay{ 1500 };
 
 private:
 	void queue_unchecked (nano::transaction const &, nano::block_hash const &);
diff --git a/nano/node/node.cpp b/nano/node/node.cpp
index 445ca813f..7fbc36fee 100644
--- a/nano/node/node.cpp
+++ b/nano/node/node.cpp
@@ -422,8 +422,8 @@ void nano::network::broadcast_confirm_req (std::shared_ptr<nano::block> block_a)
 	auto list (std::make_shared<std::vector<nano::peer_information>> (node.peers.representatives (std::numeric_limits<size_t>::max ())));
 	if (list->empty () || node.peers.total_weight () < node.config.online_weight_minimum.number ())
 	{
-		// broadcast request to all peers
-		list = std::make_shared<std::vector<nano::peer_information>> (node.peers.list_vector (100));
+		// broadcast request to all peers (with max limit 2 * sqrt (peers count))
+		list = std::make_shared<std::vector<nano::peer_information>> (node.peers.list_vector (std::min (static_cast<size_t> (100), 2 * node.peers.size_sqrt ())));
 	}
 
 	/*