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Storing blocks according to tally in elections with forks (#3026)
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* Storing blocks according to tally in elections with forks

Additionally store tally in inactive votes cache

* Fix build error

* Update test

* Fix build

* Apply Wesley review

* Apply Wesley review

* Replace assert with if condition (Colin review)

* Remove hash from active container

* Drop removed blocks from inactive votes ilter

* Improve election::remove_block ()

* Replace assert with if condition (Guilherme & Colin review)

* Unlock before sorting (Guilherme review)
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@SergiySW
SergiySW authored Jan 5, 2021
1 parent 38cbfa4 commit 1c5b940
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Showing 5 changed files with 246 additions and 3 deletions.
144 changes: 144 additions & 0 deletions nano/core_test/active_transactions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -850,6 +850,150 @@ TEST (active_transactions, fork_filter_cleanup)
ASSERT_EQ (10, election->blocks ().size ());
}

TEST (active_transactions, fork_replacement_tally)
{
nano::system system;
nano::node_config node_config (nano::get_available_port (), system.logging);
node_config.frontiers_confirmation = nano::frontiers_confirmation_mode::disabled;
auto & node1 (*system.add_node (node_config));

nano::genesis genesis;
size_t reps_count = 20;
size_t const max_blocks = 10;
std::vector<nano::keypair> keys (reps_count);
auto latest (genesis.hash ());
auto balance (nano::genesis_amount);
auto amount (node1.minimum_principal_weight ());
nano::state_block_builder builder;

// Create 20 representatives & confirm blocks
for (auto i (0); i < reps_count; i++)
{
balance -= amount + i;
auto send = builder.make_block ()
.account (nano::dev_genesis_key.pub)
.previous (latest)
.representative (nano::dev_genesis_key.pub)
.balance (balance)
.link (keys[i].pub)
.sign (nano::dev_genesis_key.prv, nano::dev_genesis_key.pub)
.work (*system.work.generate (latest))
.build_shared ();
node1.process_active (send);
latest = send->hash ();
auto open = builder.make_block ()
.account (keys[i].pub)
.previous (0)
.representative (keys[i].pub)
.balance (amount + i)
.link (send->hash ())
.sign (keys[i].prv, keys[i].pub)
.work (*system.work.generate (keys[i].pub))
.build_shared ();
node1.process_active (open);
// Confirmation
auto vote (std::make_shared<nano::vote> (nano::dev_genesis_key.pub, nano::dev_genesis_key.prv, 0, std::vector<nano::block_hash>{ send->hash (), open->hash () }));
node1.vote_processor.vote (vote, std::make_shared<nano::transport::channel_loopback> (node1));
}
node1.block_processor.flush ();
ASSERT_TIMELY (5s, node1.ledger.cache.cemented_count == 1 + 2 * reps_count);

nano::keypair key;
auto send_last = builder.make_block ()
.account (nano::dev_genesis_key.pub)
.previous (latest)
.representative (nano::dev_genesis_key.pub)
.balance (balance - 2 * nano::Gxrb_ratio)
.link (key.pub)
.sign (nano::dev_genesis_key.prv, nano::dev_genesis_key.pub)
.work (*system.work.generate (latest))
.build_shared ();

// Forks without votes
for (auto i (0); i < reps_count; i++)
{
auto fork = builder.make_block ()
.account (nano::dev_genesis_key.pub)
.previous (latest)
.representative (nano::dev_genesis_key.pub)
.balance (balance - nano::Gxrb_ratio - i)
.link (key.pub)
.sign (nano::dev_genesis_key.prv, nano::dev_genesis_key.pub)
.work (*system.work.generate (latest))
.build_shared ();
node1.process_active (fork);
}
node1.block_processor.flush ();
ASSERT_TIMELY (3s, !node1.active.empty ());
// Check overflow of blocks
auto election (node1.active.election (send_last->qualified_root ()));
ASSERT_NE (nullptr, election);
ASSERT_EQ (max_blocks, election->blocks ().size ());

// Generate forks with votes to prevent new block insertion to election
for (auto i (0); i < reps_count; i++)
{
auto fork = builder.make_block ()
.account (nano::dev_genesis_key.pub)
.previous (latest)
.representative (nano::dev_genesis_key.pub)
.balance (balance - 1 - i)
.link (key.pub)
.sign (nano::dev_genesis_key.prv, nano::dev_genesis_key.pub)
.work (*system.work.generate (latest))
.build_shared ();
auto vote (std::make_shared<nano::vote> (keys[i].pub, keys[i].prv, 0, std::vector<nano::block_hash>{ fork->hash () }));
node1.vote_processor.vote (vote, std::make_shared<nano::transport::channel_loopback> (node1));
node1.vote_processor.flush ();
node1.process_active (fork);
}
node1.block_processor.flush ();
// Check overflow of blocks
ASSERT_EQ (max_blocks, election->blocks ().size ());
// Check that only max weight blocks remains (and start winner)
auto votes1 (election->votes ());
ASSERT_EQ (max_blocks, votes1.size ());
for (auto i (max_blocks + 1); i < reps_count; i++)
{
ASSERT_TRUE (votes1.find (keys[i].pub) != votes1.end ());
}

// Process correct block
node_config.peering_port = nano::get_available_port ();
auto & node2 (*system.add_node (node_config));
node2.network.flood_block (send_last);
ASSERT_TIMELY (3s, node1.stats.count (nano::stat::type::message, nano::stat::detail::publish, nano::stat::dir::in) > 0);
node1.block_processor.flush ();
std::this_thread::sleep_for (50ms);

// Correct block without votes is ignored
auto blocks1 (election->blocks ());
ASSERT_EQ (max_blocks, blocks1.size ());
ASSERT_FALSE (blocks1.find (send_last->hash ()) != blocks1.end ());

// Process vote for correct block & replace existing lowest tally block
auto vote (std::make_shared<nano::vote> (nano::dev_genesis_key.pub, nano::dev_genesis_key.prv, 0, std::vector<nano::block_hash>{ send_last->hash () }));
node1.vote_processor.vote (vote, std::make_shared<nano::transport::channel_loopback> (node1));
node1.vote_processor.flush ();
node2.network.flood_block (send_last);
ASSERT_TIMELY (3s, node1.stats.count (nano::stat::type::message, nano::stat::detail::publish, nano::stat::dir::in) > 1);
node1.block_processor.flush ();
std::this_thread::sleep_for (50ms);

auto blocks2 (election->blocks ());
ASSERT_EQ (max_blocks, blocks2.size ());
ASSERT_TRUE (blocks2.find (send_last->hash ()) != blocks2.end ());
auto votes2 (election->votes ());
ASSERT_EQ (max_blocks, votes2.size ());
for (auto i (max_blocks + 2); i < reps_count; i++)
{
ASSERT_TRUE (votes2.find (keys[i].pub) != votes2.end ());
}
ASSERT_FALSE (votes2.find (keys[max_blocks].pub) != votes2.end ());
ASSERT_FALSE (votes2.find (keys[max_blocks + 1].pub) != votes2.end ());
ASSERT_TRUE (votes2.find (nano::dev_genesis_key.pub) != votes2.end ());
}

namespace nano
{
// Blocks that won an election must always be seen as confirming or cemented
Expand Down
8 changes: 8 additions & 0 deletions nano/node/active_transactions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1239,6 +1239,13 @@ void nano::active_transactions::erase (nano::qualified_root const & root_a)
}
}

void nano::active_transactions::erase_hash (nano::block_hash const & hash_a)
{
nano::unique_lock<std::mutex> lock (mutex);
[[maybe_unused]] auto erased (blocks.erase (hash_a));
debug_assert (erased == 1);
}

bool nano::active_transactions::empty ()
{
nano::lock_guard<std::mutex> lock (mutex);
Expand Down Expand Up @@ -1460,6 +1467,7 @@ nano::inactive_cache_status nano::active_transactions::inactive_votes_bootstrap_
{
tally += node.ledger.weight (voter);
}
status.tally = tally;

if (!previously_a.confirmed && tally >= node.online_reps.delta ())
{
Expand Down
4 changes: 3 additions & 1 deletion nano/node/active_transactions.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -55,10 +55,11 @@ class inactive_cache_status final
bool bootstrap_started{ false };
bool election_started{ false }; // Did item reach config threshold to start an impromptu election?
bool confirmed{ false }; // Did item reach votes quorum? (minimum config value)
nano::uint128_t tally{ 0 }; // Last votes tally for block

bool operator!= (inactive_cache_status const other) const
{
return bootstrap_started != other.bootstrap_started || election_started != other.election_started || confirmed != other.confirmed;
return bootstrap_started != other.bootstrap_started || election_started != other.election_started || confirmed != other.confirmed || tally != other.tally;
}
};

Expand Down Expand Up @@ -198,6 +199,7 @@ class active_transactions final
uint64_t limited_active_difficulty (nano::work_version const, uint64_t const);
double active_multiplier ();
void erase (nano::block const &);
void erase_hash (nano::block_hash const &);
bool empty ();
size_t size ();
void stop ();
Expand Down
90 changes: 88 additions & 2 deletions nano/node/election.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -390,13 +390,14 @@ bool nano::election::publish (std::shared_ptr<nano::block> const & block_a)

// Do not insert new blocks if already confirmed
auto result (confirmed ());
if (!result && last_blocks.size () >= 10)
if (!result && last_blocks.size () >= max_blocks && last_blocks.find (block_a->hash ()) == last_blocks.end ())
{
if (last_tally[block_a->hash ()] < node.online_reps.trended () / 10)
if (!replace_by_weight (lock, block_a->hash ()))
{
result = true;
node.network.publish_filter.clear (block_a);
}
debug_assert (lock.owns_lock ());
}
if (!result)
{
Expand All @@ -415,6 +416,12 @@ bool nano::election::publish (std::shared_ptr<nano::block> const & block_a)
}
}
}
/*
Result is true if:
1) election is confirmed or expired
2) given election contains 10 blocks & new block didn't receive enough votes to replace existing blocks
3) given block in already in election & election contains less than 10 blocks (replacing block content with new)
*/
return result;
}

Expand Down Expand Up @@ -524,6 +531,85 @@ void nano::election::remove_votes (nano::block_hash const & hash_a)
}
}

void nano::election::remove_block (nano::block_hash const & hash_a)
{
debug_assert (!mutex.try_lock ());
if (status.winner->hash () != hash_a)
{
if (auto existing = last_blocks.find (hash_a); existing != last_blocks.end ())
{
for (auto i (last_votes.begin ()); i != last_votes.end ();)
{
if (i->second.hash == hash_a)
{
i = last_votes.erase (i);
}
else
{
++i;
}
}
node.network.publish_filter.clear (existing->second);
last_blocks.erase (hash_a);
}
}
}

bool nano::election::replace_by_weight (nano::unique_lock<std::mutex> & lock_a, nano::block_hash const & hash_a)
{
debug_assert (lock_a.owns_lock ());
nano::block_hash replaced_block (0);
auto winner_hash (status.winner->hash ());
// Sort existing blocks tally
std::vector<std::pair<nano::block_hash, nano::uint128_t>> sorted;
sorted.reserve (last_tally.size ());
std::copy (last_tally.begin (), last_tally.end (), std::back_inserter (sorted));
lock_a.unlock ();
// Sort in ascending order
std::sort (sorted.begin (), sorted.end (), [](auto const & left, auto const & right) { return left.second < right.second; });
// Replace if lowest tally is below inactive cache new block weight
auto inactive_existing (node.active.find_inactive_votes_cache (hash_a));
auto inactive_tally (inactive_existing.status.tally);
if (inactive_tally > 0 && sorted.size () < max_blocks)
{
// If count of tally items is less than 10, remove any block without tally
for (auto const & [hash, block] : blocks ())
{
if (std::find_if (sorted.begin (), sorted.end (), [& hash = hash](auto const & item_a) { return item_a.first == hash; }) == sorted.end () && hash != winner_hash)
{
replaced_block = hash;
break;
}
}
}
else if (inactive_tally > 0 && inactive_tally > sorted.front ().second)
{
if (sorted.front ().first != winner_hash)
{
replaced_block = sorted.front ().first;
}
else if (inactive_tally > sorted[1].second)
{
// Avoid removing winner
replaced_block = sorted[1].first;
}
}

bool replaced (false);
if (!replaced_block.is_zero ())
{
node.active.erase_hash (replaced_block);
lock_a.lock ();
remove_block (replaced_block);
replaced = true;
}
else
{
lock_a.lock ();
}
return replaced;
}

void nano::election::force_confirm (nano::election_status_type type_a)
{
release_assert (node.network_params.network.is_dev_network ());
Expand Down
3 changes: 3 additions & 0 deletions nano/node/election.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -126,6 +126,8 @@ class election final : public std::enable_shared_from_this<nano::election>
// Calculate votes for local representatives
void generate_votes () const;
void remove_votes (nano::block_hash const &);
void remove_block (nano::block_hash const &);
bool replace_by_weight (nano::unique_lock<std::mutex> & lock_a, nano::block_hash const &);
nano::election_cleanup_info cleanup_info_impl () const;

private:
Expand All @@ -140,6 +142,7 @@ class election final : public std::enable_shared_from_this<nano::election>
mutable std::mutex mutex;

static std::chrono::seconds constexpr late_blocks_delay{ 5 };
static size_t constexpr max_blocks{ 10 };

friend class active_transactions;
friend class confirmation_solicitor;
Expand Down

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