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litecoin/src/txrequest.cpp

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// Copyright (c) 2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <txrequest.h>
#include <crypto/siphash.h>
#include <net.h>
#include <primitives/transaction.h>
#include <random.h>
#include <uint256.h>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <chrono>
#include <unordered_map>
#include <utility>
#include <assert.h>
namespace {
/** The various states a (txhash,peer) pair can be in.
*
* Note that CANDIDATE is split up into 3 substates (DELAYED, BEST, READY), allowing more efficient implementation.
* Also note that the sorting order of ByTxHashView relies on the specific order of values in this enum.
*
* Expected behaviour is:
* - When first announced by a peer, the state is CANDIDATE_DELAYED until reqtime is reached.
* - Announcements that have reached their reqtime but not been requested will be either CANDIDATE_READY or
* CANDIDATE_BEST. Neither of those has an expiration time; they remain in that state until they're requested or
* no longer needed. CANDIDATE_READY announcements are promoted to CANDIDATE_BEST when they're the best one left.
* - When requested, an announcement will be in state REQUESTED until expiry is reached.
* - If expiry is reached, or the peer replies to the request (either with NOTFOUND or the tx), the state becomes
* COMPLETED.
*/
enum class State : uint8_t {
/** A CANDIDATE announcement whose reqtime is in the future. */
CANDIDATE_DELAYED,
/** A CANDIDATE announcement that's not CANDIDATE_DELAYED or CANDIDATE_BEST. */
CANDIDATE_READY,
/** The best CANDIDATE for a given txhash; only if there is no REQUESTED announcement already for that txhash.
* The CANDIDATE_BEST is the highest-priority announcement among all CANDIDATE_READY (and _BEST) ones for that
* txhash. */
CANDIDATE_BEST,
/** A REQUESTED announcement. */
REQUESTED,
/** A COMPLETED announcement. */
COMPLETED,
};
//! Type alias for sequence numbers.
using SequenceNumber = uint64_t;
/** An announcement. This is the data we track for each txid or wtxid that is announced to us by each peer. */
struct Announcement {
/** Txid or wtxid that was announced. */
const uint256 m_txhash;
/** For CANDIDATE_{DELAYED,BEST,READY} the reqtime; for REQUESTED the expiry. */
std::chrono::microseconds m_time;
/** What peer the request was from. */
const NodeId m_peer;
/** What sequence number this announcement has. */
const SequenceNumber m_sequence : 59;
/** Whether the request is preferred. */
const bool m_preferred : 1;
/** Whether this is a wtxid request. */
const bool m_is_wtxid : 1;
/** What state this announcement is in.
* This is a uint8_t instead of a State to silence a GCC warning in versions prior to 8.4 and 9.3.
* See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414 */
uint8_t m_state : 3;
/** Convert m_state to a State enum. */
State GetState() const { return static_cast<State>(m_state); }
/** Convert a State enum to a uint8_t and store it in m_state. */
void SetState(State state) { m_state = static_cast<uint8_t>(state); }
/** Whether this announcement is selected. There can be at most 1 selected peer per txhash. */
bool IsSelected() const
{
return GetState() == State::CANDIDATE_BEST || GetState() == State::REQUESTED;
}
/** Whether this announcement is waiting for a certain time to pass. */
bool IsWaiting() const
{
return GetState() == State::REQUESTED || GetState() == State::CANDIDATE_DELAYED;
}
/** Whether this announcement can feasibly be selected if the current IsSelected() one disappears. */
bool IsSelectable() const
{
return GetState() == State::CANDIDATE_READY || GetState() == State::CANDIDATE_BEST;
}
/** Construct a new announcement from scratch, initially in CANDIDATE_DELAYED state. */
Announcement(const GenTxid& gtxid, NodeId peer, bool preferred, std::chrono::microseconds reqtime,
SequenceNumber sequence) :
m_txhash(gtxid.GetHash()), m_time(reqtime), m_peer(peer), m_sequence(sequence), m_preferred(preferred),
m_is_wtxid(gtxid.IsWtxid()), m_state(static_cast<uint8_t>(State::CANDIDATE_DELAYED)) {}
};
//! Type alias for priorities.
using Priority = uint64_t;
/** A functor with embedded salt that computes priority of an announcement.
*
* Higher priorities are selected first.
*/
class PriorityComputer {
const uint64_t m_k0, m_k1;
public:
explicit PriorityComputer(bool deterministic) :
m_k0{deterministic ? 0 : GetRand(0xFFFFFFFFFFFFFFFF)},
m_k1{deterministic ? 0 : GetRand(0xFFFFFFFFFFFFFFFF)} {}
Priority operator()(const uint256& txhash, NodeId peer, bool preferred) const
{
uint64_t low_bits = CSipHasher(m_k0, m_k1).Write(txhash.begin(), txhash.size()).Write(peer).Finalize() >> 1;
return low_bits | uint64_t{preferred} << 63;
}
Priority operator()(const Announcement& ann) const
{
return operator()(ann.m_txhash, ann.m_peer, ann.m_preferred);
}
};
// Definitions for the 3 indexes used in the main data structure.
//
// Each index has a By* type to identify it, a By*View data type to represent the view of announcement it is sorted
// by, and an By*ViewExtractor type to convert an announcement into the By*View type.
// See https://www.boost.org/doc/libs/1_58_0/libs/multi_index/doc/reference/key_extraction.html#key_extractors
// for more information about the key extraction concept.
// The ByPeer index is sorted by (peer, state == CANDIDATE_BEST, txhash)
//
// Uses:
// * Looking up existing announcements by peer/txhash, by checking both (peer, false, txhash) and
// (peer, true, txhash).
// * Finding all CANDIDATE_BEST announcements for a given peer in GetRequestable.
struct ByPeer {};
using ByPeerView = std::tuple<NodeId, bool, const uint256&>;
struct ByPeerViewExtractor
{
using result_type = ByPeerView;
result_type operator()(const Announcement& ann) const
{
return ByPeerView{ann.m_peer, ann.GetState() == State::CANDIDATE_BEST, ann.m_txhash};
}
};
// The ByTxHash index is sorted by (txhash, state, priority).
//
// Note: priority == 0 whenever state != CANDIDATE_READY.
//
// Uses:
// * Deleting all announcements with a given txhash in ForgetTxHash.
// * Finding the best CANDIDATE_READY to convert to CANDIDATE_BEST, when no other CANDIDATE_READY or REQUESTED
// announcement exists for that txhash.
// * Determining when no more non-COMPLETED announcements for a given txhash exist, so the COMPLETED ones can be
// deleted.
struct ByTxHash {};
using ByTxHashView = std::tuple<const uint256&, State, Priority>;
class ByTxHashViewExtractor {
const PriorityComputer& m_computer;
public:
explicit ByTxHashViewExtractor(const PriorityComputer& computer) : m_computer(computer) {}
using result_type = ByTxHashView;
result_type operator()(const Announcement& ann) const
{
const Priority prio = (ann.GetState() == State::CANDIDATE_READY) ? m_computer(ann) : 0;
return ByTxHashView{ann.m_txhash, ann.GetState(), prio};
}
};
enum class WaitState {
//! Used for announcements that need efficient testing of "is their timestamp in the future?".
FUTURE_EVENT,
//! Used for announcements whose timestamp is not relevant.
NO_EVENT,
//! Used for announcements that need efficient testing of "is their timestamp in the past?".
PAST_EVENT,
};
WaitState GetWaitState(const Announcement& ann)
{
if (ann.IsWaiting()) return WaitState::FUTURE_EVENT;
if (ann.IsSelectable()) return WaitState::PAST_EVENT;
return WaitState::NO_EVENT;
}
// The ByTime index is sorted by (wait_state, time).
//
// All announcements with a timestamp in the future can be found by iterating the index forward from the beginning.
// All announcements with a timestamp in the past can be found by iterating the index backwards from the end.
//
// Uses:
// * Finding CANDIDATE_DELAYED announcements whose reqtime has passed, and REQUESTED announcements whose expiry has
// passed.
// * Finding CANDIDATE_READY/BEST announcements whose reqtime is in the future (when the clock time went backwards).
struct ByTime {};
using ByTimeView = std::pair<WaitState, std::chrono::microseconds>;
struct ByTimeViewExtractor
{
using result_type = ByTimeView;
result_type operator()(const Announcement& ann) const
{
return ByTimeView{GetWaitState(ann), ann.m_time};
}
};
/** Data type for the main data structure (Announcement objects with ByPeer/ByTxHash/ByTime indexes). */
using Index = boost::multi_index_container<
Announcement,
boost::multi_index::indexed_by<
boost::multi_index::ordered_unique<boost::multi_index::tag<ByPeer>, ByPeerViewExtractor>,
boost::multi_index::ordered_non_unique<boost::multi_index::tag<ByTxHash>, ByTxHashViewExtractor>,
boost::multi_index::ordered_non_unique<boost::multi_index::tag<ByTime>, ByTimeViewExtractor>
>
>;
/** Helper type to simplify syntax of iterator types. */
template<typename Tag>
using Iter = typename Index::index<Tag>::type::iterator;
/** Per-peer statistics object. */
struct PeerInfo {
size_t m_total = 0; //!< Total number of announcements for this peer.
size_t m_completed = 0; //!< Number of COMPLETED announcements for this peer.
size_t m_requested = 0; //!< Number of REQUESTED announcements for this peer.
};
/** Per-txhash statistics object. Only used for sanity checking. */
struct TxHashInfo
{
//! Number of CANDIDATE_DELAYED announcements for this txhash.
size_t m_candidate_delayed = 0;
//! Number of CANDIDATE_READY announcements for this txhash.
size_t m_candidate_ready = 0;
//! Number of CANDIDATE_BEST announcements for this txhash (at most one).
size_t m_candidate_best = 0;
//! Number of REQUESTED announcements for this txhash (at most one; mutually exclusive with CANDIDATE_BEST).
size_t m_requested = 0;
//! The priority of the CANDIDATE_BEST announcement if one exists, or max() otherwise.
Priority m_priority_candidate_best = std::numeric_limits<Priority>::max();
//! The highest priority of all CANDIDATE_READY announcements (or min() if none exist).
Priority m_priority_best_candidate_ready = std::numeric_limits<Priority>::min();
//! All peers we have an announcement for this txhash for.
std::vector<NodeId> m_peers;
};
/** Compare two PeerInfo objects. Only used for sanity checking. */
bool operator==(const PeerInfo& a, const PeerInfo& b)
{
return std::tie(a.m_total, a.m_completed, a.m_requested) ==
std::tie(b.m_total, b.m_completed, b.m_requested);
};
/** (Re)compute the PeerInfo map from the index. Only used for sanity checking. */
std::unordered_map<NodeId, PeerInfo> RecomputePeerInfo(const Index& index)
{
std::unordered_map<NodeId, PeerInfo> ret;
for (const Announcement& ann : index) {
PeerInfo& info = ret[ann.m_peer];
++info.m_total;
info.m_requested += (ann.GetState() == State::REQUESTED);
info.m_completed += (ann.GetState() == State::COMPLETED);
}
return ret;
}
/** Compute the TxHashInfo map. Only used for sanity checking. */
std::map<uint256, TxHashInfo> ComputeTxHashInfo(const Index& index, const PriorityComputer& computer)
{
std::map<uint256, TxHashInfo> ret;
for (const Announcement& ann : index) {
TxHashInfo& info = ret[ann.m_txhash];
// Classify how many announcements of each state we have for this txhash.
info.m_candidate_delayed += (ann.GetState() == State::CANDIDATE_DELAYED);
info.m_candidate_ready += (ann.GetState() == State::CANDIDATE_READY);
info.m_candidate_best += (ann.GetState() == State::CANDIDATE_BEST);
info.m_requested += (ann.GetState() == State::REQUESTED);
// And track the priority of the best CANDIDATE_READY/CANDIDATE_BEST announcements.
if (ann.GetState() == State::CANDIDATE_BEST) {
info.m_priority_candidate_best = computer(ann);
}
if (ann.GetState() == State::CANDIDATE_READY) {
info.m_priority_best_candidate_ready = std::max(info.m_priority_best_candidate_ready, computer(ann));
}
// Also keep track of which peers this txhash has an announcement for (so we can detect duplicates).
info.m_peers.push_back(ann.m_peer);
}
return ret;
}
GenTxid ToGenTxid(const Announcement& ann)
{
return {ann.m_is_wtxid, ann.m_txhash};
}
} // namespace
/** Actual implementation for TxRequestTracker's data structure. */
class TxRequestTracker::Impl {
//! The current sequence number. Increases for every announcement. This is used to sort txhashes returned by
//! GetRequestable in announcement order.
SequenceNumber m_current_sequence{0};
//! This tracker's priority computer.
const PriorityComputer m_computer;
//! This tracker's main data structure. See SanityCheck() for the invariants that apply to it.
Index m_index;
//! Map with this tracker's per-peer statistics.
std::unordered_map<NodeId, PeerInfo> m_peerinfo;
public:
void SanityCheck() const
{
// Recompute m_peerdata from m_index. This verifies the data in it as it should just be caching statistics
// on m_index. It also verifies the invariant that no PeerInfo announcements with m_total==0 exist.
assert(m_peerinfo == RecomputePeerInfo(m_index));
// Calculate per-txhash statistics from m_index, and validate invariants.
for (auto& item : ComputeTxHashInfo(m_index, m_computer)) {
TxHashInfo& info = item.second;
// Cannot have only COMPLETED peer (txhash should have been forgotten already)
assert(info.m_candidate_delayed + info.m_candidate_ready + info.m_candidate_best + info.m_requested > 0);
// Can have at most 1 CANDIDATE_BEST/REQUESTED peer
assert(info.m_candidate_best + info.m_requested <= 1);
// If there are any CANDIDATE_READY announcements, there must be exactly one CANDIDATE_BEST or REQUESTED
// announcement.
if (info.m_candidate_ready > 0) {
assert(info.m_candidate_best + info.m_requested == 1);
}
// If there is both a CANDIDATE_READY and a CANDIDATE_BEST announcement, the CANDIDATE_BEST one must be
// at least as good (equal or higher priority) as the best CANDIDATE_READY.
if (info.m_candidate_ready && info.m_candidate_best) {
assert(info.m_priority_candidate_best >= info.m_priority_best_candidate_ready);
}
// No txhash can have been announced by the same peer twice.
std::sort(info.m_peers.begin(), info.m_peers.end());
assert(std::adjacent_find(info.m_peers.begin(), info.m_peers.end()) == info.m_peers.end());
}
}
void PostGetRequestableSanityCheck(std::chrono::microseconds now) const
{
for (const Announcement& ann : m_index) {
if (ann.IsWaiting()) {
// REQUESTED and CANDIDATE_DELAYED must have a time in the future (they should have been converted
// to COMPLETED/CANDIDATE_READY respectively).
assert(ann.m_time > now);
} else if (ann.IsSelectable()) {
// CANDIDATE_READY and CANDIDATE_BEST cannot have a time in the future (they should have remained
// CANDIDATE_DELAYED, or should have been converted back to it if time went backwards).
assert(ann.m_time <= now);
}
}
}
private:
//! Wrapper around Index::...::erase that keeps m_peerinfo up to date.
template<typename Tag>
Iter<Tag> Erase(Iter<Tag> it)
{
auto peerit = m_peerinfo.find(it->m_peer);
peerit->second.m_completed -= it->GetState() == State::COMPLETED;
peerit->second.m_requested -= it->GetState() == State::REQUESTED;
if (--peerit->second.m_total == 0) m_peerinfo.erase(peerit);
return m_index.get<Tag>().erase(it);
}
//! Wrapper around Index::...::modify that keeps m_peerinfo up to date.
template<typename Tag, typename Modifier>
void Modify(Iter<Tag> it, Modifier modifier)
{
auto peerit = m_peerinfo.find(it->m_peer);
peerit->second.m_completed -= it->GetState() == State::COMPLETED;
peerit->second.m_requested -= it->GetState() == State::REQUESTED;
m_index.get<Tag>().modify(it, std::move(modifier));
peerit->second.m_completed += it->GetState() == State::COMPLETED;
peerit->second.m_requested += it->GetState() == State::REQUESTED;
}
//! Convert a CANDIDATE_DELAYED announcement into a CANDIDATE_READY. If this makes it the new best
//! CANDIDATE_READY (and no REQUESTED exists) and better than the CANDIDATE_BEST (if any), it becomes the new
//! CANDIDATE_BEST.
void PromoteCandidateReady(Iter<ByTxHash> it)
{
assert(it != m_index.get<ByTxHash>().end());
assert(it->GetState() == State::CANDIDATE_DELAYED);
// Convert CANDIDATE_DELAYED to CANDIDATE_READY first.
Modify<ByTxHash>(it, [](Announcement& ann){ ann.SetState(State::CANDIDATE_READY); });
// The following code relies on the fact that the ByTxHash is sorted by txhash, and then by state (first
// _DELAYED, then _READY, then _BEST/REQUESTED). Within the _READY announcements, the best one (highest
// priority) comes last. Thus, if an existing _BEST exists for the same txhash that this announcement may
// be preferred over, it must immediately follow the newly created _READY.
auto it_next = std::next(it);
if (it_next == m_index.get<ByTxHash>().end() || it_next->m_txhash != it->m_txhash ||
it_next->GetState() == State::COMPLETED) {
// This is the new best CANDIDATE_READY, and there is no IsSelected() announcement for this txhash
// already.
Modify<ByTxHash>(it, [](Announcement& ann){ ann.SetState(State::CANDIDATE_BEST); });
} else if (it_next->GetState() == State::CANDIDATE_BEST) {
Priority priority_old = m_computer(*it_next);
Priority priority_new = m_computer(*it);
if (priority_new > priority_old) {
// There is a CANDIDATE_BEST announcement already, but this one is better.
Modify<ByTxHash>(it_next, [](Announcement& ann){ ann.SetState(State::CANDIDATE_READY); });
Modify<ByTxHash>(it, [](Announcement& ann){ ann.SetState(State::CANDIDATE_BEST); });
}
}
}
//! Change the state of an announcement to something non-IsSelected(). If it was IsSelected(), the next best
//! announcement will be marked CANDIDATE_BEST.
void ChangeAndReselect(Iter<ByTxHash> it, State new_state)
{
assert(new_state == State::COMPLETED || new_state == State::CANDIDATE_DELAYED);
assert(it != m_index.get<ByTxHash>().end());
if (it->IsSelected() && it != m_index.get<ByTxHash>().begin()) {
auto it_prev = std::prev(it);
// The next best CANDIDATE_READY, if any, immediately precedes the REQUESTED or CANDIDATE_BEST
// announcement in the ByTxHash index.
if (it_prev->m_txhash == it->m_txhash && it_prev->GetState() == State::CANDIDATE_READY) {
// If one such CANDIDATE_READY exists (for this txhash), convert it to CANDIDATE_BEST.
Modify<ByTxHash>(it_prev, [](Announcement& ann){ ann.SetState(State::CANDIDATE_BEST); });
}
}
Modify<ByTxHash>(it, [new_state](Announcement& ann){ ann.SetState(new_state); });
}
//! Check if 'it' is the only announcement for a given txhash that isn't COMPLETED.
bool IsOnlyNonCompleted(Iter<ByTxHash> it)
{
assert(it != m_index.get<ByTxHash>().end());
assert(it->GetState() != State::COMPLETED); // Not allowed to call this on COMPLETED announcements.
// This announcement has a predecessor that belongs to the same txhash. Due to ordering, and the
// fact that 'it' is not COMPLETED, its predecessor cannot be COMPLETED here.
if (it != m_index.get<ByTxHash>().begin() && std::prev(it)->m_txhash == it->m_txhash) return false;
// This announcement has a successor that belongs to the same txhash, and is not COMPLETED.
if (std::next(it) != m_index.get<ByTxHash>().end() && std::next(it)->m_txhash == it->m_txhash &&
std::next(it)->GetState() != State::COMPLETED) return false;
return true;
}
/** Convert any announcement to a COMPLETED one. If there are no non-COMPLETED announcements left for this
* txhash, they are deleted. If this was a REQUESTED announcement, and there are other CANDIDATEs left, the
* best one is made CANDIDATE_BEST. Returns whether the announcement still exists. */
bool MakeCompleted(Iter<ByTxHash> it)
{
assert(it != m_index.get<ByTxHash>().end());
// Nothing to be done if it's already COMPLETED.
if (it->GetState() == State::COMPLETED) return true;
if (IsOnlyNonCompleted(it)) {
// This is the last non-COMPLETED announcement for this txhash. Delete all.
uint256 txhash = it->m_txhash;
do {
it = Erase<ByTxHash>(it);
} while (it != m_index.get<ByTxHash>().end() && it->m_txhash == txhash);
return false;
}
// Mark the announcement COMPLETED, and select the next best announcement (the first CANDIDATE_READY) if
// needed.
ChangeAndReselect(it, State::COMPLETED);
return true;
}
//! Make the data structure consistent with a given point in time:
//! - REQUESTED annoucements with expiry <= now are turned into COMPLETED.
//! - CANDIDATE_DELAYED announcements with reqtime <= now are turned into CANDIDATE_{READY,BEST}.
//! - CANDIDATE_{READY,BEST} announcements with reqtime > now are turned into CANDIDATE_DELAYED.
void SetTimePoint(std::chrono::microseconds now, std::vector<std::pair<NodeId, GenTxid>>* expired)
{
if (expired) expired->clear();
// Iterate over all CANDIDATE_DELAYED and REQUESTED from old to new, as long as they're in the past,
// and convert them to CANDIDATE_READY and COMPLETED respectively.
while (!m_index.empty()) {
auto it = m_index.get<ByTime>().begin();
if (it->GetState() == State::CANDIDATE_DELAYED && it->m_time <= now) {
PromoteCandidateReady(m_index.project<ByTxHash>(it));
} else if (it->GetState() == State::REQUESTED && it->m_time <= now) {
if (expired) expired->emplace_back(it->m_peer, ToGenTxid(*it));
MakeCompleted(m_index.project<ByTxHash>(it));
} else {
break;
}
}
while (!m_index.empty()) {
// If time went backwards, we may need to demote CANDIDATE_BEST and CANDIDATE_READY announcements back
// to CANDIDATE_DELAYED. This is an unusual edge case, and unlikely to matter in production. However,
// it makes it much easier to specify and test TxRequestTracker::Impl's behaviour.
auto it = std::prev(m_index.get<ByTime>().end());
if (it->IsSelectable() && it->m_time > now) {
ChangeAndReselect(m_index.project<ByTxHash>(it), State::CANDIDATE_DELAYED);
} else {
break;
}
}
}
public:
explicit Impl(bool deterministic) :
m_computer(deterministic),
// Explicitly initialize m_index as we need to pass a reference to m_computer to ByTxHashViewExtractor.
m_index(boost::make_tuple(
boost::make_tuple(ByPeerViewExtractor(), std::less<ByPeerView>()),
boost::make_tuple(ByTxHashViewExtractor(m_computer), std::less<ByTxHashView>()),
boost::make_tuple(ByTimeViewExtractor(), std::less<ByTimeView>())
)) {}
// Disable copying and assigning (a default copy won't work due the stateful ByTxHashViewExtractor).
Impl(const Impl&) = delete;
Impl& operator=(const Impl&) = delete;
void DisconnectedPeer(NodeId peer)
{
auto& index = m_index.get<ByPeer>();
auto it = index.lower_bound(ByPeerView{peer, false, uint256::ZERO});
while (it != index.end() && it->m_peer == peer) {
// Check what to continue with after this iteration. 'it' will be deleted in what follows, so we need to
// decide what to continue with afterwards. There are a number of cases to consider:
// - std::next(it) is end() or belongs to a different peer. In that case, this is the last iteration
// of the loop (denote this by setting it_next to end()).
// - 'it' is not the only non-COMPLETED announcement for its txhash. This means it will be deleted, but
// no other Announcement objects will be modified. Continue with std::next(it) if it belongs to the
// same peer, but decide this ahead of time (as 'it' may change position in what follows).
// - 'it' is the only non-COMPLETED announcement for its txhash. This means it will be deleted along
// with all other announcements for the same txhash - which may include std::next(it). However, other
// than 'it', no announcements for the same peer can be affected (due to (peer, txhash) uniqueness).
// In other words, the situation where std::next(it) is deleted can only occur if std::next(it)
// belongs to a different peer but the same txhash as 'it'. This is covered by the first bulletpoint
// already, and we'll have set it_next to end().
auto it_next = (std::next(it) == index.end() || std::next(it)->m_peer != peer) ? index.end() :
std::next(it);
// If the announcement isn't already COMPLETED, first make it COMPLETED (which will mark other
// CANDIDATEs as CANDIDATE_BEST, or delete all of a txhash's announcements if no non-COMPLETED ones are
// left).
if (MakeCompleted(m_index.project<ByTxHash>(it))) {
// Then actually delete the announcement (unless it was already deleted by MakeCompleted).
Erase<ByPeer>(it);
}
it = it_next;
}
}
void ForgetTxHash(const uint256& txhash)
{
auto it = m_index.get<ByTxHash>().lower_bound(ByTxHashView{txhash, State::CANDIDATE_DELAYED, 0});
while (it != m_index.get<ByTxHash>().end() && it->m_txhash == txhash) {
it = Erase<ByTxHash>(it);
}
}
void ReceivedInv(NodeId peer, const GenTxid& gtxid, bool preferred,
std::chrono::microseconds reqtime)
{
// Bail out if we already have a CANDIDATE_BEST announcement for this (txhash, peer) combination. The case
// where there is a non-CANDIDATE_BEST announcement already will be caught by the uniqueness property of the
// ByPeer index when we try to emplace the new object below.
if (m_index.get<ByPeer>().count(ByPeerView{peer, true, gtxid.GetHash()})) return;
// Try creating the announcement with CANDIDATE_DELAYED state (which will fail due to the uniqueness
// of the ByPeer index if a non-CANDIDATE_BEST announcement already exists with the same txhash and peer).
// Bail out in that case.
auto ret = m_index.get<ByPeer>().emplace(gtxid, peer, preferred, reqtime, m_current_sequence);
if (!ret.second) return;
// Update accounting metadata.
++m_peerinfo[peer].m_total;
++m_current_sequence;
}
//! Find the GenTxids to request now from peer.
std::vector<GenTxid> GetRequestable(NodeId peer, std::chrono::microseconds now,
std::vector<std::pair<NodeId, GenTxid>>* expired)
{
// Move time.
SetTimePoint(now, expired);
// Find all CANDIDATE_BEST announcements for this peer.
std::vector<const Announcement*> selected;
auto it_peer = m_index.get<ByPeer>().lower_bound(ByPeerView{peer, true, uint256::ZERO});
while (it_peer != m_index.get<ByPeer>().end() && it_peer->m_peer == peer &&
it_peer->GetState() == State::CANDIDATE_BEST) {
selected.emplace_back(&*it_peer);
++it_peer;
}
// Sort by sequence number.
std::sort(selected.begin(), selected.end(), [](const Announcement* a, const Announcement* b) {
return a->m_sequence < b->m_sequence;
});
// Convert to GenTxid and return.
std::vector<GenTxid> ret;
ret.reserve(selected.size());
std::transform(selected.begin(), selected.end(), std::back_inserter(ret), [](const Announcement* ann) {
return ToGenTxid(*ann);
});
return ret;
}
void RequestedTx(NodeId peer, const uint256& txhash, std::chrono::microseconds expiry)
{
auto it = m_index.get<ByPeer>().find(ByPeerView{peer, true, txhash});
if (it == m_index.get<ByPeer>().end()) {
// There is no CANDIDATE_BEST announcement, look for a _READY or _DELAYED instead. If the caller only
// ever invokes RequestedTx with the values returned by GetRequestable, and no other non-const functions
// other than ForgetTxHash and GetRequestable in between, this branch will never execute (as txhashes
// returned by GetRequestable always correspond to CANDIDATE_BEST announcements).
it = m_index.get<ByPeer>().find(ByPeerView{peer, false, txhash});
if (it == m_index.get<ByPeer>().end() || (it->GetState() != State::CANDIDATE_DELAYED &&
it->GetState() != State::CANDIDATE_READY)) {
// There is no CANDIDATE announcement tracked for this peer, so we have nothing to do. Either this
// txhash wasn't tracked at all (and the caller should have called ReceivedInv), or it was already
// requested and/or completed for other reasons and this is just a superfluous RequestedTx call.
return;
}
// Look for an existing CANDIDATE_BEST or REQUESTED with the same txhash. We only need to do this if the
// found announcement had a different state than CANDIDATE_BEST. If it did, invariants guarantee that no
// other CANDIDATE_BEST or REQUESTED can exist.
auto it_old = m_index.get<ByTxHash>().lower_bound(ByTxHashView{txhash, State::CANDIDATE_BEST, 0});
if (it_old != m_index.get<ByTxHash>().end() && it_old->m_txhash == txhash) {
if (it_old->GetState() == State::CANDIDATE_BEST) {
// The data structure's invariants require that there can be at most one CANDIDATE_BEST or one
// REQUESTED announcement per txhash (but not both simultaneously), so we have to convert any
// existing CANDIDATE_BEST to another CANDIDATE_* when constructing another REQUESTED.
// It doesn't matter whether we pick CANDIDATE_READY or _DELAYED here, as SetTimePoint()
// will correct it at GetRequestable() time. If time only goes forward, it will always be
// _READY, so pick that to avoid extra work in SetTimePoint().
Modify<ByTxHash>(it_old, [](Announcement& ann) { ann.SetState(State::CANDIDATE_READY); });
} else if (it_old->GetState() == State::REQUESTED) {
// As we're no longer waiting for a response to the previous REQUESTED announcement, convert it
// to COMPLETED. This also helps guaranteeing progress.
Modify<ByTxHash>(it_old, [](Announcement& ann) { ann.SetState(State::COMPLETED); });
}
}
}
Modify<ByPeer>(it, [expiry](Announcement& ann) {
ann.SetState(State::REQUESTED);
ann.m_time = expiry;
});
}
void ReceivedResponse(NodeId peer, const uint256& txhash)
{
// We need to search the ByPeer index for both (peer, false, txhash) and (peer, true, txhash).
auto it = m_index.get<ByPeer>().find(ByPeerView{peer, false, txhash});
if (it == m_index.get<ByPeer>().end()) {
it = m_index.get<ByPeer>().find(ByPeerView{peer, true, txhash});
}
if (it != m_index.get<ByPeer>().end()) MakeCompleted(m_index.project<ByTxHash>(it));
}
size_t CountInFlight(NodeId peer) const
{
auto it = m_peerinfo.find(peer);
if (it != m_peerinfo.end()) return it->second.m_requested;
return 0;
}
size_t CountCandidates(NodeId peer) const
{
auto it = m_peerinfo.find(peer);
if (it != m_peerinfo.end()) return it->second.m_total - it->second.m_requested - it->second.m_completed;
return 0;
}
size_t Count(NodeId peer) const
{
auto it = m_peerinfo.find(peer);
if (it != m_peerinfo.end()) return it->second.m_total;
return 0;
}
//! Count how many announcements are being tracked in total across all peers and transactions.
size_t Size() const { return m_index.size(); }
uint64_t ComputePriority(const uint256& txhash, NodeId peer, bool preferred) const
{
// Return Priority as a uint64_t as Priority is internal.
return uint64_t{m_computer(txhash, peer, preferred)};
}
};
TxRequestTracker::TxRequestTracker(bool deterministic) :
m_impl{std::make_unique<TxRequestTracker::Impl>(deterministic)} {}
TxRequestTracker::~TxRequestTracker() = default;
void TxRequestTracker::ForgetTxHash(const uint256& txhash) { m_impl->ForgetTxHash(txhash); }
void TxRequestTracker::DisconnectedPeer(NodeId peer) { m_impl->DisconnectedPeer(peer); }
size_t TxRequestTracker::CountInFlight(NodeId peer) const { return m_impl->CountInFlight(peer); }
size_t TxRequestTracker::CountCandidates(NodeId peer) const { return m_impl->CountCandidates(peer); }
size_t TxRequestTracker::Count(NodeId peer) const { return m_impl->Count(peer); }
size_t TxRequestTracker::Size() const { return m_impl->Size(); }
void TxRequestTracker::SanityCheck() const { m_impl->SanityCheck(); }
void TxRequestTracker::PostGetRequestableSanityCheck(std::chrono::microseconds now) const
{
m_impl->PostGetRequestableSanityCheck(now);
}
void TxRequestTracker::ReceivedInv(NodeId peer, const GenTxid& gtxid, bool preferred,
std::chrono::microseconds reqtime)
{
m_impl->ReceivedInv(peer, gtxid, preferred, reqtime);
}
void TxRequestTracker::RequestedTx(NodeId peer, const uint256& txhash, std::chrono::microseconds expiry)
{
m_impl->RequestedTx(peer, txhash, expiry);
}
void TxRequestTracker::ReceivedResponse(NodeId peer, const uint256& txhash)
{
m_impl->ReceivedResponse(peer, txhash);
}
std::vector<GenTxid> TxRequestTracker::GetRequestable(NodeId peer, std::chrono::microseconds now,
std::vector<std::pair<NodeId, GenTxid>>* expired)
{
return m_impl->GetRequestable(peer, now, expired);
}
uint64_t TxRequestTracker::ComputePriority(const uint256& txhash, NodeId peer, bool preferred) const
{
return m_impl->ComputePriority(txhash, peer, preferred);
}
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