Integrate LruCache into transaction queue

Use LruCache to manage dropped transactions

Author: halfalicious

libethereum/TransactionQueue.cpp

@@ -11,13 +11,17 @@ using namespace std;
 using namespace dev;
 using namespace dev::eth;
 
+namespace
+{
 constexpr size_t c_maxVerificationQueueSize = 8192;
 constexpr size_t c_maxDroppedTransactionCount = 1024;
+}  // namespace
 
-TransactionQueue::TransactionQueue(unsigned _limit, unsigned _futureLimit):
-    m_current(PriorityCompare { *this }),
-    m_limit(_limit),
-    m_futureLimit(_futureLimit)
+TransactionQueue::TransactionQueue(unsigned _limit, unsigned _futureLimit)
+  : m_dropped{c_maxDroppedTransactionCount},
+    m_current{PriorityCompare{*this}},
+    m_limit{_limit},
+    m_futureLimit{_futureLimit}
 {
     unsigned verifierThreads = std::max(thread::hardware_concurrency(), 3U) - 2U;
     for (unsigned i = 0; i < verifierThreads; ++i)
@@ -54,7 +58,7 @@ ImportResult TransactionQueue::check_WITH_LOCK(h256 const& _h, IfDropped _ik)
     if (m_known.count(_h))
         return ImportResult::AlreadyKnown;
 
-    if (m_dropped.count(_h) && _ik == IfDropped::Ignore)
+    if (m_dropped.contains(_h) && _ik == IfDropped::Ignore)
         return ImportResult::AlreadyInChain;
 
     return ImportResult::Success;
@@ -312,15 +316,7 @@ void TransactionQueue::drop(h256 const& _txHash)
         return;
 
     UpgradeGuard ul(l);
-    if (m_dropped.size() == c_maxDroppedTransactionCount)
-    {
-        LOG(m_loggerDetail) << "Dropped transaction list is at capacity ("
-                            << c_maxDroppedTransactionCount
-                            << "), removing dropped transaction from list (txhash: "
-                            << *m_dropped.begin() << ")";
-        m_dropped.erase(m_dropped.begin());
-    }
-    m_dropped.insert(_txHash);
+    m_dropped.insert(_txHash, true /* placeholder value */);
     remove_WITH_LOCK(_txHash);
 }
 

libethereum/TransactionQueue.h

@@ -21,15 +21,16 @@
 
 #pragma once
 
-#include <functional>
-#include <condition_variable>
-#include <thread>
-#include <deque>
+#include "Transaction.h"
 #include <libdevcore/Common.h>
 #include <libdevcore/Guards.h>
 #include <libdevcore/Log.h>
+#include <libdevcore/LruCache.h>
 #include <libethcore/Common.h>
-#include "Transaction.h"
+#include <condition_variable>
+#include <deque>
+#include <functional>
+#include <thread>
 
 namespace dev
 {
@@ -189,7 +190,11 @@ class TransactionQueue
     h256Hash m_known;            ///< Headers of transactions in both sets.
 
     std::unordered_map<h256, std::function<void(ImportResult)>> m_callbacks;	///< Called once.
-    h256Hash m_dropped;															///< Transactions that have previously been dropped
+
+    ///< Transactions that have previously been dropped. We technically only need to store the tx
+    ///< hash, but we also store bool as a placeholder value so that we can use an LRU cache to cap
+    ///< the number of transaction hashes stored.
+    LruCache<h256, bool> m_dropped;
 
     PriorityQueue m_current;
     std::unordered_map<h256, PriorityQueue::iterator> m_currentByHash;			///< Transaction hash to set ref