tx_pool: hold off parsing a tx blob till we actually need it

src/cryptonote_core/tx_pool.cpp

@@ -927,8 +927,26 @@ namespace cryptonote
     m_transactions_lock.unlock();
   }
   //---------------------------------------------------------------------------------
-  bool tx_memory_pool::is_transaction_ready_to_go(txpool_tx_meta_t& txd, transaction &tx) const
+  bool tx_memory_pool::is_transaction_ready_to_go(txpool_tx_meta_t& txd, const cryptonote::blobdata &txblob, transaction &tx) const
   {
+    struct transction_parser
+    {
+      transction_parser(const cryptonote::blobdata &txblob, transaction &tx): txblob(txblob), tx(tx), parsed(false) {}
+      cryptonote::transaction &operator()()
+      {
+        if (!parsed)
+        {
+          if (!parse_and_validate_tx_from_blob(txblob, tx))
+            throw std::runtime_error("failed to parse transaction blob");
+          parsed = true;
+        }
+        return tx;
+      }
+      const cryptonote::blobdata &txblob;
+      transaction &tx;
+      bool parsed;
+    } lazy_tx(txblob, tx);
+
     //not the best implementation at this time, sorry :(
     //check is ring_signature already checked ?
     if(txd.max_used_block_id == null_hash)
@@ -938,7 +956,7 @@ namespace cryptonote
         return false;//we already sure that this tx is broken for this height
 
       tx_verification_context tvc;
-      if(!m_blockchain.check_tx_inputs(tx, txd.max_used_block_height, txd.max_used_block_id, tvc))
+      if(!m_blockchain.check_tx_inputs(lazy_tx(), txd.max_used_block_height, txd.max_used_block_id, tvc))
       {
         txd.last_failed_height = m_blockchain.get_current_blockchain_height()-1;
         txd.last_failed_id = m_blockchain.get_block_id_by_height(txd.last_failed_height);
@@ -955,7 +973,7 @@ namespace cryptonote
           return false;
         //check ring signature again, it is possible (with very small chance) that this transaction become again valid
         tx_verification_context tvc;
-        if(!m_blockchain.check_tx_inputs(tx, txd.max_used_block_height, txd.max_used_block_id, tvc))
+        if(!m_blockchain.check_tx_inputs(lazy_tx(), txd.max_used_block_height, txd.max_used_block_id, tvc))
         {
           txd.last_failed_height = m_blockchain.get_current_blockchain_height()-1;
           txd.last_failed_id = m_blockchain.get_block_id_by_height(txd.last_failed_height);
@@ -964,7 +982,7 @@ namespace cryptonote
       }
     }
     //if we here, transaction seems valid, but, anyway, check for key_images collisions with blockchain, just to be sure
-    if(m_blockchain.have_tx_keyimges_as_spent(tx))
+    if(m_blockchain.have_tx_keyimges_as_spent(lazy_tx()))
     {
       txd.double_spend_seen = true;
       return false;
@@ -1140,18 +1158,21 @@ namespace cryptonote
 
       cryptonote::blobdata txblob = m_blockchain.get_txpool_tx_blob(sorted_it->second);
       cryptonote::transaction tx;
-      if (!parse_and_validate_tx_from_blob(txblob, tx))
-      {
-        MERROR("Failed to parse tx from txpool");
-        sorted_it++;
-        continue;
-      }
 
       // Skip transactions that are not ready to be
       // included into the blockchain or that are
       // missing key images
       const cryptonote::txpool_tx_meta_t original_meta = meta;
-      bool ready = is_transaction_ready_to_go(meta, tx);
+      bool ready = false;
+      try
+      {
+        ready = is_transaction_ready_to_go(meta, txblob, tx);
+      }
+      catch (const std::exception &e)
+      {
+        MERROR("Failed to check transaction readiness: " << e.what());
+        // continue, not fatal
+      }
       if (memcmp(&original_meta, &meta, sizeof(meta)))
       {
         try

src/cryptonote_core/tx_pool.h

@@ -499,10 +499,12 @@ namespace cryptonote
      * @brief check if a transaction is a valid candidate for inclusion in a block
      *
      * @param txd the transaction to check (and info about it)
+     * @param txblob the transaction blob to check
+     * @param tx the parsed transaction, if successful
      *
      * @return true if the transaction is good to go, otherwise false
      */
-    bool is_transaction_ready_to_go(txpool_tx_meta_t& txd, transaction &tx) const;
+    bool is_transaction_ready_to_go(txpool_tx_meta_t& txd, const cryptonote::blobdata &txblob, transaction &tx) const;
 
     /**
      * @brief mark all transactions double spending the one passed