cryptonote_protocol_handler: sync speedup

A block queue is now placed between block download and
block processing. Blocks are now requested only from one
peer (unless starved).

Includes a new sync_info coommand.

1 files changed, 440 insertions, 128 deletions

diff --git a/src/cryptonote_protocol/cryptonote_protocol_handler.inl b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
index c5bc834ad..e3d88b353 100644
--- a/src/cryptonote_protocol/cryptonote_protocol_handler.inl
+++ b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
@@ -48,6 +48,10 @@
 
 #define MLOG_P2P_MESSAGE(x) MCINFO("net.p2p.msg", context << x)
 
+#define BLOCK_QUEUE_NBLOCKS_THRESHOLD 10 // chunks of N blocks
+#define BLOCK_QUEUE_SIZE_THRESHOLD (100*1024*1024) // MB
+#define REQUEST_NEXT_SCHEDULED_SPAN_THRESHOLD (5 * 1000000) // microseconds
+
 namespace cryptonote
 {
 
@@ -233,6 +237,8 @@ namespace cryptonote
       cnx.current_download = cntxt.m_current_speed_down / 1024;
       cnx.current_upload = cntxt.m_current_speed_up / 1024;
 
+      cnx.connection_id = cntxt.m_connection_id;
+
       connections.push_back(cnx);
 
       return true;
@@ -310,6 +316,11 @@ namespace cryptonote
     MLOG_P2P_MESSAGE("Received NOTIFY_NEW_BLOCK (hop " << arg.hop << ", " << arg.b.txs.size() << " txes)");
     if(context.m_state != cryptonote_connection_context::state_normal)
       return 1;
+    if(!is_synchronized()) // can happen if a peer connection goes to normal but another thread still hasn't finished adding queued blocks
+    {
+      LOG_DEBUG_CC(context, "Received new block while syncing, ignored");
+      return 1;
+    }
     m_core.pause_mine();
     std::list<block_complete_entry> blocks;
     blocks.push_back(arg.b);
@@ -324,6 +335,7 @@ namespace cryptonote
         m_p2p->drop_connection(context);
         m_core.cleanup_handle_incoming_blocks();
         m_core.resume_mine();
+        m_block_queue.flush_spans(context.m_connection_id);
         return 1;
       }
     }
@@ -336,6 +348,7 @@ namespace cryptonote
     {
       LOG_PRINT_CCONTEXT_L0("Block verification failed, dropping connection");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
     if(bvc.m_added_to_main_chain)
@@ -361,6 +374,11 @@ namespace cryptonote
     MLOG_P2P_MESSAGE("Received NOTIFY_NEW_FLUFFY_BLOCK (height " << arg.current_blockchain_height << ", hop " << arg.hop << ", " << arg.b.txs.size() << " txes)");
     if(context.m_state != cryptonote_connection_context::state_normal)
       return 1;
+    if(!is_synchronized()) // can happen if a peer connection goes to normal but another thread still hasn't finished adding queued blocks
+    {
+      LOG_DEBUG_CC(context, "Received new block while syncing, ignored");
+      return 1;
+    }
     
     m_core.pause_mine();
       
@@ -384,6 +402,7 @@ namespace cryptonote
           );
           
           m_p2p->drop_connection(context);
+          m_block_queue.flush_spans(context.m_connection_id);
           m_core.resume_mine();
           return 1;
         }
@@ -417,6 +436,7 @@ namespace cryptonote
               );
               
               m_p2p->drop_connection(context);
+              m_block_queue.flush_spans(context.m_connection_id);
               m_core.resume_mine();
               return 1;
             }
@@ -431,6 +451,7 @@ namespace cryptonote
             );
                         
             m_p2p->drop_connection(context);
+            m_block_queue.flush_spans(context.m_connection_id);
             m_core.resume_mine();
             return 1;
           }
@@ -455,6 +476,7 @@ namespace cryptonote
               );
               
               m_p2p->drop_connection(context);
+              m_block_queue.flush_spans(context.m_connection_id);
               m_core.resume_mine();
               return 1;
             }
@@ -472,6 +494,7 @@ namespace cryptonote
             {
               LOG_PRINT_CCONTEXT_L1("Block verification failed: transaction verification failed, dropping connection");
               m_p2p->drop_connection(context);
+              m_block_queue.flush_spans(context.m_connection_id);
               m_core.resume_mine();
               return 1;
             }
@@ -494,6 +517,7 @@ namespace cryptonote
           );
             
           m_p2p->drop_connection(context);
+          m_block_queue.flush_spans(context.m_connection_id);
           m_core.resume_mine();
           return 1;
         }
@@ -514,6 +538,7 @@ namespace cryptonote
         );
         
         m_p2p->drop_connection(context);
+        m_block_queue.flush_spans(context.m_connection_id);
         m_core.resume_mine();
         return 1;
       }      
@@ -591,6 +616,7 @@ namespace cryptonote
         {
           LOG_PRINT_CCONTEXT_L0("Block verification failed, dropping connection");
           m_p2p->drop_connection(context);
+          m_block_queue.flush_spans(context.m_connection_id);
           return 1;
         }
         if( bvc.m_added_to_main_chain )
@@ -624,6 +650,7 @@ namespace cryptonote
         
       m_core.resume_mine();
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
         
       return 1;     
     }
@@ -644,6 +671,7 @@ namespace cryptonote
     {
       LOG_ERROR_CCONTEXT("failed to find block: " << arg.block_hash << ", dropping connection");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
 
@@ -671,6 +699,7 @@ namespace cryptonote
         );
         
         m_p2p->drop_connection(context);
+        m_block_queue.flush_spans(context.m_connection_id);
         return 1;
       }
     }    
@@ -682,6 +711,7 @@ namespace cryptonote
       LOG_ERROR_CCONTEXT("Failed to handle request NOTIFY_REQUEST_FLUFFY_MISSING_TX, "
         << "failed to get requested transactions");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
     if (!missed.empty() || txs.size() != txids.size())
@@ -689,6 +719,7 @@ namespace cryptonote
       LOG_ERROR_CCONTEXT("Failed to handle request NOTIFY_REQUEST_FLUFFY_MISSING_TX, "
         << missed.size() << " requested transactions not found" << ", dropping connection");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
 
@@ -732,6 +763,7 @@ namespace cryptonote
       {
         LOG_PRINT_CCONTEXT_L1("Tx verification failed, dropping connection");
         m_p2p->drop_connection(context);
+        m_block_queue.flush_spans(context.m_connection_id);
         return 1;
       }
       if(tvc.m_should_be_relayed)
@@ -758,6 +790,8 @@ namespace cryptonote
     {
       LOG_ERROR_CCONTEXT("failed to handle request NOTIFY_REQUEST_GET_OBJECTS, dropping connection");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
+      return 1;
     }
     LOG_PRINT_CCONTEXT_L2("-->>NOTIFY_RESPONSE_GET_OBJECTS: blocks.size()=" << rsp.blocks.size() << ", txs.size()=" << rsp.txs.size()
                             << ", rsp.m_current_blockchain_height=" << rsp.current_blockchain_height << ", missed_ids.size()=" << rsp.missed_ids.size());
@@ -794,15 +828,19 @@ namespace cryptonote
   {
     MLOG_P2P_MESSAGE("Received NOTIFY_RESPONSE_GET_OBJECTS (" << arg.blocks.size() << " blocks, " << arg.txs.size() << " txes)");
 
-    // calculate size of request - mainly for logging/debug
+    bool force_next_span = false;
+
+    // calculate size of request
     size_t size = 0;
     for (auto element : arg.txs) size += element.size();
 
+    size_t blocks_size = 0;
     for (auto element : arg.blocks) {
-      size += element.block.size();
-      for (auto tx : element.txs)
-        size += tx.size();
+      blocks_size += element.block.size();
+      for (const auto &tx : element.txs)
+        blocks_size += tx.size();
     }
+    size += blocks_size;
 
     for (auto element : arg.missed_ids)
       size += sizeof(element.data);
@@ -819,6 +857,8 @@ namespace cryptonote
         m_avg_buffer.erase_end(1);
       } while(dbg_poke_lock && (dbg_repeat++)<100000); // in debug/poke mode, repeat this calculation to trigger hidden locking error if there is one
     }
+    MDEBUG(context << " downloaded " << size << " bytes worth of blocks");
+
     /*using namespace boost::chrono;
       auto point = steady_clock::now();
       auto time_from_epoh = point.time_since_epoch();
@@ -831,14 +871,17 @@ namespace cryptonote
       LOG_ERROR_CCONTEXT("sent wrong NOTIFY_HAVE_OBJECTS: arg.m_current_blockchain_height=" << arg.current_blockchain_height
         << " < m_last_response_height=" << context.m_last_response_height << ", dropping connection");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
 
     context.m_remote_blockchain_height = arg.current_blockchain_height;
 
-    size_t count = 0;
     std::vector<crypto::hash> block_hashes;
     block_hashes.reserve(arg.blocks.size());
+    const boost::posix_time::ptime now = boost::posix_time::microsec_clock::universal_time();
+    uint64_t start_height = std::numeric_limits<uint64_t>::max();
+    cryptonote::block b;
     for(const block_complete_entry& block_entry: arg.blocks)
     {
       if (m_stopping)
@@ -846,35 +889,33 @@ namespace cryptonote
         return 1;
       }
 
-      ++count;
-      block b;
       if(!parse_and_validate_block_from_blob(block_entry.block, b))
       {
         LOG_ERROR_CCONTEXT("sent wrong block: failed to parse and validate block: "
           << epee::string_tools::buff_to_hex_nodelimer(block_entry.block) << ", dropping connection");
         m_p2p->drop_connection(context);
+        m_block_queue.flush_spans(context.m_connection_id);
         return 1;
       }
-      //to avoid concurrency in core between connections, suspend connections which delivered block later then first one
-      const crypto::hash block_hash = get_block_hash(b);
-      if(count == 2)
+      if (b.miner_tx.vin.size() != 1 || b.miner_tx.vin.front().type() != typeid(txin_gen))
       {
-        if(m_core.have_block(block_hash))
-        {
-          context.m_state = cryptonote_connection_context::state_idle;
-          context.m_needed_objects.clear();
-          context.m_requested_objects.clear();
-          LOG_PRINT_CCONTEXT_L1("Connection set to idle state.");
-          return 1;
-        }
+        LOG_ERROR_CCONTEXT("sent wrong block: block: miner tx does not have exactly one txin_gen input"
+          << epee::string_tools::buff_to_hex_nodelimer(block_entry.block) << ", dropping connection");
+        m_p2p->drop_connection(context);
+        m_block_queue.flush_spans(context.m_connection_id);
+        return 1;
       }
+      if (start_height == std::numeric_limits<uint64_t>::max())
+        start_height = boost::get<txin_gen>(b.miner_tx.vin[0]).height;
 
+      const crypto::hash block_hash = get_block_hash(b);
       auto req_it = context.m_requested_objects.find(block_hash);
       if(req_it == context.m_requested_objects.end())
       {
         LOG_ERROR_CCONTEXT("sent wrong NOTIFY_RESPONSE_GET_OBJECTS: block with id=" << epee::string_tools::pod_to_hex(get_blob_hash(block_entry.block))
           << " wasn't requested, dropping connection");
         m_p2p->drop_connection(context);
+        m_block_queue.flush_spans(context.m_connection_id);
         return 1;
       }
       if(b.tx_hashes.size() != block_entry.txs.size())
@@ -882,6 +923,7 @@ namespace cryptonote
         LOG_ERROR_CCONTEXT("sent wrong NOTIFY_RESPONSE_GET_OBJECTS: block with id=" << epee::string_tools::pod_to_hex(get_blob_hash(block_entry.block))
           << ", tx_hashes.size()=" << b.tx_hashes.size() << " mismatch with block_complete_entry.m_txs.size()=" << block_entry.txs.size() << ", dropping connection");
         m_p2p->drop_connection(context);
+        m_block_queue.flush_spans(context.m_connection_id);
         return 1;
       }
 
@@ -894,114 +936,186 @@ namespace cryptonote
       MERROR("returned not all requested objects (context.m_requested_objects.size()="
         << context.m_requested_objects.size() << "), dropping connection");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
 
+    // get the last parsed block, which should be the highest one
+    if(m_core.have_block(cryptonote::get_block_hash(b)))
+    {
+      const uint64_t subchain_height = start_height + arg.blocks.size();
+      LOG_DEBUG_CC(context, "These are old blocks, ignoring: blocks " << start_height << " - " << (subchain_height-1) << ", blockchain height " << m_core.get_current_blockchain_height());
+      goto skip;
+    }
 
     {
       MLOG_YELLOW(el::Level::Debug, "Got NEW BLOCKS inside of " << __FUNCTION__ << ": size: " << arg.blocks.size());
 
+      // add that new span to the block queue
+      const boost::posix_time::time_duration dt = now - context.m_last_request_time;
+      const float rate = size * 1e6 / (dt.total_microseconds() + 1);
+      MDEBUG(context << " adding span: " << arg.blocks.size() << " at height " << start_height << ", " << dt.total_microseconds()/1e6 << " seconds, " << (rate/1e3) << " kB/s, size now " << (m_block_queue.get_data_size() + blocks_size) / 1048576.f << " MB");
+      m_block_queue.add_blocks(start_height, arg.blocks, context.m_connection_id, rate, blocks_size);
+
       if (m_core.get_test_drop_download() && m_core.get_test_drop_download_height()) { // DISCARD BLOCKS for testing
 
-        // we lock all the rest to avoid having multiple connections redo a lot
-        // of the same work, and one of them doing it for nothing: subsequent
-        // connections will wait until the current one's added its blocks, then
-        // will add any extra it has, if any
-        CRITICAL_REGION_LOCAL(m_sync_lock);
+        // We try to lock the sync lock. If we can, it means no other thread is
+        // currently adding blocks, so we do that for as long as we can from the
+        // block queue. Then, we go back to download.
+        const boost::unique_lock<boost::mutex> sync{m_sync_lock, boost::try_to_lock};
+        if (!sync.owns_lock())
+        {
+          MINFO("Failed to lock m_sync_lock, going back to download");
+          goto skip;
+        }
+        MDEBUG(context << " lock m_sync_lock, adding blocks to chain...");
 
         m_core.pause_mine();
         epee::misc_utils::auto_scope_leave_caller scope_exit_handler = epee::misc_utils::create_scope_leave_handler(
           boost::bind(&t_core::resume_mine, &m_core));
 
-        const uint64_t previous_height = m_core.get_current_blockchain_height();
-
-        // dismiss what another connection might already have done (likely everything)
-        uint64_t top_height;
-        crypto::hash top_hash;
-        if (m_core.get_blockchain_top(top_height, top_hash)) {
-          uint64_t dismiss = 1;
-          for (const auto &h: block_hashes) {
-            if (top_hash == h) {
-              LOG_DEBUG_CC(context, "Found current top block in synced blocks, dismissing "
-                  << dismiss << "/" << arg.blocks.size() << " blocks");
-              while (dismiss--)
-                arg.blocks.pop_front();
-              break;
-            }
-            ++dismiss;
+        while (1)
+        {
+          const uint64_t previous_height = m_core.get_current_blockchain_height();
+          uint64_t start_height;
+          std::list<cryptonote::block_complete_entry> blocks;
+          boost::uuids::uuid span_connection_id;
+          m_block_queue.mark_last_block(previous_height - 1);
+          if (!m_block_queue.get_next_span(start_height, blocks, span_connection_id))
+          {
+            MDEBUG(context << " no next span found, going back to download");
+            break;
+          }
+          MDEBUG(context << " next span in the queue has blocks " << start_height << "-" << (start_height + blocks.size() - 1)
+              << ", we need " << previous_height);
+          if (previous_height < start_height || previous_height >= start_height + blocks.size())
+          {
+            MDEBUG(context << " this span is not what we need, going back to download");
+            break;
           }
-        }
 
-        if (arg.blocks.empty())
-          goto skip;
+          const boost::posix_time::ptime start = boost::posix_time::microsec_clock::universal_time();
 
-        m_core.prepare_handle_incoming_blocks(arg.blocks);
+          m_core.prepare_handle_incoming_blocks(blocks);
 
-        for(const block_complete_entry& block_entry: arg.blocks)
-        {
-          if (m_stopping)
+          uint64_t block_process_time_full = 0, transactions_process_time_full = 0;
+          for(const block_complete_entry& block_entry: blocks)
           {
-              m_core.cleanup_handle_incoming_blocks();
-              return 1;
-          }
+            if (m_stopping)
+            {
+                m_core.cleanup_handle_incoming_blocks();
+                return 1;
+            }
 
-          // process transactions
-          TIME_MEASURE_START(transactions_process_time);
-          for(auto& tx_blob: block_entry.txs)
-          {
-            tx_verification_context tvc = AUTO_VAL_INIT(tvc);
-            m_core.handle_incoming_tx(tx_blob, tvc, true, true, false);
-            if(tvc.m_verifivation_failed)
+            // process transactions
+            TIME_MEASURE_START(transactions_process_time);
+            for(auto& tx_blob: block_entry.txs)
             {
-              LOG_ERROR_CCONTEXT("transaction verification failed on NOTIFY_RESPONSE_GET_OBJECTS, tx_id = "
-                  << epee::string_tools::pod_to_hex(get_blob_hash(tx_blob)) << ", dropping connection");
-              m_p2p->drop_connection(context);
+              tx_verification_context tvc = AUTO_VAL_INIT(tvc);
+              m_core.handle_incoming_tx(tx_blob, tvc, true, true, false);
+              if(tvc.m_verifivation_failed)
+              {
+                if (!m_p2p->for_connection(span_connection_id, [&](cryptonote_connection_context& context, nodetool::peerid_type peer_id, uint32_t f)->bool{
+                  LOG_ERROR_CCONTEXT("transaction verification failed on NOTIFY_RESPONSE_GET_OBJECTS, tx_id = "
+                      << epee::string_tools::pod_to_hex(get_blob_hash(tx_blob)) << ", dropping connection");
+                  m_p2p->drop_connection(context);
+                  m_block_queue.flush_spans(context.m_connection_id, true);
+                  return true;
+                }))
+                  LOG_ERROR_CCONTEXT("span connection id not found");
+
+                m_core.cleanup_handle_incoming_blocks();
+                // in case the peer had dropped beforehand, remove the span anyway so other threads can wake up and get it
+                m_block_queue.remove_spans(span_connection_id, start_height);
+                return 1;
+              }
+            }
+            TIME_MEASURE_FINISH(transactions_process_time);
+            transactions_process_time_full += transactions_process_time;
+
+            // process block
+
+            TIME_MEASURE_START(block_process_time);
+            block_verification_context bvc = boost::value_initialized<block_verification_context>();
+
+            m_core.handle_incoming_block(block_entry.block, bvc, false); // <--- process block
+
+            if(bvc.m_verifivation_failed)
+            {
+              if (!m_p2p->for_connection(span_connection_id, [&](cryptonote_connection_context& context, nodetool::peerid_type peer_id, uint32_t f)->bool{
+                LOG_PRINT_CCONTEXT_L1("Block verification failed, dropping connection");
+                m_p2p->drop_connection(context);
+                m_p2p->add_host_fail(context.m_remote_address);
+                m_block_queue.flush_spans(context.m_connection_id, true);
+                return true;
+              }))
+                LOG_ERROR_CCONTEXT("span connection id not found");
+
               m_core.cleanup_handle_incoming_blocks();
+              // in case the peer had dropped beforehand, remove the span anyway so other threads can wake up and get it
+              m_block_queue.remove_spans(span_connection_id, start_height);
               return 1;
             }
-          }
-          TIME_MEASURE_FINISH(transactions_process_time);
+            if(bvc.m_marked_as_orphaned)
+            {
+              if (!m_p2p->for_connection(span_connection_id, [&](cryptonote_connection_context& context, nodetool::peerid_type peer_id, uint32_t f)->bool{
+                LOG_PRINT_CCONTEXT_L1("Block received at sync phase was marked as orphaned, dropping connection");
+                m_p2p->drop_connection(context);
+                m_p2p->add_host_fail(context.m_remote_address);
+                m_block_queue.flush_spans(context.m_connection_id, true);
+                return true;
+              }))
+                LOG_ERROR_CCONTEXT("span connection id not found");
 
-          // process block
+              m_core.cleanup_handle_incoming_blocks();
+              // in case the peer had dropped beforehand, remove the span anyway so other threads can wake up and get it
+              m_block_queue.remove_spans(span_connection_id, start_height);
+              return 1;
+            }
 
-          TIME_MEASURE_START(block_process_time);
-          block_verification_context bvc = boost::value_initialized<block_verification_context>();
+            TIME_MEASURE_FINISH(block_process_time);
+            block_process_time_full += block_process_time;
 
-          m_core.handle_incoming_block(block_entry.block, bvc, false); // <--- process block
+          } // each download block
 
-          if(bvc.m_verifivation_failed)
-          {
-            LOG_PRINT_CCONTEXT_L1("Block verification failed, dropping connection");
-            m_p2p->drop_connection(context);
-            m_p2p->add_host_fail(context.m_remote_address);
-            m_core.cleanup_handle_incoming_blocks();
-            return 1;
-          }
-          if(bvc.m_marked_as_orphaned)
-          {
-            LOG_PRINT_CCONTEXT_L1("Block received at sync phase was marked as orphaned, dropping connection");
-            m_p2p->drop_connection(context);
-            m_p2p->add_host_fail(context.m_remote_address);
-            m_core.cleanup_handle_incoming_blocks();
-            return 1;
-          }
+          LOG_PRINT_CCONTEXT_L2("Block process time (" << blocks.size() << " blocks): " << block_process_time_full + transactions_process_time_full << " (" << transactions_process_time_full << "/" << block_process_time_full << ") ms");
 
-          TIME_MEASURE_FINISH(block_process_time);
-          LOG_PRINT_CCONTEXT_L2("Block process time: " << block_process_time + transactions_process_time << "(" << transactions_process_time << "/" << block_process_time << ")ms");
+          m_core.cleanup_handle_incoming_blocks();
 
-        } // each download block
-        m_core.cleanup_handle_incoming_blocks();
+          m_block_queue.mark_last_block(m_core.get_current_blockchain_height() - 1);
 
-        if (m_core.get_current_blockchain_height() > previous_height)
-        {
-          MGINFO_YELLOW(context << " Synced " << m_core.get_current_blockchain_height() << "/" << m_core.get_target_blockchain_height());
+          if (m_core.get_current_blockchain_height() > previous_height)
+          {
+            const boost::posix_time::time_duration dt = boost::posix_time::microsec_clock::universal_time() - start;
+            std::string timing_message = "";
+            if (ELPP->vRegistry()->allowed(el::Level::Info, "sync-info"))
+              timing_message = std::string(" (") + std::to_string(dt.total_microseconds()/1e6) + " sec, "
+                + std::to_string((m_core.get_current_blockchain_height() - previous_height) * 1e6 / dt.total_microseconds())
+                + " blocks/sec), " + std::to_string(m_block_queue.get_data_size() / 1048576.f) + " MB queued";
+            if (ELPP->vRegistry()->allowed(el::Level::Debug, "sync-info"))
+              timing_message += std::string(": ") + m_block_queue.get_overview();
+            MGINFO_YELLOW(context << " Synced " << m_core.get_current_blockchain_height() << "/" << m_core.get_target_blockchain_height()
+                << timing_message);
+          }
         }
       } // if not DISCARD BLOCK
 
-
+      if (should_download_next_span(context))
+      {
+        context.m_needed_objects.clear();
+        context.m_last_response_height = 0;
+        force_next_span = true;
+      }
     }
+
 skip:
-    request_missing_objects(context, true);
+    if (!request_missing_objects(context, true, force_next_span))
+    {
+      LOG_ERROR_CCONTEXT("Failed to request missing objects, dropping connection");
+      m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
+      return 1;
+    }
     return 1;
   }
   //------------------------------------------------------------------------------------------------------------------------
@@ -1020,6 +1134,7 @@ skip:
     {
       LOG_ERROR_CCONTEXT("Failed to handle NOTIFY_REQUEST_CHAIN.");
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
     LOG_PRINT_CCONTEXT_L2("-->>NOTIFY_RESPONSE_CHAIN_ENTRY: m_start_height=" << r.start_height << ", m_total_height=" << r.total_height << ", m_block_ids.size()=" << r.m_block_ids.size());
@@ -1028,54 +1143,252 @@ skip:
   }
   //------------------------------------------------------------------------------------------------------------------------
   template<class t_core>
-  bool t_cryptonote_protocol_handler<t_core>::request_missing_objects(cryptonote_connection_context& context, bool check_having_blocks)
+  bool t_cryptonote_protocol_handler<t_core>::should_download_next_span(cryptonote_connection_context& context) const
   {
-    //if (!m_one_request == false)
-      //return true;
-    m_one_request = false;
-    // save request size to log (dr monero)
-    /*using namespace boost::chrono;
-      auto point = steady_clock::now();
-      auto time_from_epoh = point.time_since_epoch();
-      auto sec = duration_cast< seconds >( time_from_epoh ).count();*/
+    std::list<crypto::hash> hashes;
+    boost::uuids::uuid span_connection_id;
+    boost::posix_time::ptime request_time;
+    std::pair<uint64_t, uint64_t> span = m_block_queue.get_next_span_if_scheduled(hashes, span_connection_id, request_time);
 
-    if(context.m_needed_objects.size())
+    // if the next span is not scheduled (or there is none)
+    if (span.second == 0)
+    {
+      // we might be in a weird case where there is a filled next span,
+      // but it starts higher than the current height
+      uint64_t height;
+      std::list<cryptonote::block_complete_entry> bcel;
+      if (!m_block_queue.get_next_span(height, bcel, span_connection_id, true))
+        return false;
+      if (height > m_core.get_current_blockchain_height())
+      {
+        MDEBUG(context << " we should download it as the next block isn't scheduled");
+        return true;
+      }
+      return false;
+    }
+    // if it was scheduled by this particular peer
+    if (span_connection_id == context.m_connection_id)
+      return false;
+
+    float span_speed = m_block_queue.get_speed(span_connection_id);
+    float speed = m_block_queue.get_speed(context.m_connection_id);
+    MDEBUG(context << " next span is scheduled for " << span_connection_id << ", speed " << span_speed << ", ours " << speed);
+
+    // we try for that span too if:
+    //  - we're substantially faster, or:
+    //  - we're the fastest and the other one isn't (avoids a peer being waaaay slow but yet unmeasured)
+    //  - the other one asked at least 5 seconds ago
+    if (span_speed < .25 && speed > .75f)
+    {
+      MDEBUG(context << " we should download it as we're substantially faster");
+      return true;
+    }
+    if (speed == 1.0f && span_speed != 1.0f)
+    {
+      MDEBUG(context << " we should download it as we're the fastest peer");
+      return true;
+    }
+    const boost::posix_time::ptime now = boost::posix_time::microsec_clock::universal_time();
+    if ((now - request_time).total_microseconds() > REQUEST_NEXT_SCHEDULED_SPAN_THRESHOLD)
+    {
+      MDEBUG(context << " we should download it as this span was requested long ago");
+      return true;
+    }
+    return false;
+  }
+  //------------------------------------------------------------------------------------------------------------------------
+  template<class t_core>
+  bool t_cryptonote_protocol_handler<t_core>::request_missing_objects(cryptonote_connection_context& context, bool check_having_blocks, bool force_next_span)
+  {
+    m_block_queue.mark_last_block(m_core.get_current_blockchain_height() - 1);
+
+    // if we don't need to get next span, and the block queue is full enough, wait a bit
+    bool start_from_current_chain = false;
+    if (!force_next_span)
+    {
+      bool first = true;
+      while (1)
+      {
+        size_t nblocks = m_block_queue.get_num_filled_spans();
+        size_t size = m_block_queue.get_data_size();
+        if (nblocks < BLOCK_QUEUE_NBLOCKS_THRESHOLD || size < BLOCK_QUEUE_SIZE_THRESHOLD)
+        {
+          if (!first)
+          {
+            LOG_DEBUG_CC(context, "Block queue is " << nblocks << " and " << size << ", resuming");
+          }
+          break;
+        }
+
+        if (should_download_next_span(context))
+        {
+          MDEBUG(context << " we should try for that next span too, we think we could get it faster, resuming");
+          force_next_span = true;
+          break;
+        }
+
+        if (first)
+        {
+          LOG_DEBUG_CC(context, "Block queue is " << nblocks << " and " << size << ", pausing");
+          first = false;
+        }
+        for (size_t n = 0; n < 50; ++n)
+        {
+          if (m_stopping)
+            return 1;
+          boost::this_thread::sleep_for(boost::chrono::milliseconds(100));
+        }
+      }
+    }
+
+    MDEBUG(context << " request_missing_objects: check " << check_having_blocks << ", force_next_span " << force_next_span << ", m_needed_objects " << context.m_needed_objects.size() << " lrh " << context.m_last_response_height << ", chain " << m_core.get_current_blockchain_height());
+    if(context.m_needed_objects.size() || force_next_span)
     {
       //we know objects that we need, request this objects
       NOTIFY_REQUEST_GET_OBJECTS::request req;
+      bool is_next = false;
       size_t count = 0;
-      auto it = context.m_needed_objects.begin();
-
       const size_t count_limit = m_core.get_block_sync_size();
-      MDEBUG("Setting count_limit: " << count_limit);
-      while(it != context.m_needed_objects.end() && count < count_limit)
+      std::pair<uint64_t, uint64_t> span = std::make_pair(0, 0);
+      if (force_next_span)
       {
-        if( !(check_having_blocks && m_core.have_block(*it)))
+        MDEBUG(context << " force_next_span is true, trying next span");
+        span = m_block_queue.get_start_gap_span();
+        if (span.second > 0)
         {
-          req.blocks.push_back(*it);
-          ++count;
-          context.m_requested_objects.insert(*it);
+          const uint64_t first_block_height_known = context.m_last_response_height - context.m_needed_objects.size() + 1;
+          const uint64_t last_block_height_known = context.m_last_response_height;
+          const uint64_t first_block_height_needed = span.first;
+          const uint64_t last_block_height_needed = span.first + std::min(span.second, (uint64_t)count_limit) - 1;
+          MDEBUG(context << " gap found, span: " << span.first << " - " << span.first + span.second - 1 << " (" << last_block_height_needed << ")");
+          MDEBUG(context << " current known hashes from from " << first_block_height_known << " to " << last_block_height_known);
+          if (first_block_height_needed < first_block_height_known || last_block_height_needed > last_block_height_known)
+          {
+            MDEBUG(context << " we are missing some of the necessary hashes for this gap, requesting chain again");
+            context.m_needed_objects.clear();
+            context.m_last_response_height = 0;
+            start_from_current_chain = true;
+            goto skip;
+          }
+          MDEBUG(context << " we have the hashes for this gap");
+        }
+        if (span.second == 0)
+        {
+          std::list<crypto::hash> hashes;
+          boost::uuids::uuid span_connection_id;
+          boost::posix_time::ptime time;
+          span = m_block_queue.get_next_span_if_scheduled(hashes, span_connection_id, time);
+          if (span.second > 0)
+          {
+            is_next = true;
+            for (const auto &hash: hashes)
+            {
+              req.blocks.push_back(hash);
+              context.m_requested_objects.insert(hash);
+            }
+          }
         }
-        context.m_needed_objects.erase(it++);
       }
-      LOG_PRINT_CCONTEXT_L1("-->>NOTIFY_REQUEST_GET_OBJECTS: blocks.size()=" << req.blocks.size() << ", txs.size()=" << req.txs.size()
-          << "requested blocks count=" << count << " / " << count_limit);
-      //epee::net_utils::network_throttle_manager::get_global_throttle_inreq().logger_handle_net("log/dr-monero/net/req-all.data", sec, get_avg_block_size());
+      if (span.second == 0)
+      {
+        MDEBUG(context << " span size is 0");
+        if (context.m_last_response_height + 1 < context.m_needed_objects.size())
+        {
+          MERROR(context << " ERROR: inconsistent context: lrh " << context.m_last_response_height << ", nos " << context.m_needed_objects.size());
+          context.m_needed_objects.clear();
+          context.m_last_response_height = 0;
+          goto skip;
+        }
+        const uint64_t first_block_height = context.m_last_response_height - context.m_needed_objects.size() + 1;
+        span = m_block_queue.reserve_span(first_block_height, context.m_last_response_height, count_limit, context.m_connection_id);
+        MDEBUG(context << " span from " << first_block_height << ": " << span.first << "/" << span.second);
+      }
+      if (span.second == 0 && !force_next_span)
+      {
+        MDEBUG(context << " still no span reserved, we may be in the corner case of next span scheduled and everything else scheduled/filled");
+        std::list<crypto::hash> hashes;
+        boost::uuids::uuid span_connection_id;
+        boost::posix_time::ptime time;
+        span = m_block_queue.get_next_span_if_scheduled(hashes, span_connection_id, time);
+        if (span.second > 0)
+        {
+          is_next = true;
+          for (const auto &hash: hashes)
+          {
+            req.blocks.push_back(hash);
+            context.m_requested_objects.insert(hash);
+          }
+        }
+      }
+      MDEBUG(context << " span: " << span.first << "/" << span.second << " (" << span.first << " - " << (span.first + span.second - 1) << ")");
+      if (span.second > 0)
+      {
+        if (!is_next)
+        {
+          const uint64_t first_context_block_height = context.m_last_response_height - context.m_needed_objects.size() + 1;
+          uint64_t skip = span.first - first_context_block_height;
+          if (skip > context.m_needed_objects.size())
+          {
+            MERROR("ERROR: skip " << skip << ", m_needed_objects " << context.m_needed_objects.size() << ", first_context_block_height" << first_context_block_height);
+            return false;
+          }
+          while (skip--)
+            context.m_needed_objects.pop_front();
+          if (context.m_needed_objects.size() < span.second)
+          {
+            MERROR("ERROR: span " << span.first << "/" << span.second << ", m_needed_objects " << context.m_needed_objects.size());
+            return false;
+          }
+
+          std::list<crypto::hash> hashes;
+          auto it = context.m_needed_objects.begin();
+          for (size_t n = 0; n < span.second; ++n)
+          {
+            req.blocks.push_back(*it);
+            ++count;
+            context.m_requested_objects.insert(*it);
+            hashes.push_back(*it);
+            auto j = it++;
+            context.m_needed_objects.erase(j);
+          }
+
+          m_block_queue.set_span_hashes(span.first, context.m_connection_id, hashes);
+        }
+
+        context.m_last_request_time = boost::posix_time::microsec_clock::universal_time();
+        LOG_PRINT_CCONTEXT_L1("-->>NOTIFY_REQUEST_GET_OBJECTS: blocks.size()=" << req.blocks.size() << ", txs.size()=" << req.txs.size()
+            << "requested blocks count=" << count << " / " << count_limit << " from " << span.first);
+        //epee::net_utils::network_throttle_manager::get_global_throttle_inreq().logger_handle_net("log/dr-monero/net/req-all.data", sec, get_avg_block_size());
+
+        post_notify<NOTIFY_REQUEST_GET_OBJECTS>(req, context);
+        return true;
+      }
+    }
 
-      post_notify<NOTIFY_REQUEST_GET_OBJECTS>(req, context);
-    }else if(context.m_last_response_height < context.m_remote_blockchain_height-1)
+skip:
+    context.m_needed_objects.clear();
+    if(context.m_last_response_height < context.m_remote_blockchain_height-1)
     {//we have to fetch more objects ids, request blockchain entry
 
       NOTIFY_REQUEST_CHAIN::request r = boost::value_initialized<NOTIFY_REQUEST_CHAIN::request>();
       m_core.get_short_chain_history(r.block_ids);
+
+      if (!start_from_current_chain)
+      {
+        // we'll want to start off from where we are on the download side, which may not be added yet
+        crypto::hash last_known_hash = m_block_queue.get_last_known_hash();
+        if (last_known_hash != cryptonote::null_hash && r.block_ids.front() != last_known_hash)
+          r.block_ids.push_front(last_known_hash);
+      }
+
       handler_request_blocks_history( r.block_ids ); // change the limit(?), sleep(?)
 
       //std::string blob; // for calculate size of request
       //epee::serialization::store_t_to_binary(r, blob);
       //epee::net_utils::network_throttle_manager::get_global_throttle_inreq().logger_handle_net("log/dr-monero/net/req-all.data", sec, get_avg_block_size());
-      LOG_PRINT_CCONTEXT_L1("r = " << 200);
+      //LOG_PRINT_CCONTEXT_L1("r = " << 200);
 
-      LOG_PRINT_CCONTEXT_L1("-->>NOTIFY_REQUEST_CHAIN: m_block_ids.size()=" << r.block_ids.size() );
+      LOG_PRINT_CCONTEXT_L1("-->>NOTIFY_REQUEST_CHAIN: m_block_ids.size()=" << r.block_ids.size() << ", start_from_current_chain " << start_from_current_chain);
       post_notify<NOTIFY_REQUEST_CHAIN>(r, context);
     }else
     {
@@ -1134,15 +1447,7 @@ skip:
       LOG_ERROR_CCONTEXT("sent empty m_block_ids, dropping connection");
       m_p2p->drop_connection(context);
       m_p2p->add_host_fail(context.m_remote_address);
-      return 1;
-    }
-
-    if(!m_core.have_block(arg.m_block_ids.front()))
-    {
-      LOG_ERROR_CCONTEXT("sent m_block_ids starting from unknown id: "
-                                              << epee::string_tools::pod_to_hex(arg.m_block_ids.front()) << " , dropping connection");
-      m_p2p->drop_connection(context);
-      m_p2p->add_host_fail(context.m_remote_address);
+      m_block_queue.flush_spans(context.m_connection_id);
       return 1;
     }
 
@@ -1154,15 +1459,22 @@ skip:
                                                                          << ", m_start_height=" << arg.start_height
                                                                          << ", m_block_ids.size()=" << arg.m_block_ids.size());
       m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
+      return 1;
     }
 
     for(auto& bl_id: arg.m_block_ids)
     {
-      if(!m_core.have_block(bl_id))
-        context.m_needed_objects.push_back(bl_id);
+      context.m_needed_objects.push_back(bl_id);
     }
 
-    request_missing_objects(context, false);
+    if (!request_missing_objects(context, false))
+    {
+      LOG_ERROR_CCONTEXT("Failed to request missing objects, dropping connection");
+      m_p2p->drop_connection(context);
+      m_block_queue.flush_spans(context.m_connection_id);
+      return 1;
+    }
     return 1;
   }
   //------------------------------------------------------------------------------------------------------------------------