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Potential Fix for stuck nodes: Don't lose future blocks if multiple future blocks received at the same height #489

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merged 6 commits into from
Nov 30, 2018
Merged

Potential Fix for stuck nodes: Don't lose future blocks if multiple future blocks received at the same height #489

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ed28dd1
Fix blockchain hang: If a future block is received at the header heig…
Nov 29, 2018
b85e21f
Fix potential for losing valid unverified blocks.
Nov 29, 2018
4142697
Merge branch 'master' into PotentiallyFixNodesGettingStuck
shargon Nov 30, 2018
9caf2e1
Fix adding to block_cache_unverified.
Nov 30, 2018
0854169
Remove unnecessary check.
Nov 30, 2018
ea77be7
Merge branch 'master' into PotentiallyFixNodesGettingStuck
erikzhang Nov 30, 2018
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31 changes: 27 additions & 4 deletions neo/Ledger/Blockchain.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -118,7 +118,7 @@ public class ImportCompleted { }
private readonly List<UInt256> header_index = new List<UInt256>();
private uint stored_header_count = 0;
private readonly Dictionary<UInt256, Block> block_cache = new Dictionary<UInt256, Block>();
private readonly Dictionary<uint, Block> block_cache_unverified = new Dictionary<uint, Block>();
private readonly Dictionary<uint, LinkedList<Block>> block_cache_unverified = new Dictionary<uint, LinkedList<Block>>();
private readonly MemoryPool mem_pool = new MemoryPool(50_000);
private readonly ConcurrentDictionary<UInt256, Transaction> mem_pool_unverified = new ConcurrentDictionary<UInt256, Transaction>();
internal readonly RelayCache RelayCache = new RelayCache(100);
Expand Down Expand Up @@ -253,6 +253,14 @@ private void OnImport(IEnumerable<Block> blocks)
Sender.Tell(new ImportCompleted());
}

private void AddUnverifiedBlockToCache(Block block)
{
if (!block_cache_unverified.TryGetValue(block.Index, out LinkedList<Block> blocks))
blocks = new LinkedList<Block>();

blocks.AddLast(block);
}

private RelayResultReason OnNewBlock(Block block)
{
if (block.Index <= Height)
Expand All @@ -261,11 +269,22 @@ private RelayResultReason OnNewBlock(Block block)
return RelayResultReason.AlreadyExists;
if (block.Index - 1 >= header_index.Count)
{
block_cache_unverified[block.Index] = block;
AddUnverifiedBlockToCache(block);
return RelayResultReason.UnableToVerify;
}
if (block.Index == header_index.Count)
{
if (block.Index > Height + 1)
{
// This could be a couple blocks ahead, and though it doesn't verify against our current
// snapshot, it may verify later. If we were to lose this block and not add it to
// block_cache_unverified here it will never be tried again because knownHashes in TaskManager
// will already have the hash so won't attempt to get the data again. (This code being missing
// is very likely why nodes were getting stuck)

AddUnverifiedBlockToCache(block);
return RelayResultReason.UnableToVerify;
}
if (!block.Verify(currentSnapshot))
return RelayResultReason.Invalid;
}
Expand Down Expand Up @@ -300,8 +319,12 @@ private RelayResultReason OnNewBlock(Block block)
system.LocalNode.Tell(new LocalNode.RelayDirectly { Inventory = block });
}
SaveHeaderHashList();
if (block_cache_unverified.TryGetValue(Height + 1, out block_persist))
Self.Tell(block_persist, ActorRefs.NoSender);

if (block_cache_unverified.TryGetValue(Height + 1, out LinkedList<Block> unverifiedBlocks))
{
foreach (var unverifiedBlock in unverifiedBlocks)
Self.Tell(unverifiedBlock, ActorRefs.NoSender);
}
}
else
{
Expand Down