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🧹 Remove Fork() and Swap() #3948

Merged
merged 9 commits into from
Sep 6, 2024
Merged

🧹 Remove Fork() and Swap() #3948

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c8b77a8
Simplified branch appending
greymistcube Sep 5, 2024
a3f9469
Removed invalidated test
greymistcube Sep 5, 2024
716098d
Simplified branch appending; removed usage of Swap()
greymistcube Sep 5, 2024
3440544
Removed irrelevant tests
greymistcube Sep 5, 2024
ef45a2a
Cleanup Swap() and Fork()
greymistcube Sep 5, 2024
9fa4ebd
Removed Swap()
greymistcube Sep 5, 2024
f7ed600
Removed Fork()
greymistcube Sep 5, 2024
eb170de
Refactored AppendBranch() to allow cancellation
greymistcube Sep 5, 2024
38e8381
Changelog
greymistcube Sep 6, 2024
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2 changes: 2 additions & 0 deletions CHANGES.md
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ To be released.
[[#3942]]
- (Libplanet.Net) Changed `BlockHashDownloadState` and `BlockDownloadState`
to be `Obsolete`. [[#3943]]
- Removed `Fork()` method from `BlockChain`. [[#3948]]

### Backward-incompatible network protocol changes

Expand Down Expand Up @@ -55,6 +56,7 @@ To be released.
[#3934]: https://github.com/planetarium/libplanet/pull/3934
[#3942]: https://github.com/planetarium/libplanet/pull/3942
[#3943]: https://github.com/planetarium/libplanet/pull/3943
[#3948]: https://github.com/planetarium/libplanet/pull/3948


Version 5.2.2
Expand Down
214 changes: 29 additions & 185 deletions src/Libplanet.Net/Swarm.BlockCandidate.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,8 +64,6 @@ private bool BlockCandidateProcess(
IProgress<BlockSyncState> progress,
CancellationToken cancellationToken)
{
BlockChain synced = null;
System.Action renderSwap = () => { };
try
{
FillBlocksAsyncStarted.Set();
Expand All @@ -74,17 +72,19 @@ private bool BlockCandidateProcess(
nameof(BlockCandidateProcess),
BlockChain.Tip.Index,
BlockChain.Tip.Hash);
synced = AppendPreviousBlocks(
AppendBranch(
blockChain: BlockChain,
candidate: candidate,
render: render,
progress: progress);
progress: progress,
cancellationToken: cancellationToken);
ProcessFillBlocksFinished.Set();
_logger.Debug(
"{MethodName}() finished appending blocks; synced tip is #{Index} {Hash}",
"{MethodName}() finished appending blocks; current tip is #{Index} {Hash}",
nameof(BlockCandidateProcess),
synced.Tip.Index,
synced.Tip.Hash);
BlockChain.Tip.Index,
BlockChain.Tip.Hash);
return true;
}
catch (Exception e)
{
Expand All @@ -95,107 +95,24 @@ private bool BlockCandidateProcess(
FillBlocksAsyncFailed.Set();
return false;
}

try
{
// Although highly unlikely, current block chain's tip can change.
if (synced is { } syncedB
&& !syncedB.Id.Equals(BlockChain?.Id)
&& BlockChain.Tip.Index < syncedB.Tip.Index)
{
_logger.Debug(
"Swapping chain {ChainIdA} with chain {ChainIdB}...",
BlockChain.Id,
synced.Id
);
renderSwap = BlockChain.Swap(
synced,
render: render);
_logger.Debug(
"Swapped chain {ChainIdA} with chain {ChainIdB}",
BlockChain.Id,
synced.Id
);

renderSwap();
BroadcastBlock(BlockChain.Tip);
return true;
}
else
{
return false;
}
}
catch (Exception e)
{
_logger.Error(
e,
"{MethodName}() has failed to swap chain {ChainIdA} with chain {ChainIdB}",
nameof(BlockCandidateProcess),
BlockChain.Id,
synced.Id);
return false;
}
}

private BlockChain AppendPreviousBlocks(
private void AppendBranch(
BlockChain blockChain,
Branch candidate,
bool render,
IProgress<BlockSyncState> progress)
IProgress<BlockSyncState> progress,
CancellationToken cancellationToken = default)
{
BlockChain workspace;
List<Guid> scope = new List<Guid>();
bool forked = false;

Block oldTip = blockChain.Tip;
List<(Block, BlockCommit)> blocks = candidate.Blocks.ToList();
Block branchpoint = FindBranchpoint(
oldTip,
blocks.Select(pair => pair.Item1).ToList());
Block branchpoint = oldTip;
List<(Block, BlockCommit)> blocks = ExtractBlocksToAppend(branchpoint, candidate);

if (branchpoint.Equals(oldTip))
if (!blocks.Any())
{
_logger.Debug(
"No need to fork. at {MethodName}()",
nameof(AppendPreviousBlocks));
workspace = blockChain;
}
else if (!blockChain.ContainsBlock(branchpoint.Hash))
{
// FIXME: This behavior can unexpectedly terminate the swarm (and the game
// app) if it encounters a peer having a different blockchain, and therefore
// can be exploited to remotely shut down other nodes as well.
// Since the intention of this behavior is to prevent mistakes to try to
// connect incorrect seeds (by a user), this behavior should be limited for
// only seed peers.
var msg =
$"Since the genesis block is fixed to {BlockChain.Genesis} " +
"protocol-wise, the blockchain which does not share " +
"any mutual block is not acceptable.";
throw new InvalidGenesisBlockException(
msg,
branchpoint.Hash,
blockChain.Genesis.Hash);
}
else
{
_logger.Debug(
"Trying to fork... at {MethodName}()",
nameof(AppendPreviousBlocks)
);
workspace = blockChain.Fork(branchpoint.Hash);
forked = true;
scope.Add(workspace.Id);
_logger.Debug(
"Fork finished. at {MethodName}()",
nameof(AppendPreviousBlocks)
);
}

if (!workspace.Tip.Hash.Equals(blocks.First().Item1.PreviousHash))
{
blocks = blocks.Skip(1).ToList();
"There are no blocks to append to block {BlockHash}",
branchpoint.Hash);
}

try
Expand All @@ -204,14 +121,14 @@ private BlockChain AppendPreviousBlocks(

foreach (var (block, commit) in blocks)
{
cancellationToken.ThrowIfCancellationRequested();
if (block.ProtocolVersion < BlockMetadata.SlothProtocolVersion)
{
workspace.AppendStateRootHashPreceded(
block, commit, render: render && !forked);
blockChain.AppendStateRootHashPreceded(block, commit, render: render);
}
else
{
workspace.Append(block, commit, render: render && !forked);
blockChain.Append(block, commit, render: render);
}

verifiedBlockCount++;
Expand All @@ -233,102 +150,29 @@ private BlockChain AppendPreviousBlocks(
}
catch (Exception e)
{
const string dbgMsg =
"An exception occurred while appending a block " +
"to a workspace chain; deleting workspace chain {ChainId}";
_logger.Debug(e, dbgMsg, workspace.Id);

if (workspace?.Id is Guid workspaceId && scope.Contains(workspaceId))
{
_store.DeleteChainId(workspaceId);
}

const string dbgMsg = "An exception occurred while appending a block";
_logger.Error(e, dbgMsg);
throw;
}
finally
{
foreach (var id in scope.Where(guid => guid != workspace?.Id))
{
_store.DeleteChainId(id);
}

_logger.Debug(
"Completed (chain ID: {ChainId}, tip: #{TipIndex} {TipHash}). " +
"at {MethodName}()",
workspace?.Id,
workspace?.Tip?.Index,
workspace?.Tip?.Hash,
nameof(AppendPreviousBlocks)
);
}

return workspace;
}

private Block FindBranchpoint(Block oldTip, List<Block> newBlocks)
private List<(Block, BlockCommit)> ExtractBlocksToAppend(Block branchpoint, Branch branch)
{
var newTip = newBlocks.Last();
while (oldTip.Index > newTip.Index &&
oldTip.PreviousHash is { } aPrev)
{
oldTip = BlockChain[aPrev];
}

while (newTip.Index > oldTip.Index &&
newTip.PreviousHash is { } bPrev)
{
try
{
newTip = newBlocks.Single(x => x.Hash.Equals(bPrev));
}
catch (ArgumentNullException)
{
newTip = BlockChain[bPrev];
}
catch (InvalidOperationException)
{
newTip = BlockChain[bPrev];
}
}

if (oldTip.Index != newTip.Index)
var trimmed = new List<(Block, BlockCommit)>();
bool matchFound = false;
foreach (var pair in branch.Blocks)
{
throw new ArgumentException(
"Some previous blocks of two blocks are orphan.",
nameof(oldTip)
);
}

while (oldTip.Index >= 0)
{
if (oldTip.Equals(newTip))
if (matchFound)
{
return oldTip;
trimmed.Add(pair);
}

if (oldTip.PreviousHash is { } aPrev &&
newTip.PreviousHash is { } bPrev)
else
{
oldTip = BlockChain[aPrev];
try
{
newTip = newBlocks.Single(x => x.Hash.Equals(bPrev));
}
catch (ArgumentNullException)
{
newTip = BlockChain[bPrev];
}

continue;
matchFound = branchpoint.Hash.Equals(pair.Item1.Hash);
}

break;
}

throw new ArgumentException(
"Two blocks do not have any ancestors in common.",
nameof(oldTip)
);
return trimmed;
}

private async Task<bool> ProcessBlockDemandAsync(
Expand Down
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