/// <inheritdoc />
public LookaheadResult NextBlock(CancellationToken cancellationToken)
{
this.logger.LogTrace("()");
lock (this.downloadedCountsLock)
{
this.downloadedCounts.Add(this.DownloadedBlocksCount);
}
if (this.lookaheadLocation == null)
{
this.logger.LogTrace("Lookahead location is not initialized.");
// Calling twice is intentional here.
// lookaheadLocation is null only during initialization
// or when reorganisation happens. Calling this twice will
// make sure the initial work of the puller is away from
// the lower boundary.
this.AskBlocks();
this.AskBlocks();
}
LookaheadResult block = this.NextBlockCore(cancellationToken);
if (block != null)
{
if ((this.lookaheadLocation.Height - this.location.Height) <= this.ActualLookahead)
{
this.logger.LogTrace("Recalculating lookahead: Last request block height is {0}, last processed block height is {1}, {2} is {3}.", this.lookaheadLocation.Height, this.location.Height, nameof(this.ActualLookahead), this.ActualLookahead);
this.CalculateLookahead();
this.AskBlocks();
}
else
{
this.logger.LogTrace("Lookahead needs no adjustment.");
}
}
else
{
this.logger.LogTrace("Reorganization detected.");
}
this.logger.LogTrace("(-):'{0}'", block);
return(block);
}
/// <summary>
/// Waits for a next block to be available (downloaded).
/// </summary>
/// <param name="cancellationToken">Cancellation token to allow the caller to cancel waiting for the next block.</param>
/// <returns>Next block or null if a reorganization happened on the chain.</returns>
private LookaheadResult NextBlockCore(CancellationToken cancellationToken)
{
this.logger.LogTrace("()");
LookaheadResult res = new LookaheadResult();
while (res.Block == null)
{
cancellationToken.ThrowIfCancellationRequested();
this.logger.LogTrace("Requesting block at height {0}.", this.location.Height + 1);
ChainedBlock header = this.Chain.GetBlock(this.location.Height + 1);
DownloadedBlock block;
bool isDownloading = false;
bool isReady = false;
if (header != null)
{
this.CheckBlockStatus(header.HashBlock, out isDownloading, out isReady);
}
// If block has been downloaded and is ready to be consumed, then remove it from the list of downloaded blocks and consume it.
if (isReady && this.TryRemoveDownloadedBlock(header.HashBlock, out block))
{
this.logger.LogTrace("Consuming block '{0}'.", header.HashBlock);
if (header.Previous.HashBlock != this.location.HashBlock)
{
this.logger.LogTrace("Blockchain reorganization detected.");
break;
}
this.SetLocation(header);
lock (this.bufferLock)
{
this.currentBufferedSize -= block.Length;
this.currentBufferedCount--;
}
this.consumed.Set();
res.Block = block.Block;
}
else
{
// Otherwise we either have reorg, or we reached the best chain tip.
if (header == null)
{
if (!this.Chain.Contains(this.location.HashBlock))
{
this.logger.LogTrace("Blockchain reorganization detected.");
break;
}
this.logger.LogTrace("Hash of the next block is not known.");
}
else
{
this.logger.LogTrace("Block not available.");
// Or the block is still being downloaded or we need to ask for this block to be downloaded.
if (!isDownloading)
{
this.AskBlocks(new ChainedBlock[] { header });
}
this.OnStalling(header);
}
while (!cancellationToken.IsCancellationRequested)
{
var handles = new WaitHandle[] { this.pushed, this.consumed, cancellationToken.WaitHandle };
int handleIndex = WaitHandle.WaitAny(handles, WaitNextBlockRoundTimeMs);
if ((handleIndex != WaitHandle.WaitTimeout) && (handles[handleIndex] == this.consumed))
{
// Block has been consumed, check if we can ask for more blocks.
this.logger.LogTrace("Block has been previously consumed.");
this.ProcessQueue();
}
else
{
// Block has been pushed or wait timed out or cancellation token triggered.
// All cases are handled in external loop, so escape the inner loop.
break;
}
}
}
}
this.logger.LogTrace("(-):'{0}'", res);
return(res);
}