/// <summary>
/// Schedules downloading of one or more blocks that the node is missing from one or more peer nodes.
/// <para>
/// Node's quality score is being considered as a weight during the random distribution
/// of the download tasks among the nodes.
/// </para>
/// <para>
/// Nodes are only asked for blocks that they should have (according to our information
/// about how long their chains are).
/// </para>
/// </summary>
/// <param name="vectors">List of information about blocks to download mapped by their height. Must not be empty.</param>
/// <param name="minHeight">Minimum height of the chain that the target nodes has to have in order to be asked for one or more of the block to be downloaded from them.</param>
private void DistributeDownload(Dictionary <int, InventoryVector> vectors, int minHeight)
{
this.logger.LogTrace("({0}.{1}:{2},{3}:{4})", nameof(vectors), nameof(vectors.Count), vectors.Count, nameof(minHeight), minHeight);
// Count number of tasks assigned to each peer.
BlockPullerBehavior[] nodes = this.GetNodeBehaviors();
Dictionary <BlockPullerBehavior, int> assignedTasksCount = new Dictionary <BlockPullerBehavior, int>();
lock (this.lockObject)
{
foreach (BlockPullerBehavior behavior in nodes)
{
int taskCount = 0;
Dictionary <uint256, DownloadAssignment> peerPendingDownloads;
if (this.peersPendingDownloads.TryGetValue(behavior, out peerPendingDownloads))
{
taskCount = peerPendingDownloads.Keys.Count;
}
assignedTasksCount.Add(behavior, taskCount);
}
}
// Prefilter available peers so that we only work with peers that can be assigned any work.
// If there is a peer whose chain is so short that it can't provide any blocks we want, it is ignored.
List <PullerDownloadAssignments.PeerInformation> peerInformation = new List <PullerDownloadAssignments.PeerInformation>();
foreach (BlockPullerBehavior behavior in nodes)
{
int?peerHeight = behavior.ChainHeadersBehavior?.PendingTip?.Height;
if (peerHeight >= minHeight)
{
PullerDownloadAssignments.PeerInformation peerInfo = new PullerDownloadAssignments.PeerInformation
{
QualityScore = behavior.QualityScore,
PeerId = behavior,
ChainHeight = peerHeight.Value,
TasksAssignedCount = assignedTasksCount[behavior]
};
peerInformation.Add(peerInfo);
this.logger.LogTrace("Peer '{0:x}' available: quality {1}, height {2}.", peerInfo.PeerId.GetHashCode(), peerInfo.QualityScore, peerInfo.ChainHeight);
}
else
{
this.logger.LogTrace("Peer '{0:x}' filtered out: height {1}.", behavior.GetHashCode(), peerHeight);
}
}
// There are no available peers with long enough chains.
if (peerInformation.Count == 0)
{
lock (this.lockObject)
{
foreach (InventoryVector vector in vectors.Values)
{
this.pendingInventoryVectors.Enqueue(vector.Hash);
}
}
this.logger.LogTrace("(-)[NO_PEERS_LEFT]");
return;
}
List <int> requestedBlockHeights = vectors.Keys.ToList();
Dictionary <PullerDownloadAssignments.PeerInformation, List <int> > blocksAssignedToPeers = PullerDownloadAssignments.AssignBlocksToPeers(requestedBlockHeights, peerInformation);
// Go through the assignments and start download tasks.
foreach (KeyValuePair <PullerDownloadAssignments.PeerInformation, List <int> > kvp in blocksAssignedToPeers)
{
PullerDownloadAssignments.PeerInformation peer = kvp.Key;
List <int> blockHeightsToDownload = kvp.Value;
GetDataPayload getDataPayload = new GetDataPayload();
BlockPullerBehavior peerBehavior = (BlockPullerBehavior)peer.PeerId;
// Create GetDataPayload from the list of block heights this peer has been assigned.
bool peerDisconnected = false;
foreach (int blockHeight in blockHeightsToDownload)
{
InventoryVector inventoryVector = vectors[blockHeight];
if (this.AssignDownloadTaskToPeer(peerBehavior, inventoryVector.Hash, out peerDisconnected))
{
this.logger.LogTrace("Block '{0}/{1}' assigned to peer '{2:x}'", inventoryVector.Hash, blockHeight, peerBehavior.GetHashCode());
getDataPayload.Inventory.Add(inventoryVector);
}
else if (peerDisconnected)
{
// The peer was disconnected recently, we need to make sure that the blocks assigned to it go back to the pending list.
// This is done below.
this.logger.LogTrace("Peer '{0:x} has been disconnected.'", peerBehavior.GetHashCode());
break;
}
// else This block has been assigned to someone else already, no action required.
}
if (!peerDisconnected)
{
// If this node was assigned at least one download task, start the task.
if (getDataPayload.Inventory.Count > 0)
{
peerDisconnected = !peerBehavior.StartDownloadAsync(getDataPayload).GetAwaiter().GetResult();
}
}
if (peerDisconnected)
{
// Return blocks that were supposed to be assigned to the disconnected peer back to the pending list.
lock (this.lockObject)
{
foreach (int blockHeight in blockHeightsToDownload)
{
InventoryVector inventoryVector = vectors[blockHeight];
this.pendingInventoryVectors.Enqueue(inventoryVector.Hash);
}
}
}
}
this.logger.LogTrace("(-)");
}
