/// <summary>
/// This is an important operation for long lasting allocations.
/// For example the full sync tends to allocate the same peer for many minutes and we use this method to ensure that
/// a newly arriving better peer can replace a currently selected one.
/// Consider that there are some external changes (e.g. node stats values change based on the sync transfer rates)
/// which may not be controlled from inside here, hence we decide to monitor the potential upgrades in a loop.
/// </summary>
/// <exception cref="InvalidOperationException">Thrown if an irreplaceable allocation is being replaced by this method (internal implementation error).</exception>
private void UpgradeAllocations(string reason)
{
DropUselessPeers();
WakeUpPeerThatSleptEnough();
foreach ((SyncPeerAllocation allocation, _) in _replaceableAllocations)
{
lock (_isAllocatedChecks)
{
var unallocatedPeers = InitializedPeers.Where(p => p.CanBeAllocated(allocation.Contexts));
allocation.AllocateBestPeer(unallocatedPeers, _stats, _blockTree);
}
}
}
public async Task <SyncPeerAllocation> Allocate(IPeerAllocationStrategy peerAllocationStrategy, AllocationContexts allocationContexts = AllocationContexts.All, int timeoutMilliseconds = 0)
{
int tryCount = 1;
DateTime startTime = DateTime.UtcNow;
SyncPeerAllocation allocation = new SyncPeerAllocation(peerAllocationStrategy, allocationContexts);
while (true)
{
lock (_isAllocatedChecks)
{
allocation.AllocateBestPeer(InitializedPeers.Where(p => p.CanBeAllocated(allocationContexts)), _stats, _blockTree);
if (allocation.HasPeer)
{
if (peerAllocationStrategy.CanBeReplaced)
{
_replaceableAllocations.TryAdd(allocation, null);
}
return(allocation);
}
}
bool timeoutReached = timeoutMilliseconds == 0 ||
(DateTime.UtcNow - startTime).TotalMilliseconds > timeoutMilliseconds;
if (timeoutReached)
{
return(SyncPeerAllocation.FailedAllocation);
}
int waitTime = 10 * tryCount++;
if (!_signals.SafeWaitHandle.IsClosed)
{
await _signals.WaitOneAsync(waitTime, _refreshLoopCancellation.Token);
if (!_signals.SafeWaitHandle.IsClosed)
{
_signals.Reset(); // without this we have no delay
}
}
}
}
