private async Task <(EndPointAddress endPoint, string securityToken)> AddClientCoreAsync(CancellationToken cancellation)
{
var now = _dateTimeProvider.GetCurrentTime();
var securityToken = Guid.NewGuid().ToString();
var leaseEnd = now + Timeout;
var securityTokenBytesCount = Encoding.UTF8.GetByteCount(securityToken);
using (ArrayPool <byte> .Shared.Rent(8 + 4 + securityTokenBytesCount, out var bytes))
{
var payloadLength = EncodePayload(bytes, securityToken.AsSpan(), leaseEnd);
var payload = bytes.AsMemory().Slice(start: 0, payloadLength);
EndPointAddress endPoint;
do
{
endPoint = AllocateEndPointAddress();
var path = GetPath(endPoint);
try
{
await _coordinationManager.CreateAsync(path, payload, cancellation : cancellation);
_logger?.LogDebug($"Assigning end-point '{endPoint.ToString()}' to recently connected client.");
break;
}
catch (DuplicateEntryException) // TODO: Add a TryCreateAsync method to the coordination service.
{
continue;
}
}while (cancellation.ThrowOrContinue());
return(endPoint, securityToken);
}
}
private static CoordinationEntryPath GetPrefixPath(ReadOnlyMemory <char> prefix, EndPointAddress endPoint, Session session, bool normalize = true)
{
if (normalize)
{
prefix = NormalizePrefix(prefix);
}
var uniqueEntryName = IdGenerator.GenerateId(endPoint.ToString(), session.ToString());
return(_rootPrefixesPath.GetChildPath(prefix, uniqueEntryName.AsMemory()));
}
private CoordinationEntryPath GetPath(EndPointAddress endPoint)
{
return(BasePath.GetChildPath(endPoint.ToString()));
}
private async Task <bool> ValidateClientCoreAsync(EndPointAddress endPoint,
string securityToken,
CancellationToken cancellation)
{
var now = _dateTimeProvider.GetCurrentTime();
var path = GetPath(endPoint);
do
{
var entry = await _coordinationManager.GetAsync(path, cancellation : cancellation);
if (entry == null)
{
_logger?.LogDebug($"Cannot update session for client with end-point '{endPoint.ToString()}'. Session is terminated.");
return(false);
}
var(comparandSecurityToken, leaseEnd) = DecodePayload(entry.Value.Span);
// We have to assume that the client is not connected anymore.
// This is a race condition, that has to be prevented.
if (now >= leaseEnd)
{
await _coordinationManager.DeleteAsync(entry.Path, cancellation : cancellation);
_logger?.LogDebug($"Session for client with end-point '{endPoint.ToString()}' is terminated. Removing entry.");
_logger?.LogDebug($"Cannot update session for client with end-point '{endPoint.ToString()}'. Session is terminated.");
return(false);
}
if (securityToken != comparandSecurityToken)
{
_logger?.LogDebug($"Cannot update session for client with end-point '{endPoint.ToString()}'. Session is terminated.");
return(false);
}
var newLeaseEnd = now + Timeout;
if (newLeaseEnd > leaseEnd)
{
leaseEnd = newLeaseEnd;
}
var securityTokenBytesCount = Encoding.UTF8.GetByteCount(securityToken);
using (ArrayPool <byte> .Shared.Rent(8 + 4 + securityTokenBytesCount, out var bytes))
{
var payloadLength = EncodePayload(bytes, securityToken.AsSpan(), leaseEnd);
var payload = bytes.AsMemory().Slice(start: 0, payloadLength);
endPoint = new EndPointAddress("client/" + Guid.NewGuid().ToString());
var version = await _coordinationManager.SetValueAsync(path, payload, version : entry.Version, cancellation : cancellation);
if (version == entry.Version)
{
_logger?.LogDebug($"Updated session for client with end-point '{endPoint.ToString()}'.");
return(true);
}
}
}while (true);
}