private IConnection BorrowLeastBusyConnection(IConnection[] connections)
{
var c = HostConnectionPool.MinInFlight(connections, ref _connectionIndex, _maxRequestsPerConnection, out var inFlight);
if (inFlight >= _maxRequestsPerConnection)
{
throw new BusyPoolException(_host.Address, _maxRequestsPerConnection, connections.Length);
}
ConsiderResizingPool(inFlight);
return(c);
}
/// <summary>
/// Gets existing connections snapshot.
/// If it's empty then it validates whether the pool is shutting down or the is down (in which case an exception is thrown).
/// </summary>
/// <exception cref="SocketException">Not connected.</exception>
private IConnection[] GetExistingConnections()
{
var connections = _connections.GetSnapshot();
if (connections.Length > 0)
{
return(connections);
}
if (IsClosing || !_host.IsUp)
{
// Should have not been considered as UP
throw HostConnectionPool.GetNotConnectedException();
}
return(connections);
}
/// <inheritdoc />
public async Task <IConnection> BorrowConnection()
{
var connections = await EnsureCreate().ConfigureAwait(false);
if (connections.Length == 0)
{
throw new DriverInternalError("No connection could be borrowed");
}
var c = HostConnectionPool.MinInFlight(connections, ref _connectionIndex, _maxRequestsPerConnection, out var inFlight);
if (inFlight >= _maxRequestsPerConnection)
{
throw new BusyPoolException(c.Address, _maxRequestsPerConnection, connections.Length);
}
ConsiderResizingPool(inFlight);
return(c);
}
/// <summary>
/// Ensures that the pool has at least contains 1 connection to the host.
/// </summary>
/// <returns>An Array of connections with 1 or more elements or throws an exception.</returns>
/// <exception cref="SocketException" />
/// <exception cref="AuthenticationException" />
/// <exception cref="UnsupportedProtocolVersionException" />
public async Task <IConnection[]> EnsureCreate()
{
var connections = _connections.GetSnapshot();
if (connections.Length > 0)
{
// Use snapshot to return as early as possible
return(connections);
}
if (IsClosing || !_host.IsUp)
{
// Should have not been considered as UP
throw HostConnectionPool.GetNotConnectedException();
}
if (!_canCreateForeground)
{
// Take a new snapshot
connections = _connections.GetSnapshot();
if (connections.Length > 0)
{
return(connections);
}
// It's not considered as connected
throw HostConnectionPool.GetNotConnectedException();
}
IConnection c;
try
{
// It should only await for the creation of the connection in few selected occasions:
// It's the first time accessing or it has been recently set as UP
// CreateOpenConnection() supports concurrent calls
c = await CreateOpenConnection(true).ConfigureAwait(false);
}
catch (Exception)
{
OnConnectionClosing();
throw;
}
StartCreatingConnection(null);
return(new[] { c });
}
/// <summary>
/// Opens one connection.
/// If a connection is being opened it yields the same task, preventing creation in parallel.
/// </summary>
/// <param name="satisfyWithAnOpenConnection">
/// Determines whether the Task should be marked as completed when there is a connection already opened.
/// </param>
/// <exception cref="SocketException">Throws a SocketException when the connection could not be established with the host</exception>
/// <exception cref="AuthenticationException" />
/// <exception cref="UnsupportedProtocolVersionException" />
private async Task <IConnection> CreateOpenConnection(bool satisfyWithAnOpenConnection)
{
var concurrentOpenTcs = Volatile.Read(ref _connectionOpenTcs);
// Try to exit early (cheap) as there could be another thread creating / finishing creating
if (concurrentOpenTcs != null)
{
// There is another thread opening a new connection
return(await concurrentOpenTcs.Task.ConfigureAwait(false));
}
var tcs = new TaskCompletionSource <IConnection>();
// Try to set the creation task source
concurrentOpenTcs = Interlocked.CompareExchange(ref _connectionOpenTcs, tcs, null);
if (concurrentOpenTcs != null)
{
// There is another thread opening a new connection
return(await concurrentOpenTcs.Task.ConfigureAwait(false));
}
if (IsClosing)
{
return(await FinishOpen(tcs, false, HostConnectionPool.GetNotConnectedException()).ConfigureAwait(false));
}
// Before creating, make sure that its still needed
// This method is the only one that adds new connections
// But we don't control the removal, use snapshot
var connectionsSnapshot = _connections.GetSnapshot();
if (connectionsSnapshot.Length >= _expectedConnectionLength)
{
if (connectionsSnapshot.Length == 0)
{
// Avoid race condition while removing
return(await FinishOpen(tcs, false, HostConnectionPool.GetNotConnectedException()).ConfigureAwait(false));
}
return(await FinishOpen(tcs, true, null, connectionsSnapshot[0]).ConfigureAwait(false));
}
if (satisfyWithAnOpenConnection && !_canCreateForeground)
{
// We only care about a single connection, if its already there, yield it
connectionsSnapshot = _connections.GetSnapshot();
if (connectionsSnapshot.Length == 0)
{
// When creating in foreground, it failed
return(await FinishOpen(tcs, false, HostConnectionPool.GetNotConnectedException()).ConfigureAwait(false));
}
return(await FinishOpen(tcs, false, null, connectionsSnapshot[0]).ConfigureAwait(false));
}
HostConnectionPool.Logger.Info("Creating a new connection to {0}", _host.Address);
IConnection c;
try
{
c = await DoCreateAndOpen().ConfigureAwait(false);
}
catch (Exception ex)
{
HostConnectionPool.Logger.Info("Connection to {0} could not be created: {1}", _host.Address, ex);
return(await FinishOpen(tcs, true, ex).ConfigureAwait(false));
}
if (IsClosing)
{
HostConnectionPool.Logger.Info("Connection to {0} opened successfully but pool #{1} was being closed",
_host.Address, GetHashCode());
c.Dispose();
return(await FinishOpen(tcs, false, HostConnectionPool.GetNotConnectedException()).ConfigureAwait(false));
}
var newLength = _connections.AddNew(c);
HostConnectionPool.Logger.Info("Connection to {0} opened successfully, pool #{1} length: {2}",
_host.Address, GetHashCode(), newLength);
if (IsClosing)
{
// We haven't use a CAS operation, so it's possible that the pool is being closed while adding a new
// connection, we should remove it.
HostConnectionPool.Logger.Info("Connection to {0} opened successfully and added to the pool #{1} but it was being closed",
_host.Address, GetHashCode());
_connections.Remove(c);
c.Dispose();
return(await FinishOpen(tcs, false, HostConnectionPool.GetNotConnectedException()).ConfigureAwait(false));
}
return(await FinishOpen(tcs, true, null, c).ConfigureAwait(false));
}