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Connection.cs
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Connection.cs
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#region License
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
#endregion
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Gremlin.Net.Driver.Messages;
using Gremlin.Net.Process;
namespace Gremlin.Net.Driver
{
internal interface IResponseHandlerForSingleRequestMessage
{
void HandleReceived(ResponseMessage<List<object>> received);
void Finalize(Dictionary<string, object> statusAttributes);
void HandleFailure(Exception objException);
void Cancel();
}
internal class Connection : IConnection
{
private readonly IMessageSerializer _messageSerializer;
private readonly Uri _uri;
private readonly IWebSocketConnection _webSocketConnection;
private readonly string _username;
private readonly string _password;
private readonly string _sessionId;
private readonly bool _sessionEnabled;
private readonly ConcurrentQueue<(RequestMessage msg, CancellationToken cancellationToken)> _writeQueue =
new ConcurrentQueue<(RequestMessage, CancellationToken)>();
private readonly ConcurrentDictionary<Guid, IResponseHandlerForSingleRequestMessage> _callbackByRequestId =
new ConcurrentDictionary<Guid, IResponseHandlerForSingleRequestMessage>();
private readonly List<CancellationTokenRegistration> _cancellationTokenRegistrations =
new List<CancellationTokenRegistration>();
private int _connectionState = 0;
private int _writeInProgress = 0;
private const int Closed = 1;
public Connection(IWebSocketConnection webSocketConnection, Uri uri, string username, string password,
IMessageSerializer messageSerializer, string sessionId)
{
_uri = uri;
_username = username;
_password = password;
_sessionId = sessionId;
if (!string.IsNullOrEmpty(sessionId))
{
_sessionEnabled = true;
}
_messageSerializer = messageSerializer;
_webSocketConnection = webSocketConnection;
}
public async Task ConnectAsync(CancellationToken cancellationToken)
{
await _webSocketConnection.ConnectAsync(_uri, cancellationToken).ConfigureAwait(false);
BeginReceiving();
}
public int NrRequestsInFlight => _callbackByRequestId.Count;
public bool IsOpen => _webSocketConnection.IsOpen && Volatile.Read(ref _connectionState) != Closed;
public Task<ResultSet<T>> SubmitAsync<T>(RequestMessage requestMessage, CancellationToken cancellationToken)
{
var receiver = new ResponseHandlerForSingleRequestMessage<T>();
_callbackByRequestId.GetOrAdd(requestMessage.RequestId, receiver);
_cancellationTokenRegistrations.Add(cancellationToken.Register(() =>
{
if (_callbackByRequestId.TryRemove(requestMessage.RequestId, out var responseHandler))
{
responseHandler.Cancel();
}
}));
_writeQueue.Enqueue((requestMessage, cancellationToken));
BeginSendingMessages();
return receiver.Result;
}
private void BeginReceiving()
{
var state = Volatile.Read(ref _connectionState);
if (state == Closed) return;
ReceiveMessagesAsync().Forget();
}
private async Task ReceiveMessagesAsync()
{
while (true)
{
try
{
var received = await _webSocketConnection.ReceiveMessageAsync().ConfigureAwait(false);
await HandleReceivedAsync(received).ConfigureAwait(false);
}
catch (Exception e)
{
await CloseConnectionBecauseOfFailureAsync(e).ConfigureAwait(false);
break;
}
}
}
private async Task HandleReceivedAsync(byte[] received)
{
var receivedMsg = await _messageSerializer.DeserializeMessageAsync(received).ConfigureAwait(false);
if (receivedMsg == null)
{
ThrowMessageDeserializedNull();
}
try
{
HandleReceivedMessage(receivedMsg);
}
catch (Exception e)
{
if (receivedMsg.RequestId != null &&
_callbackByRequestId.TryRemove(receivedMsg.RequestId.Value, out var responseHandler))
{
responseHandler?.HandleFailure(e);
}
}
}
private static void ThrowMessageDeserializedNull() =>
throw new InvalidOperationException("Received data deserialized into null object message. Cannot operate on it.");
private void HandleReceivedMessage(ResponseMessage<List<object>> receivedMsg)
{
var status = receivedMsg.Status;
status.ThrowIfStatusIndicatesError();
if (status.Code == ResponseStatusCode.Authenticate)
{
Authenticate();
return;
}
if (receivedMsg.RequestId == null) return;
_callbackByRequestId.TryGetValue(receivedMsg.RequestId.Value, out var responseHandler);
if (status.Code != ResponseStatusCode.NoContent)
{
responseHandler?.HandleReceived(receivedMsg);
}
if (status.Code == ResponseStatusCode.Success || status.Code == ResponseStatusCode.NoContent)
{
responseHandler?.Finalize(status.Attributes);
_callbackByRequestId.TryRemove(receivedMsg.RequestId.Value, out _);
}
}
private void Authenticate()
{
if (string.IsNullOrEmpty(_username) || string.IsNullOrEmpty(_password))
throw new InvalidOperationException(
$"The Gremlin Server requires authentication, but no credentials are specified - username: {_username}, password: {_password}.");
var message = RequestMessage.Build(Tokens.OpsAuthentication).Processor(Tokens.ProcessorTraversal)
.AddArgument(Tokens.ArgsSasl, SaslArgument()).Create();
_writeQueue.Enqueue((message, CancellationToken.None));
BeginSendingMessages();
}
private string SaslArgument()
{
var auth = $"\0{_username}\0{_password}";
var authBytes = Encoding.UTF8.GetBytes(auth);
return Convert.ToBase64String(authBytes);
}
private void BeginSendingMessages()
{
if (Interlocked.CompareExchange(ref _writeInProgress, 1, 0) != 0)
return;
SendMessagesFromQueueAsync().Forget();
}
private async Task SendMessagesFromQueueAsync()
{
while (_writeQueue.TryDequeue(out var msg))
{
try
{
await SendMessageAsync(msg.msg, msg.cancellationToken).ConfigureAwait(false);
}
catch (OperationCanceledException e) when (msg.cancellationToken == e.CancellationToken)
{
// Send was cancelled for this message -> silently catch as we want to continue sending from this
// connection. The task responsible for submitting this message will be cancelled by the
// `ResponseHandlerForSingleRequestMessage`.
}
catch (Exception e)
{
await CloseConnectionBecauseOfFailureAsync(e).ConfigureAwait(false);
break;
}
}
Interlocked.CompareExchange(ref _writeInProgress, 0, 1);
// Since the loop ended and the write in progress was set to 0
// a new item could have been added, write queue can contain items at this time
if (!_writeQueue.IsEmpty && Interlocked.CompareExchange(ref _writeInProgress, 1, 0) == 0)
{
await SendMessagesFromQueueAsync().ConfigureAwait(false);
}
}
private async Task CloseConnectionBecauseOfFailureAsync(Exception exception)
{
EmptyWriteQueue();
await CloseAsync().ConfigureAwait(false);
NotifyAboutConnectionFailure(exception);
}
private void EmptyWriteQueue()
{
while (_writeQueue.TryDequeue(out _))
{
}
}
private void NotifyAboutConnectionFailure(Exception exception)
{
foreach (var cb in _callbackByRequestId.Values)
{
cb.HandleFailure(exception);
}
_callbackByRequestId.Clear();
}
private async Task SendMessageAsync(RequestMessage message, CancellationToken cancellationToken)
{
if (_sessionEnabled)
{
message = RebuildSessionMessage(message);
}
var serializedMsg = await _messageSerializer.SerializeMessageAsync(message, cancellationToken)
.ConfigureAwait(false);
#if NET6_0_OR_GREATER
if (message.Processor == Tokens.OpsAuthentication)
{
// Don't compress a message that contains credentials to prevent attacks like CRIME or BREACH
await _webSocketConnection.SendMessageUncompressedAsync(serializedMsg, cancellationToken).ConfigureAwait(false);
return;
}
#endif
await _webSocketConnection.SendMessageAsync(serializedMsg, cancellationToken).ConfigureAwait(false);
}
private RequestMessage RebuildSessionMessage(RequestMessage message)
{
if (message.Processor == Tokens.OpsAuthentication)
{
return message;
}
var msgBuilder = RequestMessage.Build(message.Operation)
.OverrideRequestId(message.RequestId).Processor(Tokens.ProcessorSession);
foreach(var kv in message.Arguments)
{
msgBuilder.AddArgument(kv.Key, kv.Value);
}
msgBuilder.AddArgument(Tokens.ArgsSession, _sessionId);
return msgBuilder.Create();
}
public async Task CloseAsync()
{
Interlocked.Exchange(ref _connectionState, Closed);
if (_sessionEnabled)
{
await CloseSession().ConfigureAwait(false);
}
await _webSocketConnection.CloseAsync().ConfigureAwait(false);
}
private async Task CloseSession()
{
// build a request to close this session
var msg = RequestMessage.Build(Tokens.OpsClose).Processor(Tokens.ProcessorSession).Create();
await SendMessageAsync(msg, CancellationToken.None).ConfigureAwait(false);
}
#region IDisposable Support
private bool _disposed;
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (!_disposed)
{
if (disposing)
{
_webSocketConnection?.Dispose();
foreach (var registration in _cancellationTokenRegistrations)
{
registration.Dispose();
}
}
_disposed = true;
}
}
#endregion
}
}