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Merge pull request #54 from aspriddell/io-lock
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add read-write lock to replace loops
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@aspriddell
aspriddell authored Dec 23, 2020
2 parents c06ccae + 451680c commit ee3e88a
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Showing 2 changed files with 46 additions and 51 deletions.
94 changes: 44 additions & 50 deletions DragonFruit.Common.Data/ApiClient.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
using DragonFruit.Common.Data.Exceptions;
Expand Down Expand Up @@ -45,11 +46,15 @@ public ApiClient(ISerializer serializer)
Serializer = serializer;
Headers = new HeaderCollection(this);

_lock = new ReaderWriterLockSlim(LockRecursionPolicy.NoRecursion);

RequestClientReset(true);
}

~ApiClient()
{
_lock?.Dispose();

Client?.Dispose();
}

Expand Down Expand Up @@ -105,22 +110,18 @@ public Func<HttpMessageHandler> Handler
public ISerializer Serializer { get; set; }

/// <summary>
/// <see cref="HttpClient"/> used by these requests. This is used by the library and as such, should **not** be disposed in any way
/// <see cref="HttpClient"/> used by these requests.
/// This is used by the library and as such, should **not** be disposed in any way
/// </summary>
protected HttpClient Client { get; private set; }

/// <summary>
/// Time, in milliseconds to wait to modify a <see cref="HttpClient"/> before failing the request
/// </summary>
protected virtual int AdjustmentTimeout => 200;

#endregion

#region Private Vars

private readonly ReaderWriterLockSlim _lock;
private long _clientAdjustmentRequestSignal;
private Func<HttpMessageHandler> _handler;
private int _clientAdjustmentSignal;
private long _clientAdjustmentRequestSignal, _currentRequests;

#endregion

Expand All @@ -134,50 +135,41 @@ protected HttpClient GetClient()
// return current client if there are no changes
var resetLevel = Interlocked.Read(ref _clientAdjustmentRequestSignal);

if (resetLevel == 0)
{
return Client;
}

// if we're waiting, then don't cause a crash from getting the wrong client - just wait.
while (Interlocked.CompareExchange(ref _clientAdjustmentSignal, 1, 0) == 1)
if (resetLevel > 0)
{
Timeout();
}
// block all reads and let all current requests finish
_lock.EnterWriteLock();

try
{
// wait for all ongoing requests to end
while (_currentRequests > 0)
try
{
Timeout();
}
// only reset the client if the handler has changed (signal = 2)
var resetClient = resetLevel == 2;

// only reset the client if the handler has changed (signal = 2)
var resetClient = resetLevel == 2;
if (resetClient)
{
var handler = CreateHandler();

if (resetClient)
{
var handler = CreateHandler();

Client?.Dispose();
Client = handler != null ? new HttpClient(handler, true) : new HttpClient();
}
Client?.Dispose();
Client = handler != null ? new HttpClient(handler, true) : new HttpClient();
}

// apply new headers
Headers.ApplyTo(Client);
// apply new headers
Headers.ApplyTo(Client);

// allow the conumer to change the client
SetupClient(Client, resetClient);
// allow the consumer to change the client
SetupClient(Client, resetClient);

// reset the state
Interlocked.Exchange(ref _clientAdjustmentRequestSignal, 0);
return Client;
}
finally
{
Interlocked.Exchange(ref _clientAdjustmentSignal, 0);
// reset the state
Interlocked.Exchange(ref _clientAdjustmentRequestSignal, 0);
}
finally
{
_lock.ExitWriteLock();
}
}

_lock.EnterReadLock();
return Client;
}

#endregion
Expand Down Expand Up @@ -299,9 +291,7 @@ HttpResponseMessage CopyProcess(HttpResponseMessage response)
/// <param name="disposeResponse">Whether to dispose of the <see cref="HttpResponseMessage"/> produced after <see cref="processResult"/> has been invoked.</param>
protected T InternalPerform<T>(HttpRequestMessage request, Func<HttpResponseMessage, T> processResult, bool disposeResponse, CancellationToken token = default)
{
//get client and request (disposables)
var client = GetClient();
Interlocked.Increment(ref _currentRequests);

// post-modification
SetupRequest(request);
Expand All @@ -318,15 +308,14 @@ protected T InternalPerform<T>(HttpRequestMessage request, Func<HttpResponseMess
response = client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, token).Result;
#endif

//all possible exceptions from client.SendAsync() will be released here
// all possible exceptions from client.SendAsync() will be released here
return processResult.Invoke(response);
}
finally
{
//un-bump reqs
Interlocked.Decrement(ref _currentRequests);
RequestFinished();

//dispose
// dispose
if (disposeResponse)
{
response?.Dispose();
Expand Down Expand Up @@ -366,6 +355,10 @@ protected virtual void ValidateRequest(ApiRequest request)
}
}

/// <summary>
/// Requests the client is reset on the next request
/// </summary>
/// <param name="fullReset">Whether to reset the <see cref="HttpClient"/> as well as the headers</param>
public void RequestClientReset(bool fullReset)
{
if (fullReset)
Expand All @@ -378,6 +371,7 @@ public void RequestClientReset(bool fullReset)
}
}

private void Timeout() => Thread.Sleep(AdjustmentTimeout / 2);
[MethodImpl(MethodImplOptions.AggressiveInlining)]
protected void RequestFinished() => _lock.ExitReadLock();
}
}
3 changes: 2 additions & 1 deletion DragonFruit.Common.Data/Headers/HeaderCollection.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,11 +9,12 @@ namespace DragonFruit.Common.Data.Headers
{
public class HeaderCollection
{
private readonly ConcurrentDictionary<string, string> _values = new ConcurrentDictionary<string, string>();
private readonly ConcurrentDictionary<string, string> _values;
private readonly ApiClient _client;

public HeaderCollection(ApiClient client)
{
_values = new ConcurrentDictionary<string, string>();
_client = client;
}

Expand Down

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