#255 Asynchronous Sending for RemoteSyslogAppender in log4net

src/log4net.Tests/Appender/Internal/UdpMock.cs

@@ -0,0 +1,60 @@
+#region Apache 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.Collections.Generic;
+using System.Net;
+using System.Threading.Tasks;
+using log4net.Appender.Internal;
+
+namespace log4net.Tests.Appender.Internal;
+
+/// <summary>
+/// Mock implementation of <see cref="IUdpConnection"/> for testing purposes.
+/// </summary>
+internal sealed class UdpMock : IUdpConnection
+{
+  /// <summary>
+  /// Passed to <see cref="SendAsync(byte[], int)"/>
+  /// </summary>
+  public List<(byte[] Datagram, int Bytes)> Sent { get; } = [];
+
+  /// <summary>
+  /// Was <see cref="Dispose"/> called
+  /// </summary>
+  internal bool WasDisposed { get; private set; }
+
+  /// <summary>
+  /// Parameters passed to <see cref="Connect(int, IPAddress, int)"/>
+  /// </summary>
+  internal (int LocalPort, IPAddress Host, int RemotePort)? ConnectedTo { get; private set; }
+
+  /// <inheritdoc/>
+  public void Connect(int localPort, IPAddress host, int remotePort) 
+    => ConnectedTo = (localPort, host, remotePort);
+
+  /// <inheritdoc/>
+  public void Dispose() => WasDisposed = true;
+
+  /// <inheritdoc/>
+  public Task<int> SendAsync(byte[] datagram, int bytes)
+  {
+    Sent.Add((datagram, bytes));
+    return Task.FromResult(bytes);
+  }
+}

src/log4net.Tests/Appender/RemoteSyslogAppenderTest.cs

@@ -0,0 +1,75 @@
+#region Apache 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.Text;
+using log4net.Appender;
+using log4net.Appender.Internal;
+using log4net.Core;
+using log4net.Layout;
+using log4net.Tests.Appender.Internal;
+using NUnit.Framework;
+
+namespace log4net.Tests.Appender;
+
+/// <summary>
+/// Tests for <see cref="RemoteSyslogAppender"/>
+/// </summary>
+[TestFixture]
+public sealed class RemoteSyslogAppenderTest
+{
+  private sealed class RemoteAppender : RemoteSyslogAppender
+  {
+    /// <summary>
+    /// Mock
+    /// </summary>
+    internal UdpMock Mock { get; } = new();
+
+    /// <inheritdoc/>
+    protected override IUdpConnection CreateUdpConnection() => Mock;
+  }
+
+  /// <summary>
+  /// Simple Test for the <see cref="RemoteSyslogAppenderTest"/>
+  /// </summary>
+  /// <remarks>
+  /// https://github.com/apache/logging-log4net/issues/255
+  /// </remarks>
+  [Test]
+  public void RemoteSyslogTest()
+  {
+    System.Net.IPAddress ipAddress = new([127, 0, 0, 1]);
+    RemoteAppender appender = new() { RemoteAddress = ipAddress, Layout = new PatternLayout("%-5level - %message%newline") };
+    appender.ActivateOptions();
+    LoggingEvent loggingEvent = new(new()
+    {
+      Level = Level.Info,
+      Message = "Test message",
+      LoggerName = "TestLogger",
+      Domain = "TestDomain",
+    });
+    appender.DoAppend(loggingEvent);
+    appender.Close();
+    Assert.That(appender.Mock.ConnectedTo, Is.EqualTo((0, ipAddress, 514)));
+    Assert.That(appender.Mock.Sent, Has.Count.EqualTo(1));
+    Assert.That(appender.Mock.WasDisposed, Is.True);
+    Assert.That(appender.Mock.Sent, Has.Count.EqualTo(1));
+    const string expectedData = @"<14>TestDomain: INFO  - Test message";
+    Assert.That(Encoding.ASCII.GetString(appender.Mock.Sent[0].Datagram), Is.EqualTo(expectedData));
+  }
+}

src/log4net.Tests/Appender/TelnetAppenderTest.cs

@@ -1,4 +1,4 @@
-#region Apache License
+#region Apache License
 //
 // Licensed to the Apache Software Foundation (ASF) under one or more 
 // contributor license agreements. See the NOTICE file distributed with
@@ -37,7 +37,7 @@ namespace log4net.Tests.Appender;
 public sealed class TelnetAppenderTest
 {
   /// <summary>
-  /// Simple Test für the <see cref="TelnetAppender"/>
+  /// Simple Test for the <see cref="TelnetAppender"/>
   /// </summary>
   /// <remarks>
   /// https://github.com/apache/logging-log4net/issues/194

src/log4net/Appender/AppenderSkeleton.cs

@@ -353,7 +353,7 @@ public void DoAppend(LoggingEvent[] loggingEvents)
       {
         _recursiveGuard = true;
 
-        var filteredEvents = new List<LoggingEvent>(loggingEvents.Length);
+        List<LoggingEvent> filteredEvents = new(loggingEvents.Length);
 
         foreach (LoggingEvent loggingEvent in loggingEvents)
         {
@@ -628,7 +628,7 @@ protected string RenderLoggingEvent(LoggingEvent loggingEvent)
     lock (LockObj)
     {
       // Create the render writer on first use
-      _renderWriter ??= new ReusableStringWriter(System.Globalization.CultureInfo.InvariantCulture);
+      _renderWriter ??= new(System.Globalization.CultureInfo.InvariantCulture);
 
       // Reset the writer so we can reuse it
       _renderWriter.Reset(RenderBufferMaxCapacity, RenderBufferSize);

src/log4net/Appender/Internal/IUdpConnection.cs

@@ -0,0 +1,51 @@
+#region Apache 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.ComponentModel;
+using System.Net;
+using System.Threading.Tasks;
+
+namespace log4net.Appender.Internal;
+
+/// <summary>
+/// Interface for UDP connection management.
+/// Only public for unit testing purposes.
+/// Do not use outside of log4net.
+/// Signatures may change without notice.
+/// </summary>
+[EditorBrowsable(EditorBrowsableState.Never)]
+public interface IUdpConnection : IDisposable
+{
+  /// <summary>
+  /// Establishes a default remote host using the specified host name and port number.
+  /// </summary>
+  /// <param name="localPort">The local port number</param>
+  /// <param name="host">The remote host to which you intend send data.</param>
+  /// <param name="remotePort">The port number on the remote host to which you intend to send data.</param>
+  void Connect(int localPort, IPAddress host, int remotePort);
+
+  /// <summary>
+  /// Sends a UDP datagram asynchronously to a remote host.
+  /// </summary>
+  /// <param name="datagram">An array of type System.Byte that specifies the UDP datagram that you intend to send represented as an array of bytes.</param>
+  /// <param name="bytes">The number of bytes in the datagram.</param>
+  /// <returns>Task for Completion</returns>
+  Task<int> SendAsync(byte[] datagram, int bytes);
+}

src/log4net/Appender/Internal/UdpConnection.cs

@@ -0,0 +1,58 @@
+#region Apache 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.Net;
+using System.Net.Sockets;
+using System.Threading.Tasks;
+using log4net.Util;
+
+namespace log4net.Appender.Internal;
+
+/// <summary>
+/// Wrapper for <see cref="UdpClient"/> to manage UDP connections.
+/// </summary>
+internal sealed class UdpConnection : IUdpConnection
+{
+  private UdpClient? _client;
+
+  private UdpClient Client 
+    => _client.EnsureNotNull(errorMessage: "Client is not initialized. Call Connect first.");
+
+  /// <inheritdoc/>
+  public void Connect(int localPort, IPAddress remoteAddress, int remotePort)
+  {
+    _client = CreateClient(localPort, remoteAddress);
+    Client.Connect(remoteAddress, remotePort);
+  }
+
+  /// <inheritdoc/>
+  public Task<int> SendAsync(byte[] datagram, int bytes) => Client.SendAsync(datagram, bytes);
+
+  /// <inheritdoc/>
+  public void Dispose() => _client?.Dispose();
+
+  /// <summary>
+  /// Creates a new <see cref="UdpClient"/> instance configured with the specified local port and remote address.
+  /// </summary>
+  /// <returns>A <see cref="UdpClient"/> instance configured with the specified parameters.</returns>
+  internal static UdpClient CreateClient(int localPort, System.Net.IPAddress remoteAddress)
+    => localPort == 0
+      ? new (remoteAddress.AddressFamily)
+      : new (localPort, remoteAddress.AddressFamily);
+}