Self-Diagnostics: include datetimestamp in filename

BASE/Test/Microsoft.ApplicationInsights.Test/Microsoft.ApplicationInsights.Tests/Extensibility/Implementation/Tracing/SelfDiagnostics/MemoryMappedFileHandlerTest.cs

@@ -15,15 +15,16 @@ public class MemoryMappedFileHandlerTest
         [TestMethod]
         public void MemoryMappedFileHandler_Success()
         {
-            var fileName = Path.GetFileName(Process.GetCurrentProcess().MainModule.FileName) + "."
-                    + Process.GetCurrentProcess().Id + ".log";
+            string filePath;
             var fileSize = 1024;
             using (var handler = new MemoryMappedFileHandler())
             {
                 handler.CreateLogFile(".", fileSize);
+
+                filePath = handler.CurrentFilePath;
             }
 
-            var actualBytes = ReadFile(fileName, MessageOnNewFile.Length);
+            var actualBytes = ReadFile(filePath, MessageOnNewFile.Length);
 
             CollectionAssert.AreEqual(MessageOnNewFile, actualBytes);
         }
@@ -36,27 +37,29 @@ public void MemoryMappedFileHandler_Circular_Success()
             var messageToOverflow = Encoding.UTF8.GetBytes("1234567");
             var expectedBytesAtEnd = Encoding.UTF8.GetBytes("1234");
             var expectedBytesAtStart = Encoding.UTF8.GetBytes("567cessfully opened file.\n");
+            string filePath;
+
             using (var handler = new MemoryMappedFileHandler())
             {
                 handler.CreateLogFile(".", fileSize);
 
                 handler.Write(buffer, fileSize - MessageOnNewFile.Length - expectedBytesAtEnd.Length);
 
                 handler.Write(messageToOverflow, messageToOverflow.Length);
+
+                filePath = handler.CurrentFilePath;
             }
 
-            var fileName = Path.GetFileName(Process.GetCurrentProcess().MainModule.FileName) + "."
-                    + Process.GetCurrentProcess().Id + ".log";
-            var actualBytes = ReadFile(fileName, buffer.Length);
+            var actualBytes = ReadFile(filePath, buffer.Length);
 
             CollectionAssert.AreEqual(expectedBytesAtStart, SubArray(actualBytes, 0, expectedBytesAtStart.Length));
             CollectionAssert.AreEqual(expectedBytesAtEnd, SubArray(actualBytes, actualBytes.Length - expectedBytesAtEnd.Length, expectedBytesAtEnd.Length));
         }
 
-        private static byte[] ReadFile(string fileName, int byteCount)
+        private static byte[] ReadFile(string filePath, int byteCount)
         {
             byte[] actualBytes = new byte[byteCount];
-            using (var file = File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
+            using (var file = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
             {
                 file.Read(actualBytes, 0, byteCount);
             }

BASE/Test/Microsoft.ApplicationInsights.Test/Microsoft.ApplicationInsights.Tests/Extensibility/Implementation/Tracing/SelfDiagnostics/SelfDiagnosticsConfigRefresherTest.cs

@@ -27,8 +27,10 @@ public void SelfDiagnosticsConfigRefresher_OmitAsConfigured()
                     // Emitting event of EventLevel.Warning
                     CoreEventSource.Log.OperationIsNullWarning();
 
+                    var filePath = configRefresher.CurrentFilePath;
+
                     int bufferSize = 512;
-                    byte[] actualBytes = ReadFile(bufferSize);
+                    byte[] actualBytes = ReadFile(filePath, bufferSize);
                     string logText = Encoding.UTF8.GetString(actualBytes);
                     Assert.IsTrue(logText.StartsWith(MessageOnNewFileString));
 
@@ -52,8 +54,10 @@ public void SelfDiagnosticsConfigRefresher_CaptureAsConfigured()
                     // Emitting event of EventLevel.Error
                     CoreEventSource.Log.InvalidOperationToStopError();
 
+                    var filePath = configRefresher.CurrentFilePath;
+
                     int bufferSize = 512;
-                    byte[] actualBytes = ReadFile(bufferSize);
+                    byte[] actualBytes = ReadFile(filePath, bufferSize);
                     string logText = Encoding.UTF8.GetString(actualBytes);
                     Assert.IsTrue(logText.StartsWith(MessageOnNewFileString));
 
@@ -77,12 +81,9 @@ private static string ParseLogMessage(string logLine)
             return logLine.Substring(timestampPrefixLength);
         }
 
-        private static byte[] ReadFile(int byteCount)
+        private static byte[] ReadFile(string filePath, int byteCount)
         {
-            var outputFileName = Path.GetFileName(Process.GetCurrentProcess().MainModule.FileName) + "."
-                    + Process.GetCurrentProcess().Id + ".log";
-            var outputFilePath = Path.Combine(".", outputFileName);
-            using (var file = File.Open(outputFilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
+            using (var file = File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
             {
                 byte[] actualBytes = new byte[byteCount];
                 file.Read(actualBytes, 0, byteCount);

BASE/src/Microsoft.ApplicationInsights/Extensibility/Implementation/Tracing/SelfDiagnostics/MemoryMappedFileHandler.cs

@@ -2,6 +2,7 @@ namespace Microsoft.ApplicationInsights.Extensibility.Implementation.Tracing.Sel
 {
     using System;
     using System.Diagnostics;
+    using System.Globalization;
     using System.IO;
     using System.IO.MemoryMappedFiles;
     using System.Text;
@@ -38,6 +39,8 @@ internal class MemoryMappedFileHandler : IDisposable
 
         public int LogFileSize { get => this.logFileSize; private set => this.logFileSize = value; }
 
+        public string CurrentFilePath => this.underlyingFileStreamForMemoryMappedFile?.Name;
+
         /// <summary>
         /// Create a log file. If the file already exists, it will be overwritten.
         /// </summary>
@@ -48,8 +51,7 @@ public void CreateLogFile(string logDirectory, int fileSize)
             try
             {
                 Directory.CreateDirectory(logDirectory);
-                var fileName = Path.GetFileName(Process.GetCurrentProcess().MainModule.FileName) + "."
-                    + Process.GetCurrentProcess().Id + ".log";
+                var fileName = GenerateFileName();
                 var filePath = Path.Combine(logDirectory, fileName);
 
                 // Because the API [MemoryMappedFile.CreateFromFile][1](the string version) behaves differently on
@@ -162,6 +164,17 @@ public virtual void Write(byte[] buffer, int byteCount)
             }
         }
 
+        private static string GenerateFileName()
+        {
+            var dateTimeStamp = DateTime.UtcNow.ToString("yyyyMMdd-HHmmss", CultureInfo.InvariantCulture);
+
+            var currentProcess = Process.GetCurrentProcess();
+            var processFileName = Path.GetFileName(currentProcess.MainModule.FileName);
+            var processId = currentProcess.Id;
+
+            return $"{dateTimeStamp}.{processFileName}.{processId}.log";
+        }
+
         /// <summary>
         /// Try to get the log stream which is seeked to the position where the next line of log should be written.
         /// </summary>

BASE/src/Microsoft.ApplicationInsights/Extensibility/Implementation/Tracing/SelfDiagnostics/SelfDiagnosticsConfigRefresher.cs

@@ -37,6 +37,8 @@ public SelfDiagnosticsConfigRefresher()
             this.worker = Task.Run(() => this.Worker(this.cancellationTokenSource.Token), this.cancellationTokenSource.Token);
         }
 
+        public string CurrentFilePath => this.memoryMappedFileHandler.CurrentFilePath;
+
         /// <inheritdoc/>
         public void Dispose()
         {

troubleshooting/ETW/Readme.md

@@ -122,7 +122,8 @@ As of version 2.18.0, this SDK ships a "self-diagnostics feature" which captures
 
 The self-diagnostics feature can be enabled/changed/disabled while the process is running.
 The SDK will attempt to read the configuration file every 10 seconds, using a non-exclusive read-only mode.
-The SDK will create or overwrite a file with new logs according to the configuration. 
+Each time this configuration file changes, a new log file will be created according to the configuration. 
+This file will not exceed the configured max size and will be circularly overwritten.
 
 #### Configuration
 
@@ -150,13 +151,15 @@ Example:
 
 #### Configuration Parameters
 
-A `FileSize`-KiB log file named as `ExecutableName.ProcessId.log` (e.g. `foobar.exe.12345.log`) will be generated at the specified directory `LogDirectory`.
+A `FileSize`-KiB log file named as `YearMonthDay-HourMinuteSecond.ExecutableName.ProcessId.log` (e.g. `20010101-120000.foobar.exe.12345.log`) will be generated at the specified directory `LogDirectory`.
+The file name starts with the `DateTime.UtcNow` timestamp of when the file was created.
 
 1. `LogDirectory` is the directory where the output log file will be stored. 
 It can be an absolute path or a relative path to the current directory.
 
 2. `FileSize` is a positive integer, which specifies the log file size in [KiB](https://en.wikipedia.org/wiki/Kibibyte).
 This value must be between 1 MiB and 128 MiB (inclusive), or it will be rounded to the closest upper or lower limit.
+The log file will never exceed this configured size, and will be circularly rewriten.
 
 3. `LogLevel` is the lowest level of the events to be captured. 
 This value must match one of the [fields](https://docs.microsoft.com/dotnet/api/system.diagnostics.tracing.eventlevel#fields) of the `EventLevel` enum.