Make the log file name unique per session (#50)

* Make the log file name unique per session

* Try to use PID for unique ID

src/Microsoft.SqlTools.ServiceLayer/Utility/Logger.cs

@@ -4,6 +4,7 @@
 //
 
 using System;
+using System.Diagnostics;
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Text;
@@ -54,9 +55,29 @@ namespace Microsoft.SqlTools.EditorServices.Utility
         /// Optional. Specifies the minimum log message level to write to the log file.
         /// </param>
         public static void Initialize(
-            string logFilePath = "SqlToolsService.log",
+            string logFilePath = "sqltools",
             LogLevel minimumLogLevel = LogLevel.Normal)
         {
+            // get a unique number to prevent conflicts of two process launching at the same time
+            int uniqueId;
+            try
+            {
+                uniqueId = Process.GetCurrentProcess().Id;
+            }
+            catch (Exception)
+            {
+                // if the pid look up fails for any reason, just use a random number
+                uniqueId =  new Random().Next(1000, 9999);
+            }
+
+            // make the log path unique
+            string fullFileName = string.Format(
+                "{0}_{1,4:D4}{2,2:D2}{3,2:D2}{4,2:D2}{5,2:D2}{6,2:D2}{7}.log", 
+                logFilePath,
+                DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day,
+                DateTime.Now.Hour, DateTime.Now.Minute, DateTime.Now.Second, 
+                uniqueId);
+
             if (logWriter != null)
             {
                 logWriter.Dispose();
@@ -66,7 +87,7 @@ namespace Microsoft.SqlTools.EditorServices.Utility
             logWriter = 
                 new LogWriter(
                     minimumLogLevel, 
-                    logFilePath,
+                    fullFileName,
                     true);
         }
 

test/Microsoft.SqlTools.ServiceLayer.Test/ServiceHost/LoggerTests.cs

@@ -0,0 +1,62 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.IO;
+using System.Linq;
+using Microsoft.SqlTools.EditorServices.Utility;
+using Xunit;
+
+namespace Microsoft.SqlTools.ServiceLayer.Test.ServiceHost
+{
+    /// <summary>
+    /// Logger test cases
+    /// </summary>
+    public class LoggerTests
+    {
+       
+        /// <summary>
+        /// Test to verify that the logger initialization is generating a valid file
+        /// </summary>
+        [Fact]
+        public void LoggerDefaultFile()
+        {
+            // delete any existing log files from the current directory 
+            Directory.GetFiles(Directory.GetCurrentDirectory())
+                .Where(fileName 
+                     => fileName.Contains("sqltools_") 
+                     && fileName.EndsWith(".log", StringComparison.OrdinalIgnoreCase))
+                .ToList()
+                .ForEach(fileName => File.Delete(fileName));
+
+            // initialize the logger
+            Logger.Initialize(
+                logFilePath: Path.Combine(Directory.GetCurrentDirectory(), "sqltools"),
+                minimumLogLevel: LogLevel.Verbose);
+
+            // close the logger
+            Logger.Close();
+
+            // find the name of the new log file
+            string logFileName = Directory.GetFiles(Directory.GetCurrentDirectory())
+                .Where(fileName 
+                     => fileName.Contains("sqltools_") 
+                     && fileName.EndsWith(".log", StringComparison.OrdinalIgnoreCase)).SingleOrDefault();
+                
+            // validate the log file was created with desired name 
+            Assert.True(!string.IsNullOrWhiteSpace(logFileName));
+            if (!string.IsNullOrWhiteSpace(logFileName))
+            {
+                Assert.True(logFileName.Length > "sqltools_.log".Length);
+                Assert.True(File.Exists(logFileName));
+
+                // delete the test log file
+                if (File.Exists(logFileName))
+                {
+                    File.Delete(logFileName);
+                }
+            }
+        }
+    }
+}