Optimized buffer checking & don't check file size if it's going to be truncated

Author: niemyjski

src/Exceptionless/Logging/FileExceptionlessLog.cs

@@ -117,13 +117,14 @@ public void Trace(string message, string source = null) {
         }
 
         public void Flush() {
-            if (_isFlushing || _buffer.Count == 0)
+            if (_isFlushing || _buffer.IsEmpty)
                 return;
 
-            if (DateTime.UtcNow.Subtract(_lastSizeCheck).TotalSeconds > 120)
+            // Only check if appending file and size hasn't been checked in 2 minutes
+            if ((_append || !_firstWrite) && DateTime.UtcNow.Subtract(_lastSizeCheck).TotalSeconds > 120)
                 CheckFileSize();
 
-            if (_isFlushing)
+            if (_isFlushing || _buffer.IsEmpty)
                 return;
 
             try {

test/Exceptionless.Tests/Log/FileExceptionlessLogTestBase.cs

@@ -31,7 +31,7 @@ public virtual async Task LogFlushTimerWorks() {
                 string contents = log.GetFileContents();
                 Assert.Equal("", contents);
 
-                await Task.Delay(TimeSpan.FromMilliseconds(3050));
+                await Task.Delay(TimeSpan.FromMilliseconds(3100));
 
                 Assert.True(LogExists(log.FilePath));
                 contents = log.GetFileContents();