Catch exceptions in flush timer and write to EventSource (#696)

* Catch exceptions in flush timer and write to EventSource

* Fix naming

* Revert OpenTelemetryApiEventSource naming fix

* Remove whitespace changes

* Add missing header

* Change error handling

* Fix

src/OpenTelemetry.Exporter.Jaeger/Implementation/JaegerExporterEventSource.cs

@@ -0,0 +1,81 @@
+// <copyright file="JaegerExporterEventSource.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed 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.
+// </copyright>
+
+using System;
+using System.Diagnostics.Tracing;
+using System.Globalization;
+using System.Threading;
+
+namespace OpenTelemetry.Exporter.Jaeger.Implementation
+{
+    /// <summary>
+    /// EventSource events emitted from the project.
+    /// </summary>
+    [EventSource(Name = "OpenTelemetry-Exporter-Jaeger")]
+    internal class JaegerExporterEventSource : EventSource
+    {
+        public static JaegerExporterEventSource Log = new JaegerExporterEventSource();
+
+        [NonEvent]
+        public void FailedFlush(Exception ex)
+        {
+            if (this.IsEnabled(EventLevel.Error, EventKeywords.All))
+            {
+                this.FailedFlush(ToInvariantString(ex));
+            }
+        }
+
+        [NonEvent]
+        public void UnexpectedError(Exception ex)
+        {
+            if (this.IsEnabled(EventLevel.Error, EventKeywords.All))
+            {
+                this.UnexpectedError(ToInvariantString(ex));
+            }
+        }
+
+        [Event(1, Message = "Failed to send spans: '{0}'", Level = EventLevel.Error)]
+        public void FailedFlush(string exception)
+        {
+            this.WriteEvent(1, exception);
+        }
+
+        [Event(2, Message = "Error: '{0}'", Level = EventLevel.Error)]
+        public void UnexpectedError(string exception)
+        {
+            this.WriteEvent(1, exception);
+        }
+
+        /// <summary>
+        /// Returns a culture-independent string representation of the given <paramref name="exception"/> object,
+        /// appropriate for diagnostics tracing.
+        /// </summary>
+        private static string ToInvariantString(Exception exception)
+        {
+            var originalUICulture = Thread.CurrentThread.CurrentUICulture;
+
+            try
+            {
+                Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;
+                return exception.ToString();
+            }
+            finally
+            {
+                Thread.CurrentThread.CurrentUICulture = originalUICulture;
+            }
+        }
+    }
+}

src/OpenTelemetry.Exporter.Jaeger/Implementation/JaegerUdpBatcher.cs

@@ -72,8 +72,15 @@ namespace OpenTelemetry.Exporter.Jaeger.Implementation
 
             this.maxFlushIntervalTimer.Elapsed += async (sender, args) =>
             {
-                await this.FlushAsyncInternal(false, CancellationToken.None).ConfigureAwait(false);
-            };
+                try
+                {
+                    await this.FlushAsyncInternal(false, CancellationToken.None).ConfigureAwait(false);
+                }
+                catch (Exception ex)
+                {
+                    JaegerExporterEventSource.Log.UnexpectedError(ex);
+                }
+            };
         }
 
         public Process Process { get; internal set; }
@@ -238,6 +245,12 @@ namespace OpenTelemetry.Exporter.Jaeger.Implementation
 
                 return n;
             }
+            catch (Exception ex)
+            {
+                JaegerExporterEventSource.Log.FailedFlush(ex);
+
+                return 0;
+            }
             finally
             {
                 if (!lockAlreadyHeld)