Expose ability to custom timestamp metrics (#158)

* Expose ability to custom timestamp metrics
* Cosmetic fixes.

Author: ryuyu

src/NuGet.Services.Contracts/Logging/ITelemetryClient.cs

@@ -13,6 +13,12 @@ void TrackMetric(
             double value,
             IDictionary<string, string> properties = null);
 
+        void TrackMetric(
+            DateTimeOffset timestamp,
+            string metricName,
+            double value,
+            IDictionary<string, string> properties = null);
+
         void TrackException(
             Exception exception,
             IDictionary<string, string> properties = null,

src/NuGet.Services.Logging/TelemetryClientWrapper.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using Microsoft.ApplicationInsights;
+using Microsoft.ApplicationInsights.DataContracts;
 
 namespace NuGet.Services.Logging
 {
@@ -45,5 +46,36 @@ public void TrackMetric(
                 // logging failed, don't allow exception to escape
             }
         }
+
+        public void TrackMetric(
+            DateTimeOffset timestamp,
+            string metricName,
+            double value,
+            IDictionary<string, string> properties = null)
+        {
+            try
+            {
+                var metricTelemetry = new MetricTelemetry
+                {
+                    Timestamp = timestamp,
+                    Name = metricName,
+                    Value = value
+                };
+
+                if (properties != null)
+                {
+                    foreach (var key in properties.Keys)
+                    {
+                        metricTelemetry.Properties.Add(key, properties[key]);
+                    }
+                }
+
+                _telemetryClient.TrackMetric(metricTelemetry);
+            }
+            catch
+            {
+                // logging failed, don't allow exception to escape
+            }
+        }
     }
 }