Improve log message for unsupported Instrument (#3124)

docs/metrics/extending-the-sdk/README.md

@@ -54,8 +54,8 @@ class MyExporter : BaseExporter<Metric>
 }
 ```
 
-A demo exporter which simply writes metric name and metric point start time
-, tags to the console is shown [here](./MyExporter.cs).
+A demo exporter which simply writes metric name, metric point start time
+and tags to the console is shown [here](./MyExporter.cs).
 
 Apart from the exporter itself, you should also provide extension methods as
 shown [here](./MyExporterExtensions.cs). This allows users to add the Exporter

src/OpenTelemetry/Metrics/MeterProviderSdk.cs

@@ -207,7 +207,7 @@ namespace OpenTelemetry.Metrics
                             }
                         }
 
-                        OpenTelemetrySdkEventSource.Log.MeterProviderSdkEvent($"Succeeded publishing Instrument = \"{instrument.Name}\" of Meter = \"{instrument.Meter.Name}\".");
+                        OpenTelemetrySdkEventSource.Log.MeterProviderSdkEvent($"Completed publishing Instrument = \"{instrument.Name}\" of Meter = \"{instrument.Meter.Name}\".");
                     }
                     catch (Exception)
                     {
@@ -272,7 +272,7 @@ namespace OpenTelemetry.Metrics
                             }
                         }
 
-                        OpenTelemetrySdkEventSource.Log.MeterProviderSdkEvent($"Succeeded publishing Instrument = \"{instrument.Name}\" of Meter = \"{instrument.Meter.Name}\".");
+                        OpenTelemetrySdkEventSource.Log.MeterProviderSdkEvent($"Completed publishing Instrument = \"{instrument.Name}\" of Meter = \"{instrument.Meter.Name}\".");
                     }
                     catch (Exception)
                     {

src/OpenTelemetry/Metrics/MetricReaderExt.cs

@@ -67,7 +67,21 @@ namespace OpenTelemetry.Metrics
                 }
                 else
                 {
-                    var metric = new Metric(instrumentIdentity, this.Temporality, this.maxMetricPointsPerMetricStream);
+                    Metric metric = null;
+                    try
+                    {
+                        metric = new Metric(instrumentIdentity, this.Temporality, this.maxMetricPointsPerMetricStream);
+                    }
+                    catch (NotSupportedException nse)
+                    {
+                        // TODO: This allocates string even if none listening.
+                        // Could be improved with separate Event.
+                        // Also the message could call out what Instruments
+                        // and types (eg: int, long etc) are supported.
+                        OpenTelemetrySdkEventSource.Log.MetricInstrumentIgnored(metricName, instrument.Meter.Name, "Unsupported instrument. Details: " + nse.Message, "Switch to a supported instrument type.");
+                        return null;
+                    }
+
                     this.instrumentIdentityToMetric[instrumentIdentity] = metric;
                     this.metrics[index] = metric;
                     this.metricStreamNames.Add(metricStreamName);

test/OpenTelemetry.Tests/Metrics/MetricAPITest.cs

@@ -18,7 +18,9 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Diagnostics.Metrics;
+using System.Linq;
 using System.Threading;
+using OpenTelemetry.Internal;
 using OpenTelemetry.Tests;
 using Xunit;
 using Xunit.Abstractions;
@@ -1306,6 +1308,30 @@ namespace OpenTelemetry.Metrics.Tests
             counter.Add(10, new KeyValuePair<string, object>("key", "value"));
         }
 
+        [Fact]
+        public void UnsupportedMetricInstrument()
+        {
+            using var meter = new Meter($"{Utils.GetCurrentMethodName()}");
+            var exportedItems = new List<Metric>();
+            using var meterProvider = Sdk.CreateMeterProviderBuilder()
+            .AddMeter(meter.Name)
+            .AddInMemoryExporter(exportedItems)
+            .Build();
+
+            using (var inMemoryEventListener = new InMemoryEventListener(OpenTelemetrySdkEventSource.Log))
+            {
+                var counter = meter.CreateCounter<decimal>("counter");
+                counter.Add(1);
+
+                // This validates that we log InstrumentIgnored event
+                // and not something else.
+                Assert.Single(inMemoryEventListener.Events.Where((e) => e.EventId == 33));
+            }
+
+            meterProvider.ForceFlush(MaxTimeToAllowForFlush);
+            Assert.Empty(exportedItems);
+        }
+
         private static void ValidateMetricPointTags(List<KeyValuePair<string, object>> expectedTags, ReadOnlyTagCollection actualTags)
         {
             int tagIndex = 0;