From 0d0bfb3e3ebf8f0648a603fd37fcd7c026ba2148 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Thu, 27 Oct 2022 17:27:26 -0700
Subject: [PATCH 01/10] Support long event source names better in EventCounters
 instrumentation

---
 .../EventCountersMetrics.cs                   | 63 +++++++++++++++-
 .../EventCountersMetricsTests.cs              | 74 +++++++++++++++++--
 2 files changed, 130 insertions(+), 7 deletions(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index c236463144..efa8e0d4ed 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -19,6 +19,7 @@
 using System.Collections.Generic;
 using System.Diagnostics.Metrics;
 using System.Diagnostics.Tracing;
+using System.Text;
 
 namespace OpenTelemetry.Instrumentation.EventCounters;
 
@@ -29,11 +30,13 @@ internal sealed class EventCountersMetrics : EventListener
 {
     internal static readonly Meter MeterInstance = new(typeof(EventCountersMetrics).Assembly.GetName().Name, typeof(EventCountersMetrics).Assembly.GetName().Version.ToString());
 
+    private const string Prefix = "ec";
+    private const int MaxInstrumentNameLength = 63;
+
     private readonly EventCountersInstrumentationOptions options;
     private readonly List<EventSource> preInitEventSources = new();
     private readonly ConcurrentDictionary<(string, string), Instrument> instruments = new();
     private readonly ConcurrentDictionary<(string, string), double> values = new();
-
     /// <summary>
     /// Initializes a new instance of the <see cref="EventCountersMetrics"/> class.
     /// </summary>
@@ -120,6 +123,62 @@ protected override void OnEventWritten(EventWrittenEventArgs eventData)
     private static Dictionary<string, string> GetEnableEventsArguments(EventCountersInstrumentationOptions options) =>
         new() { { "EventCounterIntervalSec", options.RefreshIntervalSecs.ToString() } };
 
+    /// <summary>
+    /// If instrument name is too long, abbreviates event source name.
+    /// E.g. instrument for `Microsoft-AspNetCore-Server-Kestrel`, `tls-handshakes-per-second`
+    /// would be too long (64 chars), so it's abbreviated to `ec.m.a.s.k.tls-handshakes-per-second`
+    /// instead of `ec.Microsoft-AspNetCore-Server-Kestrel.tls-handshakes-per-second`.
+    ///
+    /// If after that instrument name is still invalid, it will be validated and ignored later in the pipeline.
+    /// </summary>
+    private static string GetInstrumentName(string sourceName, string eventName)
+    {
+        int totalLength = Prefix.Length + 1 + sourceName.Length + 1 + eventName.Length;
+        if (totalLength <= MaxInstrumentNameLength)
+        {
+            return string.Concat(Prefix, ".", sourceName, ".", eventName);
+        }
+
+        int maxEventSourceNameLength = MaxInstrumentNameLength - Prefix.Length - 2 - eventName.Length;
+        var abbreviation = new StringBuilder(maxEventSourceNameLength);
+        int ind = 0;
+        while (ind >= 0 && ind < sourceName.Length)
+        {
+            while (ind < sourceName.Length && (sourceName[ind] == '.' || sourceName[ind] == '-'))
+            {
+                ind++;
+            }
+
+            if (ind < sourceName.Length)
+            {
+                abbreviation.Append(char.ToLowerInvariant(sourceName[ind])).Append('.');
+            }
+
+            int nextDot = sourceName.IndexOf('.', ind);
+            int nextDash = sourceName.IndexOf('-', ind);
+
+            if (nextDot < 0)
+            {
+                if (nextDash < 0)
+                {
+                    break;
+                }
+
+                ind = nextDash;
+            }
+            else if (nextDash < 0)
+            {
+                ind = nextDot;
+            }
+            else
+            {
+                ind = Math.Min(nextDot, nextDash);
+            }
+        }
+
+        return string.Concat(Prefix, ".", abbreviation.ToString(), eventName);
+    }
+
     private void EnableEvents(EventSource eventSource)
     {
         this.EnableEvents(eventSource, EventLevel.Critical, EventKeywords.None, GetEnableEventsArguments(this.options));
@@ -132,7 +191,7 @@ private void UpdateInstrumentWithEvent(bool isGauge, string eventSourceName, str
             ValueTuple<string, string> metricKey = new(eventSourceName, name);
             _ = this.values.AddOrUpdate(metricKey, value, isGauge ? (_, _) => value : (_, existing) => existing + value);
 
-            var instrumentName = $"EventCounters.{eventSourceName}.{name}";
+            var instrumentName = GetInstrumentName(eventSourceName, name);
 
             if (!this.instruments.ContainsKey(metricKey))
             {
diff --git a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
index 26beba4deb..1c3069c410 100644
--- a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
+++ b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
@@ -17,6 +17,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.Tracing;
+using System.Linq;
 using System.Threading.Tasks;
 using OpenTelemetry.Metrics;
 using Xunit;
@@ -68,7 +69,7 @@ public async Task EventCounter()
         meterProvider.ForceFlush();
 
         // Assert
-        var metric = metricItems.Find(x => x.Name == "EventCounters.a.c");
+        var metric = metricItems.Find(x => x.Name == "ec.a.c");
         Assert.NotNull(metric);
         Assert.Equal(MetricType.DoubleGauge, metric.MetricType);
         Assert.Equal(1997.0202, GetActualValue(metric));
@@ -98,7 +99,7 @@ public async Task IncrementingEventCounter()
         meterProvider.ForceFlush();
 
         // Assert
-        var metric = metricItems.Find(x => x.Name == "EventCounters.b.inc-c");
+        var metric = metricItems.Find(x => x.Name == "ec.b.inc-c");
         Assert.NotNull(metric);
         Assert.Equal(MetricType.DoubleSum, metric.MetricType);
         Assert.Equal(3, GetActualValue(metric));
@@ -126,7 +127,7 @@ public async Task PollingCounter()
         meterProvider.ForceFlush();
 
         // Assert
-        var metric = metricItems.Find(x => x.Name == "EventCounters.c.poll-c");
+        var metric = metricItems.Find(x => x.Name == "ec.c.poll-c");
         Assert.NotNull(metric);
         Assert.Equal(MetricType.DoubleGauge, metric.MetricType);
         Assert.Equal(20, GetActualValue(metric));
@@ -154,7 +155,7 @@ public async Task IncrementingPollingCounter()
         meterProvider.ForceFlush();
 
         // Assert
-        var metric = metricItems.Find(x => x.Name == "EventCounters.d.inc-poll-c");
+        var metric = metricItems.Find(x => x.Name == "ec.d.inc-poll-c");
         Assert.NotNull(metric);
         Assert.Equal(MetricType.DoubleSum, metric.MetricType);
         Assert.Equal(2, GetActualValue(metric));
@@ -184,7 +185,7 @@ public async Task EventCounterSameNameUsesNewestCreated()
         meterProvider.ForceFlush();
 
         // Assert
-        var metric = metricItems.Find(x => x.Name == "EventCounters.a.c");
+        var metric = metricItems.Find(x => x.Name == "ec.a.c");
         Assert.NotNull(metric);
         Assert.Equal(MetricType.DoubleGauge, metric.MetricType);
 
@@ -214,6 +215,69 @@ public void ThrowExceptionForUnsupportedEventSources()
         Assert.Equal("Use the `OpenTelemetry.Instrumentation.Runtime` or `OpenTelemetry.Instrumentation.Process` instrumentations.", ex.Message);
     }
 
+    [Theory]
+    [InlineData("Microsoft-AspNetCore-Server-Kestrel-1", "tls-handshakes-per-second", "ec.m.a.s.k.1.tls-handshakes-per-second")]
+    [InlineData("Microsoft-AspNetCore-Server-Kestrel-1", "tls-handshakes-per-sec", "ec.Microsoft-AspNetCore-Server-Kestrel-1.tls-handshakes-per-sec")]
+    [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-stopped", "ec.Microsoft.AspNetCore.Http.Connections-1.connections-stopped")]
+    [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-timed-out-longer", "ec.m.a.h.c.1.connections-timed-out-longer")]
+    public async Task EventSourceNameAbbreviation(string sourceName, string eventName, string expectedInstrumentName)
+    {
+        // Arrange
+        List<Metric> metricItems = new();
+        EventSource source = new(sourceName);
+        IncrementingEventCounter connections = new(eventName, source);
+
+        var meterProvider = Sdk.CreateMeterProviderBuilder()
+            .AddEventCountersInstrumentation(options =>
+            {
+                options.AddEventSources(source.Name);
+            })
+            .AddInMemoryExporter(metricItems)
+            .Build();
+
+        // Act
+        connections.Increment(1);
+        await Task.Delay(Delay);
+        meterProvider.ForceFlush();
+
+        // Assert
+        Metric metric = metricItems.Find(m => m.Name == expectedInstrumentName);
+        Assert.NotNull(metric);
+        Assert.Equal(1, GetActualValue(metric));
+    }
+
+    [Fact]
+    public async Task InstrumentNameTooLong()
+    {
+        // Arrange
+        List<Metric> metricItems = new();
+        EventSource source = new("source");
+
+        // ec.s. + event name is 63;
+        string veryLongEventName = new string('e', 59);
+        IncrementingEventCounter connections = new(veryLongEventName, source);
+
+        var meterProvider = Sdk.CreateMeterProviderBuilder()
+            .AddEventCountersInstrumentation(options =>
+            {
+                options.AddEventSources(source.Name);
+            })
+            .AddInMemoryExporter(metricItems)
+            .Build();
+
+        // Act
+        connections.Increment(1);
+        await Task.Delay(Delay);
+        meterProvider.ForceFlush();
+
+        // Assert
+        foreach (var item in metricItems)
+        {
+            Assert.False(item.Name.StartsWith("ec.source.ee"));
+            Assert.False(item.Name.StartsWith("ec.s.ee"));
+        }
+    }
+
     // polling and eventcounter with same instrument name?
 
     private static double GetActualValue(Metric metric)

From e302ad9e4e0946d503dec8282bfea7c7d5646bff Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Thu, 27 Oct 2022 17:41:12 -0700
Subject: [PATCH 02/10] lint

---
 .../EventCountersMetrics.cs                                      | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index efa8e0d4ed..deec1840e7 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -37,6 +37,7 @@ internal sealed class EventCountersMetrics : EventListener
     private readonly List<EventSource> preInitEventSources = new();
     private readonly ConcurrentDictionary<(string, string), Instrument> instruments = new();
     private readonly ConcurrentDictionary<(string, string), double> values = new();
+
     /// <summary>
     /// Initializes a new instance of the <see cref="EventCountersMetrics"/> class.
     /// </summary>

From 941acad59d6cfa66dbbd85aac28d4bc93274fdd7 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Wed, 9 Nov 2022 09:36:28 -0800
Subject: [PATCH 03/10] review

---
 .../CHANGELOG.md                                            | 3 +++
 .../EventCountersMetrics.cs                                 | 6 ++----
 .../EventCountersMetricsTests.cs                            | 2 +-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
index f3f36b2d94..aecb87cb95 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
@@ -3,6 +3,9 @@
 ## Unreleased
 
 * Update OpenTelemetry.Api to 1.3.1.
+* Changed `EventCounter` prefix to `ec` and started abbreviating event source name
+  when instrument name is longer that 63 characters.
+  ([#740](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/740))
 
 ## 1.0.0-alpha.1
 
diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index deec1840e7..9096e20ed1 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -140,8 +140,7 @@ private static string GetInstrumentName(string sourceName, string eventName)
             return string.Concat(Prefix, ".", sourceName, ".", eventName);
         }
 
-        int maxEventSourceNameLength = MaxInstrumentNameLength - Prefix.Length - 2 - eventName.Length;
-        var abbreviation = new StringBuilder(maxEventSourceNameLength);
+        var abbreviation = new StringBuilder(sourceName.Length);
         int ind = 0;
         while (ind >= 0 && ind < sourceName.Length)
         {
@@ -192,10 +191,9 @@ private void UpdateInstrumentWithEvent(bool isGauge, string eventSourceName, str
             ValueTuple<string, string> metricKey = new(eventSourceName, name);
             _ = this.values.AddOrUpdate(metricKey, value, isGauge ? (_, _) => value : (_, existing) => existing + value);
 
-            var instrumentName = GetInstrumentName(eventSourceName, name);
-
             if (!this.instruments.ContainsKey(metricKey))
             {
+                var instrumentName = GetInstrumentName(eventSourceName, name);
                 Instrument instrument = isGauge
                     ? MeterInstance.CreateObservableGauge(instrumentName, () => this.values[metricKey])
                     : MeterInstance.CreateObservableCounter(instrumentName, () => this.values[metricKey]);
diff --git a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
index 1c3069c410..4f7736469c 100644
--- a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
+++ b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
@@ -254,7 +254,7 @@ public async Task InstrumentNameTooLong()
         EventSource source = new("source");
 
         // ec.s. + event name is 63;
-        string veryLongEventName = new string('e', 59);
+        string veryLongEventName = new string('e', 100);
         IncrementingEventCounter connections = new(veryLongEventName, source);
 
         var meterProvider = Sdk.CreateMeterProviderBuilder()

From 807463b7df89174497808849516e32a7defb2648 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Wed, 9 Nov 2022 18:07:38 -0800
Subject: [PATCH 04/10] shorten source name if abbreviation is not enough

---
 .../EventCountersMetrics.cs                       | 15 ++++++++++++++-
 .../EventCountersMetricsTests.cs                  |  3 +++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index 9096e20ed1..18ed7441da 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -140,7 +140,15 @@ private static string GetInstrumentName(string sourceName, string eventName)
             return string.Concat(Prefix, ".", sourceName, ".", eventName);
         }
 
-        var abbreviation = new StringBuilder(sourceName.Length);
+        var maxEventSourceLength = MaxInstrumentNameLength - Prefix.Length - 1 - eventName.Length;
+        if (maxEventSourceLength < 2) 
+        {
+            // event name is too long, there is not enough space for sourceName.
+            // let ec.<eventName> flow to metrics SDK and filter if needed.
+            return string.Concat(Prefix, ".", eventName);
+        }
+
+        var abbreviation = new StringBuilder(maxEventSourceLength);
         int ind = 0;
         while (ind >= 0 && ind < sourceName.Length)
         {
@@ -151,6 +159,11 @@ private static string GetInstrumentName(string sourceName, string eventName)
 
             if (ind < sourceName.Length)
             {
+                if (abbreviation.Length + 2 >= maxEventSourceLength)
+                {
+                    break;
+                }
+
                 abbreviation.Append(char.ToLowerInvariant(sourceName[ind])).Append('.');
             }
 
diff --git a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
index 4f7736469c..737c9d35ea 100644
--- a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
+++ b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
@@ -220,6 +220,9 @@ public void ThrowExceptionForUnsupportedEventSources()
     [InlineData("Microsoft-AspNetCore-Server-Kestrel-1", "tls-handshakes-per-sec", "ec.Microsoft-AspNetCore-Server-Kestrel-1.tls-handshakes-per-sec")]
     [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-stopped", "ec.Microsoft.AspNetCore.Http.Connections-1.connections-stopped")]
     [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-timed-out-longer", "ec.m.a.h.c.1.connections-timed-out-longer")]
+    [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-very-very-long-event-name", "ec.very-very-very-very-very-very-very-very-very-long-event-name")]
+    [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-very-long-event-name", "ec.m.a.very-very-very-very-very-very-very-very-long-event-name")]
+    [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-long-event-name", "ec.m.a.o.t.very-very-very-very-very-very-very-long-event-name")]
     public async Task EventSourceNameAbbreviation(string sourceName, string eventName, string expectedInstrumentName)
     {
         // Arrange

From 218e9560ab894025f66d2bdd4ac6eb9a59b3a97c Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Wed, 9 Nov 2022 18:16:01 -0800
Subject: [PATCH 05/10] lint

---
 .../CHANGELOG.md                                          | 4 ++--
 .../EventCountersMetrics.cs                               | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
index aecb87cb95..0bc56cdbaf 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
@@ -3,8 +3,8 @@
 ## Unreleased
 
 * Update OpenTelemetry.Api to 1.3.1.
-* Changed `EventCounter` prefix to `ec` and started abbreviating event source name
-  when instrument name is longer that 63 characters.
+* Change `EventCounter` prefix to `ec` and abbreviate event source name
+  when instrument name is longer than 63 characters.
   ([#740](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/740))
 
 ## 1.0.0-alpha.1
diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index 18ed7441da..7fa32ee95d 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -141,10 +141,10 @@ private static string GetInstrumentName(string sourceName, string eventName)
         }
 
         var maxEventSourceLength = MaxInstrumentNameLength - Prefix.Length - 1 - eventName.Length;
-        if (maxEventSourceLength < 2) 
+        if (maxEventSourceLength < 2)
         {
             // event name is too long, there is not enough space for sourceName.
-            // let ec.<eventName> flow to metrics SDK and filter if needed.
+            // let ec.<eventName> flow to metrics SDK and it will suppress it if needed.
             return string.Concat(Prefix, ".", eventName);
         }
 
@@ -159,12 +159,12 @@ private static string GetInstrumentName(string sourceName, string eventName)
 
             if (ind < sourceName.Length)
             {
+                abbreviation.Append(char.ToLowerInvariant(sourceName[ind])).Append('.');
                 if (abbreviation.Length + 2 >= maxEventSourceLength)
                 {
+                    // stop if there is no room to add another letter and a dot after
                     break;
                 }
-
-                abbreviation.Append(char.ToLowerInvariant(sourceName[ind])).Append('.');
             }
 
             int nextDot = sourceName.IndexOf('.', ind);

From 3519fe293369980b467d1c77e0290b2d32f7b607 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Thu, 10 Nov 2022 16:01:57 -0800
Subject: [PATCH 06/10] shortening instead of abbreviation

---
 .../EventCountersMetrics.cs                   | 44 +------------------
 .../EventCountersMetricsTests.cs              | 10 ++---
 2 files changed, 6 insertions(+), 48 deletions(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index 7fa32ee95d..71a6b1cac1 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -19,7 +19,6 @@
 using System.Collections.Generic;
 using System.Diagnostics.Metrics;
 using System.Diagnostics.Tracing;
-using System.Text;
 
 namespace OpenTelemetry.Instrumentation.EventCounters;
 
@@ -148,48 +147,7 @@ private static string GetInstrumentName(string sourceName, string eventName)
             return string.Concat(Prefix, ".", eventName);
         }
 
-        var abbreviation = new StringBuilder(maxEventSourceLength);
-        int ind = 0;
-        while (ind >= 0 && ind < sourceName.Length)
-        {
-            while (ind < sourceName.Length && (sourceName[ind] == '.' || sourceName[ind] == '-'))
-            {
-                ind++;
-            }
-
-            if (ind < sourceName.Length)
-            {
-                abbreviation.Append(char.ToLowerInvariant(sourceName[ind])).Append('.');
-                if (abbreviation.Length + 2 >= maxEventSourceLength)
-                {
-                    // stop if there is no room to add another letter and a dot after
-                    break;
-                }
-            }
-
-            int nextDot = sourceName.IndexOf('.', ind);
-            int nextDash = sourceName.IndexOf('-', ind);
-
-            if (nextDot < 0)
-            {
-                if (nextDash < 0)
-                {
-                    break;
-                }
-
-                ind = nextDash;
-            }
-            else if (nextDash < 0)
-            {
-                ind = nextDot;
-            }
-            else
-            {
-                ind = Math.Min(nextDot, nextDash);
-            }
-        }
-
-        return string.Concat(Prefix, ".", abbreviation.ToString(), eventName);
+        return string.Concat(Prefix, ".", sourceName.Substring(0, maxEventSourceLength - 1), ".", eventName);
     }
 
     private void EnableEvents(EventSource eventSource)
diff --git a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
index 737c9d35ea..2529fd3d1e 100644
--- a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
+++ b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
@@ -216,14 +216,14 @@ public void ThrowExceptionForUnsupportedEventSources()
     }
 
     [Theory]
-    [InlineData("Microsoft-AspNetCore-Server-Kestrel-1", "tls-handshakes-per-second", "ec.m.a.s.k.1.tls-handshakes-per-second")]
+    [InlineData("Microsoft-AspNetCore-Server-Kestrel-1", "tls-handshakes-per-second", "ec.Microsoft-AspNetCore-Server-Kestre.tls-handshakes-per-second")]
     [InlineData("Microsoft-AspNetCore-Server-Kestrel-1", "tls-handshakes-per-sec", "ec.Microsoft-AspNetCore-Server-Kestrel-1.tls-handshakes-per-sec")]
     [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-stopped", "ec.Microsoft.AspNetCore.Http.Connections-1.connections-stopped")]
-    [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-timed-out-longer", "ec.m.a.h.c.1.connections-timed-out-longer")]
+    [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-timed-out-longer", "ec.Microsoft.AspNetCore.Http.Conne.connections-timed-out-longer")]
     [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-very-very-long-event-name", "ec.very-very-very-very-very-very-very-very-very-long-event-name")]
-    [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-very-long-event-name", "ec.m.a.very-very-very-very-very-very-very-very-long-event-name")]
-    [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-long-event-name", "ec.m.a.o.t.very-very-very-very-very-very-very-long-event-name")]
-    public async Task EventSourceNameAbbreviation(string sourceName, string eventName, string expectedInstrumentName)
+    [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-very-long-event-name", "ec.Micr.very-very-very-very-very-very-very-very-long-event-name")]
+    [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-long-event-name", "ec.Microsoft.very-very-very-very-very-very-very-long-event-name")]
+    public async Task EventSourceNameShortening(string sourceName, string eventName, string expectedInstrumentName)
     {
         // Arrange
         List<Metric> metricItems = new();

From 7c8248e4b2d6cd9e06f66bf5bd5c328a1aadd1ff Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Thu, 10 Nov 2022 16:06:49 -0800
Subject: [PATCH 07/10] nits

---
 .../EventCountersMetrics.cs                               | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index 71a6b1cac1..c71be7c85f 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -126,10 +126,10 @@ private static Dictionary<string, string> GetEnableEventsArguments(EventCounters
     /// <summary>
     /// If instrument name is too long, abbreviates event source name.
     /// E.g. instrument for `Microsoft-AspNetCore-Server-Kestrel`, `tls-handshakes-per-second`
-    /// would be too long (64 chars), so it's abbreviated to `ec.m.a.s.k.tls-handshakes-per-second`
-    /// instead of `ec.Microsoft-AspNetCore-Server-Kestrel.tls-handshakes-per-second`.
-    ///
-    /// If after that instrument name is still invalid, it will be validated and ignored later in the pipeline.
+    /// would be too long (64 chars), so it's shortened to `ec.Microsoft-AspNetCore-Server-Kestre.tls-handshakes-per-second`.
+    /// 
+    /// If there is no room for event source name, returns `ec.{event name}` and 
+    /// if it's still too long, it will be validated and ignored later in the pipeline.
     /// </summary>
     private static string GetInstrumentName(string sourceName, string eventName)
     {

From 28bdab2c0379b7cc27c293decaddfa13f6ea3f54 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Thu, 10 Nov 2022 16:45:03 -0800
Subject: [PATCH 08/10] review comments

---
 .../CHANGELOG.md                               |  3 +--
 .../EventCountersMetrics.cs                    | 18 ++++++++++++------
 .../EventCountersMetricsTests.cs               |  1 +
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
index 0bc56cdbaf..31fee80f79 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
@@ -3,8 +3,7 @@
 ## Unreleased
 
 * Update OpenTelemetry.Api to 1.3.1.
-* Change `EventCounter` prefix to `ec` and abbreviate event source name
-  when instrument name is longer than 63 characters.
+* Change `EventCounter` prefix to `ec` and trim the event source name to keep instrument name under 63 characters.
   ([#740](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/740))
 
 ## 1.0.0-alpha.1
diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index c71be7c85f..aab398e64d 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -124,11 +124,12 @@ private static Dictionary<string, string> GetEnableEventsArguments(EventCounters
         new() { { "EventCounterIntervalSec", options.RefreshIntervalSecs.ToString() } };
 
     /// <summary>
-    /// If instrument name is too long, abbreviates event source name.
+    /// If the resulting instrument name is too long, it trims the event source name
+    /// to fit in as many characters as possible keeping the event name intact.
     /// E.g. instrument for `Microsoft-AspNetCore-Server-Kestrel`, `tls-handshakes-per-second`
     /// would be too long (64 chars), so it's shortened to `ec.Microsoft-AspNetCore-Server-Kestre.tls-handshakes-per-second`.
-    /// 
-    /// If there is no room for event source name, returns `ec.{event name}` and 
+    ///
+    /// If there is no room for event source name, returns `ec.{event name}` and
     /// if it's still too long, it will be validated and ignored later in the pipeline.
     /// </summary>
     private static string GetInstrumentName(string sourceName, string eventName)
@@ -139,15 +140,20 @@ private static string GetInstrumentName(string sourceName, string eventName)
             return string.Concat(Prefix, ".", sourceName, ".", eventName);
         }
 
-        var maxEventSourceLength = MaxInstrumentNameLength - Prefix.Length - 1 - eventName.Length;
-        if (maxEventSourceLength < 2)
+        var maxEventSourceLength = MaxInstrumentNameLength - Prefix.Length - 2 - eventName.Length;
+        if (maxEventSourceLength < 1)
         {
             // event name is too long, there is not enough space for sourceName.
             // let ec.<eventName> flow to metrics SDK and it will suppress it if needed.
             return string.Concat(Prefix, ".", eventName);
         }
 
-        return string.Concat(Prefix, ".", sourceName.Substring(0, maxEventSourceLength - 1), ".", eventName);
+        while (maxEventSourceLength > 0 && (sourceName[maxEventSourceLength - 1] == '.' || sourceName[maxEventSourceLength - 1] == '-'))  
+        {
+            maxEventSourceLength --;
+        }
+
+        return string.Concat(Prefix, ".", sourceName.Substring(0, maxEventSourceLength), ".", eventName);
     }
 
     private void EnableEvents(EventSource eventSource)
diff --git a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
index 2529fd3d1e..dba23b470f 100644
--- a/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
+++ b/test/OpenTelemetry.Instrumentation.EventCounters.Tests/EventCountersMetricsTests.cs
@@ -220,6 +220,7 @@ public void ThrowExceptionForUnsupportedEventSources()
     [InlineData("Microsoft-AspNetCore-Server-Kestrel-1", "tls-handshakes-per-sec", "ec.Microsoft-AspNetCore-Server-Kestrel-1.tls-handshakes-per-sec")]
     [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-stopped", "ec.Microsoft.AspNetCore.Http.Connections-1.connections-stopped")]
     [InlineData("Microsoft.AspNetCore.Http.Connections-1", "connections-timed-out-longer", "ec.Microsoft.AspNetCore.Http.Conne.connections-timed-out-longer")]
+    [InlineData("Microsoft.AspNetCore.Http.Conn.Something", "connections-timed-out-longer", "ec.Microsoft.AspNetCore.Http.Conn.connections-timed-out-longer")]
     [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-very-very-long-event-name", "ec.very-very-very-very-very-very-very-very-very-long-event-name")]
     [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-very-long-event-name", "ec.Micr.very-very-very-very-very-very-very-very-long-event-name")]
     [InlineData("Microsoft.AspNetCore.One.Two", "very-very-very-very-very-very-very-long-event-name", "ec.Microsoft.very-very-very-very-very-very-very-long-event-name")]

From 767cc3777794e1358210b65e9f34276ac5f8f673 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Thu, 10 Nov 2022 17:04:16 -0800
Subject: [PATCH 09/10] lint

---
 .../EventCountersMetrics.cs                                   | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
index aab398e64d..fe8f89dacc 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/EventCountersMetrics.cs
@@ -148,9 +148,9 @@ private static string GetInstrumentName(string sourceName, string eventName)
             return string.Concat(Prefix, ".", eventName);
         }
 
-        while (maxEventSourceLength > 0 && (sourceName[maxEventSourceLength - 1] == '.' || sourceName[maxEventSourceLength - 1] == '-'))  
+        while (maxEventSourceLength > 0 && (sourceName[maxEventSourceLength - 1] == '.' || sourceName[maxEventSourceLength - 1] == '-'))
         {
-            maxEventSourceLength --;
+            maxEventSourceLength--;
         }
 
         return string.Concat(Prefix, ".", sourceName.Substring(0, maxEventSourceLength), ".", eventName);

From 5803f8a1195deae98c8b2dd76d2b4539784bb18d Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <limolkova@microsoft.com>
Date: Thu, 10 Nov 2022 17:15:03 -0800
Subject: [PATCH 10/10] lint

---
 src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
index 31fee80f79..f58d0aeb96 100644
--- a/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
+++ b/src/OpenTelemetry.Instrumentation.EventCounters/CHANGELOG.md
@@ -3,7 +3,8 @@
 ## Unreleased
 
 * Update OpenTelemetry.Api to 1.3.1.
-* Change `EventCounter` prefix to `ec` and trim the event source name to keep instrument name under 63 characters.
+* Change `EventCounter` prefix to `ec` and trim the event source name to keep
+  instrument name under 63 characters.
   ([#740](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/740))
 
 ## 1.0.0-alpha.1