Add scope info and version to Prometheus exporter (#5086)

examples/AspNetCore/Instrumentation.cs

@@ -22,7 +22,7 @@ public Instrumentation()
  string? version = typeof(Instrumentation).Assembly.GetName().Version?.ToString();
  this.ActivitySource = new ActivitySource(ActivitySourceName, version);
  this.meter = new Meter(MeterName, version);
- this.FreezingDaysCounter = this.meter.CreateCounter<long>("weather.days.freezing", "The number of days where the temperature is below freezing");
+ this.FreezingDaysCounter = this.meter.CreateCounter<long>("weather.days.freezing", description: "The number of days where the temperature is below freezing");
  }
 
  public ActivitySource ActivitySource { get; }

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 * Export OpenMetrics format from Prometheus exporters ([#5107](https:/open-telemetry/opentelemetry-dotnet/pull/5107))
+* For requests with OpenMetrics format, scope info is automatically added ([#5086](https:/open-telemetry/opentelemetry-dotnet/pull/5086))
 
 ## 1.7.0-rc.1
 

src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 * Export OpenMetrics format from Prometheus exporters ([#5107](https:/open-telemetry/opentelemetry-dotnet/pull/5107))
+* For requests with OpenMetrics format, scope info is automatically added ([#5086](https:/open-telemetry/opentelemetry-dotnet/pull/5086))
 
 ## 1.7.0-rc.1
 

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusCollectionManager.cs

@@ -14,6 +14,7 @@ internal sealed class PrometheusCollectionManager
  private readonly int scrapeResponseCacheDurationMilliseconds;
  private readonly Func<Batch<Metric>, ExportResult> onCollectRef;
  private readonly Dictionary<Metric, PrometheusMetric> metricsCache;
+ private readonly HashSet<string> scopes;
  private int metricsCacheCount;
  private byte[] buffer = new byte[85000]; // encourage the object to live in LOH (large object heap)
  private int globalLockState;
@@ -29,6 +30,7 @@ public PrometheusCollectionManager(PrometheusExporter exporter)
  this.scrapeResponseCacheDurationMilliseconds = this.exporter.ScrapeResponseCacheDurationMilliseconds;
  this.onCollectRef = this.OnCollect;
  this.metricsCache = new Dictionary<Metric, PrometheusMetric>();
+ this.scopes = new HashSet<string>();
  }
 
 #if NET6_0_OR_GREATER
@@ -170,6 +172,37 @@ private ExportResult OnCollect(Batch<Metric> metrics)
 
  try
  {
+ this.scopes.Clear();
+
+ foreach (var metric in metrics)
+ {
+ if (PrometheusSerializer.CanWriteMetric(metric))
+ {
+ if (this.scopes.Add(metric.MeterName))
+ {
+ try
+ {
+ cursor = PrometheusSerializer.WriteScopeInfo(this.buffer, cursor, metric.MeterName);
+
+ break;
+ }
+ catch (IndexOutOfRangeException)
+ {
+ if (!this.IncreaseBufferSize())
+ {
+ // there are two cases we might run into the following condition:
+ // 1. we have many metrics to be exported - in this case we probably want
+ // to put some upper limit and allow the user to configure it.
+ // 2. we got an IndexOutOfRangeException which was triggered by some other
+ // code instead of the buffer[cursor++] - in this case we should give up
+ // at certain point rather than allocating like crazy.
+ throw;
+ }
+ }
+ }
+ }
+ }
+
  foreach (var metric in metrics)
  {
  if (!PrometheusSerializer.CanWriteMetric(metric))
@@ -194,12 +227,6 @@ private ExportResult OnCollect(Batch<Metric> metrics)
  {
  if (!this.IncreaseBufferSize())
  {
- // there are two cases we might run into the following condition:
- // 1. we have many metrics to be exported - in this case we probably want
- // to put some upper limit and allow the user to configure it.
- // 2. we got an IndexOutOfRangeException which was triggered by some other
- // code instead of the buffer[cursor++] - in this case we should give up
- // at certain point rather than allocating like crazy.
  throw;
  }
  }

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializer.cs

@@ -5,6 +5,7 @@
 using System.Globalization;
 using System.Runtime.CompilerServices;
 using OpenTelemetry.Internal;
+using OpenTelemetry.Metrics;
 
 namespace OpenTelemetry.Exporter.Prometheus;
 
@@ -313,6 +314,31 @@ public static int WriteUnitMetadata(byte[] buffer, int cursor, PrometheusMetric
  return cursor;
  }
 
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public static int WriteScopeInfo(byte[] buffer, int cursor, string scopeName)
+ {
+ if (string.IsNullOrEmpty(scopeName))
+ {
+ return cursor;
+ }
+
+ cursor = WriteAsciiStringNoEscape(buffer, cursor, "# TYPE otel_scope_info info");
+ buffer[cursor++] = ASCII_LINEFEED;
+
+ cursor = WriteAsciiStringNoEscape(buffer, cursor, "# HELP otel_scope_info Scope metadata");
+ buffer[cursor++] = ASCII_LINEFEED;
+
+ cursor = WriteAsciiStringNoEscape(buffer, cursor, "otel_scope_info");
+ buffer[cursor++] = unchecked((byte)'{');
+ cursor = WriteLabel(buffer, cursor, "otel_scope_name", scopeName);
+ buffer[cursor++] = unchecked((byte)'}');
+ buffer[cursor++] = unchecked((byte)' ');
+ buffer[cursor++] = unchecked((byte)'1');
+ buffer[cursor++] = ASCII_LINEFEED;
+
+ return cursor;
+ }
+
  [MethodImpl(MethodImplOptions.AggressiveInlining)]
  public static int WriteTimestamp(byte[] buffer, int cursor, long value, bool useOpenMetrics)
  {
@@ -339,6 +365,37 @@ public static int WriteTimestamp(byte[] buffer, int cursor, long value, bool use
  return WriteLong(buffer, cursor, value);
  }
 
+ [MethodImpl(MethodImplOptions.AggressiveInlining)]
+ public static int WriteTags(byte[] buffer, int cursor, Metric metric, ReadOnlyTagCollection tags, bool writeEnclosingBraces = true)
+ {
+ if (writeEnclosingBraces)
+ {
+ buffer[cursor++] = unchecked((byte)'{');
+ }
+
+ cursor = WriteLabel(buffer, cursor, "otel_scope_name", metric.MeterName);
+ buffer[cursor++] = unchecked((byte)',');
+
+ if (!string.IsNullOrEmpty(metric.MeterVersion))
+ {
+ cursor = WriteLabel(buffer, cursor, "otel_scope_version", metric.MeterVersion);
+ buffer[cursor++] = unchecked((byte)',');
+ }
+
+ foreach (var tag in tags)
+ {
+ cursor = WriteLabel(buffer, cursor, tag.Key, tag.Value);
+ buffer[cursor++] = unchecked((byte)',');
+ }
+
+ if (writeEnclosingBraces)
+ {
+ buffer[cursor - 1] = unchecked((byte)'}'); // Note: We write the '}' over the last written comma, which is extra.
+ }
+
+ return cursor;
+ }
+
  private static string MapPrometheusType(PrometheusType type)
  {
  return type switch

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs

@@ -32,24 +32,11 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
  {
  foreach (ref readonly var metricPoint in metric.GetMetricPoints())
  {
- var tags = metricPoint.Tags;
  var timestamp = metricPoint.EndTime.ToUnixTimeMilliseconds();
 
  // Counter and Gauge
  cursor = WriteMetricName(buffer, cursor, prometheusMetric);
-
- if (tags.Count > 0)
- {
- buffer[cursor++] = unchecked((byte)'{');
-
- foreach (var tag in tags)
- {
- cursor = WriteLabel(buffer, cursor, tag.Key, tag.Value);
- buffer[cursor++] = unchecked((byte)',');
- }
-
- buffer[cursor - 1] = unchecked((byte)'}'); // Note: We write the '}' over the last written comma, which is extra.
- }
+ cursor = WriteTags(buffer, cursor, metric, metricPoint.Tags);
 
  buffer[cursor++] = unchecked((byte)' ');
 
@@ -100,12 +87,7 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
 
  cursor = WriteMetricName(buffer, cursor, prometheusMetric);
  cursor = WriteAsciiStringNoEscape(buffer, cursor, "_bucket{");
-
- foreach (var tag in tags)
- {
- cursor = WriteLabel(buffer, cursor, tag.Key, tag.Value);
- buffer[cursor++] = unchecked((byte)',');
- }
+ cursor = WriteTags(buffer, cursor, metric, tags, writeEnclosingBraces: false);
 
  cursor = WriteAsciiStringNoEscape(buffer, cursor, "le=\"");
 
@@ -131,19 +113,7 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
  // Histogram sum
  cursor = WriteMetricName(buffer, cursor, prometheusMetric);
  cursor = WriteAsciiStringNoEscape(buffer, cursor, "_sum");
-
- if (tags.Count > 0)
- {
- buffer[cursor++] = unchecked((byte)'{');
-
- foreach (var tag in tags)
- {
- cursor = WriteLabel(buffer, cursor, tag.Key, tag.Value);
- buffer[cursor++] = unchecked((byte)',');
- }
-
- buffer[cursor - 1] = unchecked((byte)'}'); // Note: We write the '}' over the last written comma, which is extra.
- }
+ cursor = WriteTags(buffer, cursor, metric, metricPoint.Tags);
 
  buffer[cursor++] = unchecked((byte)' ');
 
@@ -157,19 +127,7 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
  // Histogram count
  cursor = WriteMetricName(buffer, cursor, prometheusMetric);
  cursor = WriteAsciiStringNoEscape(buffer, cursor, "_count");
-
- if (tags.Count > 0)
- {
- buffer[cursor++] = unchecked((byte)'{');
-
- foreach (var tag in tags)
- {
- cursor = WriteLabel(buffer, cursor, tag.Key, tag.Value);
- buffer[cursor++] = unchecked((byte)',');
- }
-
- buffer[cursor - 1] = unchecked((byte)'}'); // Note: We write the '}' over the last written comma, which is extra.
- }
+ cursor = WriteTags(buffer, cursor, metric, metricPoint.Tags);
 
  buffer[cursor++] = unchecked((byte)' ');
 

test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs

@@ -19,6 +19,8 @@ namespace OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests;
 
 public sealed class PrometheusExporterMiddlewareTests
 {
+ private const string MeterVersion = "1.0.1";
+
  private static readonly string MeterName = Utils.GetCurrentMethodName();
 
  [Fact]
@@ -281,7 +283,7 @@ private static async Task RunPrometheusExporterMiddlewareIntegrationTest(
  new KeyValuePair<string, object>("key2", "value2"),
  };
 
- using var meter = new Meter(MeterName);
+ using var meter = new Meter(MeterName, MeterVersion);
 
  var beginTimestamp = DateTimeOffset.Now.ToUnixTimeMilliseconds();
 
@@ -320,11 +322,17 @@ private static async Task RunPrometheusExporterMiddlewareIntegrationTest(
  string content = await response.Content.ReadAsStringAsync();
 
  string expected = requestOpenMetrics
- ? "# TYPE counter_double_total counter\n"
- + "counter_double_total{key1='value1',key2='value2'} 101.17 (\\d+\\.\\d{3})\n"
+ ? "# TYPE otel_scope_info info\n"
+ + "# HELP otel_scope_info Scope metadata\n"
+ + $"otel_scope_info{{otel_scope_name='{MeterName}'}} 1\n"
+ + "# TYPE counter_double_total counter\n"
+ + $"counter_double_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',key1='value1',key2='value2'}} 101.17 (\\d+\\.\\d{{3}})\n"
  + "# EOF\n"
- : "# TYPE counter_double_total counter\n"
- + "counter_double_total{key1='value1',key2='value2'} 101.17 (\\d+)\n"
+ : "# TYPE otel_scope_info info\n"
+ + "# HELP otel_scope_info Scope metadata\n"
+ + $"otel_scope_info{{otel_scope_name='{MeterName}'}} 1\n"
+ + "# TYPE counter_double_total counter\n"
+ + $"counter_double_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',key1='value1',key2='value2'}} 101.17 (\\d+)\n"
  + "# EOF\n";
 
  var matches = Regex.Matches(content, ("^" + expected + "$").Replace('\'', '"'));

test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs

@@ -14,7 +14,9 @@ namespace OpenTelemetry.Exporter.Prometheus.Tests;
 
 public class PrometheusHttpListenerTests
 {
- private readonly string meterName = Utils.GetCurrentMethodName();
+ private const string MeterVersion = "1.0.1";
+
+ private static readonly string MeterName = Utils.GetCurrentMethodName();
 
  [Theory]
  [InlineData("http://+:9464")]
@@ -99,7 +101,7 @@ private async Task RunPrometheusExporterHttpServerIntegrationTest(bool skipMetri
  string address = null;
 
  MeterProvider provider = null;
- using var meter = new Meter(this.meterName);
+ using var meter = new Meter(MeterName, MeterVersion);
 
  while (retryAttempts-- != 0)
  {
@@ -110,7 +112,10 @@ private async Task RunPrometheusExporterHttpServerIntegrationTest(bool skipMetri
  {
  provider = Sdk.CreateMeterProviderBuilder()
  .AddMeter(meter.Name)
- .AddPrometheusHttpListener(options => options.UriPrefixes = new string[] { address })
+ .AddPrometheusHttpListener(options =>
+ {
+ options.UriPrefixes = new string[] { address };
+ })
  .Build();
 
  break;
@@ -165,11 +170,17 @@ private async Task RunPrometheusExporterHttpServerIntegrationTest(bool skipMetri
  var content = await response.Content.ReadAsStringAsync();
 
  var expected = requestOpenMetrics
- ? "# TYPE counter_double_total counter\n"
- + "counter_double_total{key1='value1',key2='value2'} 101.17 \\d+\\.\\d{3}\n"
+ ? "# TYPE otel_scope_info info\n"
+ + "# HELP otel_scope_info Scope metadata\n"
+ + $"otel_scope_info{{otel_scope_name='{MeterName}'}} 1\n"
+ + "# TYPE counter_double_total counter\n"
+ + $"counter_double_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',key1='value1',key2='value2'}} 101.17 (\\d+\\.\\d{{3}})\n"
  + "# EOF\n"
- : "# TYPE counter_double_total counter\n"
- + "counter_double_total{key1='value1',key2='value2'} 101.17 \\d+\n"
+ : "# TYPE otel_scope_info info\n"
+ + "# HELP otel_scope_info Scope metadata\n"
+ + $"otel_scope_info{{otel_scope_name='{MeterName}'}} 1\n"
+ + "# TYPE counter_double_total counter\n"
+ + $"counter_double_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',key1='value1',key2='value2'}} 101.17 (\\d+)\n"
  + "# EOF\n";
 
  Assert.Matches(("^" + expected + "$").Replace('\'', '"'), content);