[Exporter.Prometheus] Improve performance

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/OpenTelemetry.Exporter.Prometheus.AspNetCore.csproj

@@ -42,4 +42,3 @@
   </ItemGroup>
 
 </Project>
-

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

@@ -242,14 +242,14 @@ private ExportResult OnCollect(in Batch<Metric> metrics)
 
                                 break;
                             }
-                            catch (IndexOutOfRangeException)
+                            catch (Exception ex) when (ex is IndexOutOfRangeException or ArgumentException)
                             {
                                 if (!IncreaseBufferSize(ref buffer))
                                 {
                                     // 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
+                                    // 2. we got an ArgumentException/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;
@@ -280,7 +280,7 @@ private ExportResult OnCollect(in Batch<Metric> metrics)
 
                         break;
                     }
-                    catch (IndexOutOfRangeException)
+                    catch (Exception ex) when (ex is IndexOutOfRangeException or ArgumentException)
                     {
                         if (!IncreaseBufferSize(ref buffer))
                         {
@@ -297,7 +297,7 @@ private ExportResult OnCollect(in Batch<Metric> metrics)
                     cursor = PrometheusSerializer.WriteEof(buffer, cursor);
                     break;
                 }
-                catch (IndexOutOfRangeException)
+                catch (Exception ex) when (ex is IndexOutOfRangeException or ArgumentException)
                 {
                     if (!IncreaseBufferSize(ref buffer))
                     {
@@ -346,7 +346,7 @@ private int WriteTargetInfo(ref byte[] buffer)
 
                     break;
                 }
-                catch (IndexOutOfRangeException)
+                catch (Exception ex) when (ex is IndexOutOfRangeException or ArgumentException)
                 {
                     if (!IncreaseBufferSize(ref buffer))
                     {

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

@@ -62,6 +62,22 @@ public PrometheusMetric(string name, string unit, PrometheusType type, bool disa
         this.OpenMetricsMetadataName = openMetricsMetadataName;
         this.Unit = sanitizedUnit;
         this.Type = type;
+        this.NameBytes = ConvertToAsciiBytes(sanitizedName);
+        this.OpenMetricsNameBytes = ConvertToAsciiBytes(openMetricsName);
+        this.OpenMetricsMetadataNameBytes = ConvertToAsciiBytes(openMetricsMetadataName);
+        this.UnitBytes = sanitizedUnit == null ? null : ConvertToAsciiBytes(sanitizedUnit);
+
+        static byte[] ConvertToAsciiBytes(string value)
+        {
+            var bytes = new byte[value.Length];
+
+            for (var i = 0; i < value.Length; i++)
+            {
+                bytes[i] = unchecked((byte)value[i]);
+            }
+
+            return bytes;
+        }
     }
 
     public string Name { get; }
@@ -74,8 +90,21 @@ public PrometheusMetric(string name, string unit, PrometheusType type, bool disa
 
     public PrometheusType Type { get; }
 
-    public static PrometheusMetric Create(Metric metric, bool disableTotalNameSuffixForCounters)
-        => new(metric.Name, metric.Unit, GetPrometheusType(metric.MetricType), disableTotalNameSuffixForCounters);
+    internal byte[] NameBytes { get; }
+
+    internal byte[] OpenMetricsNameBytes { get; }
+
+    internal byte[] OpenMetricsMetadataNameBytes { get; }
+
+    internal byte[]? UnitBytes { get; }
+
+    internal byte[]? SerializedStaticTags { get; private set; }
+
+    public static PrometheusMetric Create(Metric metric, bool disableTotalNameSuffixForCounters) =>
+        new(metric.Name, metric.Unit, GetPrometheusType(metric.MetricType), disableTotalNameSuffixForCounters)
+        {
+            SerializedStaticTags = PrometheusSerializer.SerializeStaticTags(metric),
+        };
 
     internal static string SanitizeMetricUnit(string metricUnit)
     {