refactor code

Microsoft.Azure.Cosmos/src/CosmosClient.cs

@@ -1438,7 +1438,7 @@ private int DecrementNumberOfActiveClients()
             // In case dispose is called multiple times. Check if at least 1 active client is there
             if (NumberOfActiveClients > 0)
             {
-                CosmosOperationMeter.RemoveInstanceCount(this.Endpoint);
+                CosmosDbOperationMeter.RemoveInstanceCount(this.Endpoint);
 
                 return Interlocked.Decrement(ref NumberOfActiveClients);
             }

Microsoft.Azure.Cosmos/src/DocumentClient.cs

@@ -958,9 +958,9 @@ internal virtual void Initialize(Uri serviceEndpoint,
 
             if (this.cosmosClientTelemetryOptions.IsClientMetricsEnabled)
             {
-                CosmosOperationMeter.Initialize();
+                CosmosDbOperationMeter.Initialize();
 
-                CosmosOperationMeter.AddInstanceCount(this.ServiceEndpoint);
+                CosmosDbOperationMeter.AddInstanceCount(this.ServiceEndpoint);
             }
 
             // Starting ClientTelemetry Job

Microsoft.Azure.Cosmos/src/Resource/ClientContextCore.cs

@@ -539,7 +539,7 @@ private async Task<TResult> RunWithDiagnosticsHelperAsync<TResult>(
                         recorder.Record(response);
 
                         // Records metrics such as request units, latency, and item count for the operation.
-                        CosmosOperationMeter.RecordTelemetry(getOperationName: getOperationName,
+                        CosmosDbOperationMeter.RecordTelemetry(getOperationName: getOperationName,
                                                              accountName: this.client.Endpoint,
                                                              containerName: containerName,
                                                              databaseName: databaseName,
@@ -579,7 +579,7 @@ private async Task<TResult> RunWithDiagnosticsHelperAsync<TResult>(
                     if (openTelemetry != null && ex is CosmosException cosmosException)
                     {
                         // Records telemetry data related to the exception.
-                        CosmosOperationMeter.RecordTelemetry(getOperationName: getOperationName,
+                        CosmosDbOperationMeter.RecordTelemetry(getOperationName: getOperationName,
                                                              accountName: this.client.Endpoint,
                                                              containerName: containerName,
                                                              databaseName: databaseName,

Microsoft.Azure.Cosmos/src/Telemetry/OpenTelemetry/CosmosDbMeterUtil.cs

@@ -0,0 +1,38 @@
+// ------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+// ------------------------------------------------------------
+
+namespace Microsoft.Azure.Cosmos.Telemetry.OpenTelemetry
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.Metrics;
+    using Microsoft.Azure.Cosmos.Core.Trace;
+
+    internal static class CosmosDbMeterUtil
+    {
+        internal static void RecordHistogramMetric<T>(
+            object value,
+            Func<KeyValuePair<string, object>[]> dimensionsFunc,
+            Histogram<T> histogram,
+            Func<object, T> converter = null)
+            where T : struct
+        {
+            if (histogram == null || !histogram.Enabled || value == null)
+            {
+                return;
+            }
+
+            try
+            {
+                T convertedValue = converter != null ? converter(value) : (T)value;
+                histogram.Record(convertedValue, dimensionsFunc());
+            }
+            catch (Exception ex)
+            {
+                DefaultTrace.TraceWarning($"Failed to record metric. {ex.StackTrace}");
+            }
+        }
+
+    }
+}

Microsoft.Azure.Cosmos/src/Telemetry/OpenTelemetry/CosmosDbOperationMeter.cs

@@ -0,0 +1,158 @@
+// ------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+// ------------------------------------------------------------
+
+namespace Microsoft.Azure.Cosmos.Telemetry
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.Metrics;
+    using Microsoft.Azure.Cosmos.Core.Trace;
+    using Microsoft.Azure.Cosmos.Telemetry.OpenTelemetry;
+
+    /// <summary>
+    /// CosmosOperationMeter is a utility class responsible for collecting and recording telemetry metrics related to Cosmos DB operations.
+    /// It includes histograms and counters that capture metrics like request latency, request units, item count, and active instances.
+    /// </summary>
+    internal static class CosmosDbOperationMeter
+    {
+        /// <summary>
+        /// Meter instance for capturing various metrics related to Cosmos DB operations.
+        /// </summary>
+        private static readonly Meter OperationMeter = new Meter(CosmosDbClientMetrics.OperationMetrics.MeterName, CosmosDbClientMetrics.OperationMetrics.Version);
+
+        /// <summary>
+        /// Populator Used for Dimension Attributes
+        /// </summary>
+        private static readonly IActivityAttributePopulator DimensionPopulator = TracesStabilityFactory.GetAttributePopulator();
+
+        /// <summary>
+        /// Histogram to record request latency (in seconds) for Cosmos DB operations.
+        /// </summary>
+        private static Histogram<double> RequestLatencyHistogram = null;
+
+        /// <summary>
+        /// Histogram to record request units consumed during Cosmos DB operations.
+        /// </summary>
+        private static Histogram<double> RequestUnitsHistogram = null;
+
+        /// <summary>
+        /// Histogram to record the actual number of items involved in the operation.
+        /// </summary>
+        private static Histogram<int> ActualItemHistogram = null;
+
+        /// <summary>
+        /// UpDownCounter to track the number of active instances interacting with Cosmos DB.
+        /// </summary>
+        private static UpDownCounter<int> ActiveInstanceCounter = null;
+
+        /// <summary>
+        /// Flag to check if metrics is enabled
+        /// </summary>
+        private static bool IsEnabled = false;
+
+        /// <summary>
+        /// Initializes the histograms and counters for capturing Cosmos DB metrics.
+        /// </summary>
+        internal static void Initialize()
+        {
+            // If already initialized, do not initialize again
+            if (IsEnabled)
+            {
+                return;
+            }
+
+            CosmosDbOperationMeter.RequestLatencyHistogram ??= OperationMeter.CreateHistogram<double>(name: CosmosDbClientMetrics.OperationMetrics.Name.Latency,
+                unit: CosmosDbClientMetrics.OperationMetrics.Unit.Sec,
+                description: CosmosDbClientMetrics.OperationMetrics.Description.Latency);
+
+            CosmosDbOperationMeter.RequestUnitsHistogram ??= OperationMeter.CreateHistogram<double>(name: CosmosDbClientMetrics.OperationMetrics.Name.RequestCharge,
+                unit: CosmosDbClientMetrics.OperationMetrics.Unit.RequestUnit,
+                description: CosmosDbClientMetrics.OperationMetrics.Description.RequestCharge);
+
+            CosmosDbOperationMeter.ActualItemHistogram ??= OperationMeter.CreateHistogram<int>(name: CosmosDbClientMetrics.OperationMetrics.Name.RowCount,
+                unit: CosmosDbClientMetrics.OperationMetrics.Unit.Count, 
+                description: CosmosDbClientMetrics.OperationMetrics.Description.RowCount);
+
+            CosmosDbOperationMeter.ActiveInstanceCounter ??= OperationMeter.CreateUpDownCounter<int>(name: CosmosDbClientMetrics.OperationMetrics.Name.ActiveInstances,
+                unit: CosmosDbClientMetrics.OperationMetrics.Unit.Count,
+                description: CosmosDbClientMetrics.OperationMetrics.Description.ActiveInstances);
+
+            IsEnabled = true;
+        }
+
+        /// <summary>
+        /// Records telemetry data for Cosmos DB operations.
+        /// </summary>
+        internal static void RecordTelemetry(
+            Func<string> getOperationName,
+            Uri accountName,
+            string containerName,
+            string databaseName,
+            OpenTelemetryAttributes attributes = null,
+            CosmosException ex = null)
+        {
+            if (!IsEnabled)
+            {
+                return;
+            }
+
+            try
+            {
+                Func<KeyValuePair<string, object>[]> dimensionsFunc = () =>
+                    DimensionPopulator.PopulateOperationMeterDimensions(
+                        getOperationName(), containerName, databaseName, accountName, attributes, ex);
+
+                CosmosDbMeterUtil.RecordHistogramMetric<int>(value: attributes?.ItemCount ?? ex?.Headers?.ItemCount, 
+                    dimensionsFunc, ActualItemHistogram, 
+                    Convert.ToInt32);
+                CosmosDbMeterUtil.RecordHistogramMetric<double>(value: attributes?.RequestCharge ?? ex?.Headers?.RequestCharge, 
+                    dimensionsFunc, RequestUnitsHistogram);
+                CosmosDbMeterUtil.RecordHistogramMetric<double>(value: attributes?.Diagnostics?.GetClientElapsedTime() ?? ex?.Diagnostics?.GetClientElapsedTime(),
+                    dimensionsFunc, RequestLatencyHistogram, 
+                    t => ((TimeSpan)t).TotalSeconds);
+            }
+            catch (Exception exception)
+            {
+                DefaultTrace.TraceWarning($"Failed to record telemetry data. {exception.StackTrace}");
+            }
+        }
+
+        /// <summary>
+        /// Adjusts the count of active Cosmos DB instances.
+        /// </summary>
+        internal static void AdjustInstanceCount(Uri accountEndpoint, int adjustment)
+        {
+            if (!IsEnabled || ActiveInstanceCounter == null || !ActiveInstanceCounter.Enabled)
+            {
+                return;
+            }
+
+            try
+            {
+                KeyValuePair<string, object>[] dimensions = new[]
+                {
+                    new KeyValuePair<string, object>(OpenTelemetryAttributeKeys.DbSystemName, OpenTelemetryCoreRecorder.CosmosDb),
+                    new KeyValuePair<string, object>(OpenTelemetryAttributeKeys.ServerAddress, accountEndpoint.Host),
+                    new KeyValuePair<string, object>(OpenTelemetryAttributeKeys.ServerPort, accountEndpoint.Port)
+                };
+
+                ActiveInstanceCounter.Add(adjustment, dimensions);
+            }
+            catch (Exception ex)
+            {
+                DefaultTrace.TraceWarning($"Failed to adjust instance count. {ex.StackTrace}");
+            }
+        }
+
+        internal static void AddInstanceCount(Uri accountEndpoint)
+        {
+            AdjustInstanceCount(accountEndpoint, 1);
+        }
+
+        internal static void RemoveInstanceCount(Uri accountEndpoint)
+        {
+            AdjustInstanceCount(accountEndpoint, -1);
+        }
+    }
+}