Add de-duplication of telemetry logs

tracer/src/Datadog.Trace/Logging/DirectSubmission/Formatting/EventIdHash.cs

@@ -30,13 +30,15 @@ namespace Datadog.Trace.Logging.DirectSubmission.Formatting
     internal static class EventIdHash
     {
         /// <summary>
-        /// Compute a 32-bit hash of the provided <paramref name="messageTemplate"/>. The
+        /// Compute a 32-bit hash of the provided <paramref name="messageTemplate"/>.
+        /// and optionally a <paramref name="stackTrace"/>. The
         /// resulting hash value can be uses as an event id in lieu of transmitting the
         /// full template string.
         /// </summary>
         /// <param name="messageTemplate">A message template.</param>
+        /// <param name="stackTrace">An optional stack trace to consider in the calculation.</param>
         /// <returns>A 32-bit hash of the template.</returns>
-        public static uint Compute(string messageTemplate)
+        public static uint Compute(string messageTemplate, string? stackTrace = null)
         {
             if (messageTemplate == null)
             {
@@ -54,6 +56,16 @@ public static uint Compute(string messageTemplate)
                     hash ^= (hash >> 6);
                 }
 
+                if (stackTrace is not null)
+                {
+                    for (var i = 0; i < stackTrace.Length; ++i)
+                    {
+                        hash += stackTrace[i];
+                        hash += (hash << 10);
+                        hash ^= (hash >> 6);
+                    }
+                }
+
                 hash += (hash << 3);
                 hash ^= (hash >> 11);
                 hash += (hash << 15);

tracer/src/Datadog.Trace/Logging/Internal/RedactedErrorLogSink.cs

@@ -9,7 +9,6 @@
 using Datadog.Trace.ClrProfiler;
 using Datadog.Trace.Telemetry;
 using Datadog.Trace.Telemetry.Collectors;
-using Datadog.Trace.Telemetry.DTOs;
 using Datadog.Trace.Vendors.Serilog.Core;
 using Datadog.Trace.Vendors.Serilog.Events;
 
@@ -33,12 +32,8 @@ public void Emit(LogEvent? logEvent)
         }
 
         // Note: we're using the raw message template here to remove any chance of including customer information
-        var telemetryLog = new LogMessageData(logEvent.MessageTemplate.Text, ToLogLevel(logEvent.Level), logEvent.Timestamp)
-        {
-            StackTrace = logEvent.Exception is { } ex ? ExceptionRedactor.Redact(ex) : null
-        };
-
-        _collector.EnqueueLog(telemetryLog);
+        var stackTrace = logEvent.Exception is { } ex ? ExceptionRedactor.Redact(ex) : null;
+        _collector.EnqueueLog(logEvent.MessageTemplate.Text, ToLogLevel(logEvent.Level), logEvent.Timestamp, stackTrace);
     }
 
     private static TelemetryLogLevel ToLogLevel(LogEventLevel logEventLevel)

tracer/src/Datadog.Trace/Telemetry/Collectors/RedactedErrorLogCollector.cs

@@ -5,9 +5,12 @@
 
 #nullable enable
 
+using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
+using Datadog.Trace.Logging.DirectSubmission.Formatting;
 using Datadog.Trace.Telemetry.DTOs;
 using Datadog.Trace.Util;
 
@@ -26,15 +29,28 @@ internal class RedactedErrorLogCollector
     private TaskCompletionSource<bool> _tcs = new(TaskOptions);
     private bool _isEnabled = true;
 
+    private ConcurrentDictionary<uint, int> _logCounts = new();
+    private ConcurrentDictionary<uint, int> _logCountsReserve = new();
+
     public List<List<LogMessageData>>? GetLogs()
     {
         // This method should only be called in a single-threaded loop
         List<List<LogMessageData>>? batches = null;
         var batchSize = 0;
         List<LogMessageData>? logs = null;
+        var logCounts = Interlocked.Exchange(ref _logCounts, _logCountsReserve)!;
+
         while (_queue.TryDequeue(out var log))
         {
             var logSize = log.GetApproximateSerializationSize();
+            // modify the message to add the final log count
+            var eventId = EventIdHash.Compute(log.Message, log.StackTrace);
+            if (logCounts.TryGetValue(eventId, out var count) && count > 1)
+            {
+                // TODO: Add the count to the message (not yet supported in Telemetry)
+                // log.InstanceCount = count - 1;
+            }
+
             if (batchSize + logSize < MaximumBatchSizeBytes)
             {
                 batchSize += log.GetApproximateSerializationSize();
@@ -62,14 +78,30 @@ internal class RedactedErrorLogCollector
             batches.Add(logs);
         }
 
+        logCounts.Clear();
+        _logCountsReserve = logCounts;
+
         return batches;
     }
 
-    public void EnqueueLog(LogMessageData log)
+    // For testing
+    internal void EnqueueLog(LogMessageData log)
+        => EnqueueLog(log.Message, log.Level, DateTimeOffset.FromUnixTimeSeconds(log.TracerTime), log.StackTrace);
+
+    public void EnqueueLog(string message, TelemetryLogLevel logLevel, DateTimeOffset timestamp, string? stackTrace)
     {
         if (Volatile.Read(ref _isEnabled))
         {
-            _queue.TryEnqueue(log);
+            var eventId = EventIdHash.Compute(message, stackTrace);
+            var logCounts = _logCounts;
+            var newCount = logCounts.AddOrUpdate(eventId, addValue: 1, updateValueFactory: static (_, prev) => prev + 1);
+            if (newCount != 1)
+            {
+                // already have this log, so don't enqueue it again
+                return;
+            }
+
+            _queue.TryEnqueue(new(message, logLevel, timestamp) { StackTrace = stackTrace });
 
             if (_queue.Count > QueueSizeTrigger)
             {