fix: match rate limits by data category not envelope item type

src/Sentry/Internal/BatchProcessor.cs

@@ -67,7 +67,7 @@ internal void Enqueue(TItem item)
             activeBuffer = ReferenceEquals(activeBuffer, _buffer1) ? _buffer2 : _buffer1;
             if (!TryEnqueue(activeBuffer, item))
             {
-                _clientReportRecorder.RecordDiscardedEvent(DiscardReason.Backpressure, DataCategory.Default, 1);
+                _clientReportRecorder.RecordDiscardedEvent(DiscardReason.Backpressure, DiscardCategory, 1);
                 _diagnosticLogger?.LogInfo("{0}-Buffer full ... dropping {0}", item.GetType().Name);
             }
         }
@@ -131,6 +131,11 @@ private void CaptureItems(BatchBuffer<TItem> buffer)
 
     protected abstract void CaptureEnvelope(IHub hub, TItem[] items);
 
+    /// <summary>
+    /// The data category used when recording dropped items as client reports.
+    /// </summary>
+    protected abstract DataCategory DiscardCategory { get; }
+
     private void OnTimeoutExceeded(BatchBuffer<TItem> buffer)
     {
         if (!buffer.IsEmpty)
@@ -158,6 +163,8 @@ protected override void CaptureEnvelope(IHub hub, SentryLog[] items)
     {
         _ = hub.CaptureEnvelope(Envelope.FromLog(new StructuredLog(items)));
     }
+
+    protected override DataCategory DiscardCategory => DataCategory.LogItem;
 }
 
 internal sealed class SentryMetricBatchProcessor : BatchProcessor<SentryMetric>
@@ -171,4 +178,6 @@ protected override void CaptureEnvelope(IHub hub, SentryMetric[] items)
     {
         _ = hub.CaptureEnvelope(Envelope.FromMetric(new TraceMetric(items)));
     }
+
+    protected override DataCategory DiscardCategory => DataCategory.TraceMetric;
 }

src/Sentry/Internal/DataCategory.cs

@@ -2,15 +2,19 @@ namespace Sentry.Internal;
 
 internal readonly struct DataCategory : IEnumeration<DataCategory>
 {
-    // See https://develop.sentry.dev/sdk/rate-limiting/#definitions for list
+    // See https://develop.sentry.dev/sdk/expected-features/rate-limiting/#definitions for list
     public static DataCategory Attachment = new("attachment");
     public static DataCategory Default = new("default");
     public static DataCategory Error = new("error");
     public static DataCategory Feedback = new("feedback");
     public static DataCategory Internal = new("internal");
+    public static DataCategory LogItem = new("log_item");
+    public static DataCategory MetricBucket = new("metric_bucket");
+    public static DataCategory Monitor = new("monitor");
     public static DataCategory Security = new("security");
     public static DataCategory Session = new("session");
     public static DataCategory Span = new("span");
+    public static DataCategory TraceMetric = new("trace_metric");
     public static DataCategory Transaction = new("transaction");
     public static DataCategory Profile = new("profile");
 

src/Sentry/Internal/Http/RateLimitCategory.cs

@@ -10,28 +10,9 @@ internal class RateLimitCategory : IEquatable<RateLimitCategory>
 
     public RateLimitCategory(string name) => Name = name;
 
-    public bool Matches(EnvelopeItem item)
-    {
-        if (IsMatchAll)
-        {
-            return true;
-        }
-
-        var type = item.TryGetType();
-        if (string.IsNullOrWhiteSpace(type))
-        {
-            return false;
-        }
-
-        return type switch
-        {
-            EnvelopeItem.TypeValueMetric =>
-                // Metrics are a bit unique - the envelope item type is `statsd` but the category is `metric_bucket`
-                string.Equals(Name, "metric_bucket", StringComparison.OrdinalIgnoreCase),
-            // For most reporting categories, the envelope item type matches the client report category
-            _ => string.Equals(Name, type, StringComparison.OrdinalIgnoreCase)
-        };
-    }
+    public bool Matches(EnvelopeItem item) =>
+        // Rate limits are keyed by data category (e.g. "error", "monitor", "metric_bucket"), not envelope item type.
+        IsMatchAll || string.Equals(Name, item.DataCategory.ToString(), StringComparison.OrdinalIgnoreCase);
 
     public bool Equals(RateLimitCategory? other)
     {

src/Sentry/Protocol/Envelopes/EnvelopeItem.cs

@@ -51,9 +51,22 @@ public sealed class EnvelopeItem : ISerializable, IDisposable
         TypeValueSession => DataCategory.Session,
         TypeValueAttachment => DataCategory.Attachment,
         TypeValueProfile => DataCategory.Profile,
+        TypeValueLog => DataCategory.LogItem,
+        TypeValueTraceMetric => DataCategory.TraceMetric,
+
+        // The "check_in" item type corresponds to the "monitor" data category
+        TypeValueCheckIn => DataCategory.Monitor,
+
+        // The "statsd" item type corresponds to the "metric_bucket" data category
+        TypeValueMetric => DataCategory.MetricBucket,
+
+        // Client reports are SDK telemetry that Relay never rate-limits, so map them to a data category
+        // ("internal") that never appears in a rate-limit header. This keeps them from being dropped by a
+        // limit for the "default" category (which is what the fallback below would otherwise assign).
+        TypeValueClientReport => DataCategory.Internal,
 
         // Not all envelope item types equate to data categories
-        // Specifically, user_report and client_report just use "default"
+        // Specifically, user_report just uses "default"
         _ => DataCategory.Default
     };
 

test/Sentry.Tests/Internals/BatchProcessorTests.cs

@@ -159,7 +159,7 @@ public async Task Enqueue_Concurrency_CaptureEnvelopes()
         if (_fixture.ClientReportRecorder.GenerateClientReport() is { } clientReport)
         {
             var discardedEvent = Assert.Single(clientReport.DiscardedEvents);
-            Assert.Equal(new DiscardReasonWithCategory(DiscardReason.Backpressure, DataCategory.Default), discardedEvent.Key);
+            Assert.Equal(new DiscardReasonWithCategory(DiscardReason.Backpressure, DataCategory.LogItem), discardedEvent.Key);
 
             droppedLogs = discardedEvent.Value;
             _fixture.ExpectedDiagnosticLogs = discardedEvent.Value;

test/Sentry.Tests/Internals/Http/HttpTransportTests.cs

@@ -289,7 +289,7 @@ public async Task SendEnvelopeAsync_ItemRateLimit_DropsItem(string metricNamespa
         // Arrange
         using var httpHandler = new RecordingHttpMessageHandler(
             new FakeHttpMessageHandler(
-                () => SentryResponses.GetRateLimitResponse($"1234:event, 897:transaction, {metricNamespace}")
+                () => SentryResponses.GetRateLimitResponse($"1234:error, 897:transaction, {metricNamespace}")
             ));
 
         var httpTransport = new HttpTransport(
@@ -369,7 +369,7 @@ public async Task SendEnvelopeAsync_RateLimited_CountsDiscardedEventsCorrectly()
         // Arrange
         using var httpHandler = new RecordingHttpMessageHandler(
             new FakeHttpMessageHandler(
-                () => SentryResponses.GetRateLimitResponse("1234:event, 897:transaction")
+                () => SentryResponses.GetRateLimitResponse("1234:error, 897:transaction")
             ));
 
         var options = new SentryOptions
@@ -485,7 +485,7 @@ public async Task SendEnvelopeAsync_Fails_RestoresDiscardedEventCounts()
 
             // We also expect two new items recorded, due to the forced HTTP failure.
             {DiscardReason.SendError.WithCategory(DataCategory.Error), 1},  // from the event
-            {DiscardReason.SendError.WithCategory(DataCategory.Default), 1} // from the client report
+            {DiscardReason.SendError.WithCategory(DataCategory.Internal), 1} // from the client report
         });
     }
 
@@ -858,7 +858,7 @@ public async Task SendEnvelopeAsync_RateLimited_CallsBackpressureMonitor()
         // Arrange
         using var httpHandler = new RecordingHttpMessageHandler(
             new FakeHttpMessageHandler(
-                () => SentryResponses.GetRateLimitResponse("1234:event, 897:transaction")
+                () => SentryResponses.GetRateLimitResponse("1234:error, 897:transaction")
             ));
 
         using var backpressureMonitor = new BackpressureMonitor(null, _fakeClock, false);

test/Sentry.Tests/Internals/Http/RateLimitCategoryTests.cs

@@ -5,11 +5,16 @@ namespace Sentry.Tests.Internals.Http;
 public class RateLimitCategoryTests
 {
     [Theory]
-    [InlineData("event", EnvelopeItem.TypeValueEvent)]
+    // Rate limits are keyed by data category, which is not always the envelope item type
+    [InlineData("error", EnvelopeItem.TypeValueEvent)]
+    [InlineData("monitor", EnvelopeItem.TypeValueCheckIn)]
+    [InlineData("log_item", EnvelopeItem.TypeValueLog)]
+    [InlineData("trace_metric", EnvelopeItem.TypeValueTraceMetric)]
     [InlineData("metric_bucket", EnvelopeItem.TypeValueMetric)]
     [InlineData("session", EnvelopeItem.TypeValueSession)]
     [InlineData("transaction", EnvelopeItem.TypeValueTransaction)]
     [InlineData("attachment", EnvelopeItem.TypeValueAttachment)]
+    [InlineData("profile", EnvelopeItem.TypeValueProfile)]
     [InlineData("", EnvelopeItem.TypeValueEvent)]
     [InlineData("", EnvelopeItem.TypeValueMetric)]
     [InlineData("", EnvelopeItem.TypeValueSession)]
@@ -31,7 +36,12 @@ public void Matches_IncludedItemType_ShouldMatch(string categoryName, string ite
     }
 
     [Theory]
-    [InlineData("event", EnvelopeItem.TypeValueTransaction)]
+    // The rate limit category is the data category, not the envelope item type: an "event" item is
+    // limited by the "error" category, so the literal item types below must not match.
+    [InlineData("event", EnvelopeItem.TypeValueEvent)]
+    [InlineData("check_in", EnvelopeItem.TypeValueCheckIn)]
+    [InlineData("statsd", EnvelopeItem.TypeValueMetric)]
+    [InlineData("error", EnvelopeItem.TypeValueTransaction)]
     [InlineData("error", EnvelopeItem.TypeValueAttachment)]
     [InlineData("session", EnvelopeItem.TypeValueEvent)]
     [InlineData("metric_bucket", EnvelopeItem.TypeValueSession)]