feat(logs): Drop log events once buffer hits hard limit

CHANGELOG.md

@@ -13,6 +13,8 @@
   - For feature flag evaluations tracked on spans:
     - Only 10 evaluations are tracked per span, existing flags are updated but new ones exceeding the limit are ignored
     - Spans do not inherit evaluations from their parent
+- Drop log events once buffer hits hard limit ([#4889](https://github.com/getsentry/sentry-java/pull/4889))
+  - If we have 1000 log events queued up, we drop any new logs coming in to prevent OOM
 - Remove vendored code and upgrade to async profiler 4.2 ([#4856](https://github.com/getsentry/sentry-java/pull/4856))
   - This adds support for JDK 23+
 

sentry/api/sentry.api

@@ -5034,6 +5034,7 @@ public final class io/sentry/logger/LoggerApi : io/sentry/logger/ILoggerApi {
 public final class io/sentry/logger/LoggerBatchProcessor : io/sentry/logger/ILoggerBatchProcessor {
 	public static final field FLUSH_AFTER_MS I
 	public static final field MAX_BATCH_SIZE I
+	public static final field MAX_QUEUE_SIZE I
 	public fun <init> (Lio/sentry/SentryOptions;Lio/sentry/ISentryClient;)V
 	public fun add (Lio/sentry/SentryLogEvent;)V
 	public fun close (Z)V

sentry/src/main/java/io/sentry/logger/LoggerBatchProcessor.java

@@ -1,5 +1,6 @@
 package io.sentry.logger;
 
+import io.sentry.DataCategory;
 import io.sentry.ISentryClient;
 import io.sentry.ISentryExecutorService;
 import io.sentry.ISentryLifecycleToken;
@@ -8,8 +9,10 @@
 import io.sentry.SentryLogEvent;
 import io.sentry.SentryLogEvents;
 import io.sentry.SentryOptions;
+import io.sentry.clientreport.DiscardReason;
 import io.sentry.transport.ReusableCountLatch;
 import io.sentry.util.AutoClosableReentrantLock;
+import io.sentry.util.JsonSerializationUtils;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Queue;
@@ -24,6 +27,7 @@ public final class LoggerBatchProcessor implements ILoggerBatchProcessor {
 
   public static final int FLUSH_AFTER_MS = 5000;
   public static final int MAX_BATCH_SIZE = 100;
+  public static final int MAX_QUEUE_SIZE = 1000;
 
   private final @NotNull SentryOptions options;
   private final @NotNull ISentryClient client;
@@ -46,6 +50,17 @@ public LoggerBatchProcessor(
 
   @Override
   public void add(final @NotNull SentryLogEvent logEvent) {
+    if (pendingCount.getCount() >= MAX_QUEUE_SIZE) {
+      options
+          .getClientReportRecorder()
+          .recordLostEvent(DiscardReason.QUEUE_OVERFLOW, DataCategory.LogItem);
+      final long lostBytes =
+          JsonSerializationUtils.byteSizeOf(options.getSerializer(), options.getLogger(), logEvent);
+      options
+          .getClientReportRecorder()
+          .recordLostEvent(DiscardReason.QUEUE_OVERFLOW, DataCategory.Attachment, lostBytes);
+      return;
+    }
     pendingCount.increment();
     queue.offer(logEvent);
     maybeSchedule(false, false);

sentry/src/test/java/io/sentry/logger/LoggerBatchProcessorTest.kt

@@ -0,0 +1,101 @@
+package io.sentry.logger
+
+import io.sentry.DataCategory
+import io.sentry.ISentryClient
+import io.sentry.SentryLogEvent
+import io.sentry.SentryLogEvents
+import io.sentry.SentryLogLevel
+import io.sentry.SentryNanotimeDate
+import io.sentry.SentryOptions
+import io.sentry.clientreport.ClientReportTestHelper
+import io.sentry.clientreport.DiscardReason
+import io.sentry.clientreport.DiscardedEvent
+import io.sentry.protocol.SentryId
+import io.sentry.test.DeferredExecutorService
+import io.sentry.test.injectForField
+import io.sentry.util.JsonSerializationUtils
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+import org.mockito.kotlin.argumentCaptor
+import org.mockito.kotlin.atLeast
+import org.mockito.kotlin.mock
+import org.mockito.kotlin.verify
+
+class LoggerBatchProcessorTest {
+  @Test
+  fun `drops log events after reaching MAX_QUEUE_SIZE limit`() {
+    // given
+    val mockClient = mock<ISentryClient>()
+    val mockExecutor = DeferredExecutorService()
+    val options = SentryOptions()
+    val processor = LoggerBatchProcessor(options, mockClient)
+    processor.injectForField("executorService", mockExecutor)
+
+    for (i in 1..1001) {
+      val logEvent =
+        SentryLogEvent(SentryId(), SentryNanotimeDate(), "log message $i", SentryLogLevel.INFO)
+      processor.add(logEvent)
+    }
+
+    // run twice since a non full batch would be scheduled at the end
+    mockExecutor.runAll()
+    mockExecutor.runAll()
+
+    // assert that the transport received 1000 log events
+    val captor = argumentCaptor<SentryLogEvents>()
+    verify(mockClient, atLeast(1)).captureBatchedLogEvents(captor.capture())
+
+    val allCapturedEvents = mutableListOf<SentryLogEvent>()
+    captor.allValues.forEach { logEvents -> allCapturedEvents.addAll(logEvents.items) }
+
+    assertEquals(1000, allCapturedEvents.size)
+
+    // assert that log 1001 did not make it but log 1000 did get sent
+    val log1000Found = allCapturedEvents.any { it.body == "log message 1000" }
+    val log1001Found = allCapturedEvents.any { it.body == "log message 1001" }
+
+    assertTrue(log1000Found, "Log 1000 should have been sent")
+    assertFalse(log1001Found, "Log 1001 should not have been sent")
+  }
+
+  @Test
+  fun `records client report when log event is dropped due to queue overflow`() {
+    // given
+    val mockClient = mock<ISentryClient>()
+    val mockExecutor = DeferredExecutorService()
+    val options = SentryOptions()
+    val processor = LoggerBatchProcessor(options, mockClient)
+    processor.injectForField("executorService", mockExecutor)
+
+    // fill the queue to MAX_QUEUE_SIZE
+    for (i in 1..1000) {
+      val logEvent =
+        SentryLogEvent(SentryId(), SentryNanotimeDate(), "log message $i", SentryLogLevel.INFO)
+      processor.add(logEvent)
+    }
+
+    // add one more log event that should be dropped
+    val droppedLogEvent =
+      SentryLogEvent(SentryId(), SentryNanotimeDate(), "dropped log", SentryLogLevel.INFO)
+    processor.add(droppedLogEvent)
+
+    // calculate expected bytes for the dropped log event
+    val expectedBytes =
+      JsonSerializationUtils.byteSizeOf(options.serializer, options.logger, droppedLogEvent)
+
+    // verify that a client report was recorded for the dropped log item and bytes
+    val expectedEvents =
+      mutableListOf(
+        DiscardedEvent(DiscardReason.QUEUE_OVERFLOW.reason, DataCategory.LogItem.category, 1),
+        DiscardedEvent(
+          DiscardReason.QUEUE_OVERFLOW.reason,
+          DataCategory.Attachment.category,
+          expectedBytes,
+        ),
+      )
+
+    ClientReportTestHelper.assertClientReport(options.clientReportRecorder, expectedEvents)
+  }
+}