Discard long-lasting auto-generated transactions

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixes
 
+- Discard long-lasting auto-generated transactions (#1903)
 - Unset scope span when finishing idle transaction (#1902)
 - Set max app start duration to 60s (#1899)
 

Sources/Sentry/SentryTracer.m

@@ -31,6 +31,7 @@
  * transaction are allowed to be apart.
  */
 static const NSTimeInterval SENTRY_APP_START_MEASUREMENT_DIFFERENCE = 5.0;
+static const NSTimeInterval SENTRY_AUTO_TRANSACTION_MAX_DURATION = 500.0;
 
 @interface
 SentryTracer ()
@@ -181,6 +182,11 @@ - (BOOL)hasIdleTimeout
     return self.idleTimeout > 0 && self.dispatchQueueWrapper != nil;
 }
 
+- (BOOL)isAutoGeneratedTransaction
+{
+    return self.waitForChildren || [self hasIdleTimeout];
+}
+
 - (void)cancelIdleTimeout
 {
     if ([self hasIdleTimeout]) {
@@ -430,6 +436,21 @@ - (void)finishInternal
     }
 
     SentryTransaction *transaction = [self toTransaction];
+
+    // Prewarming can execute code up to viewDidLoad of a UIViewController, and keep the app in the
+    // background. This can lead to auto-generated transactions lasting for minutes or event hours.
+    // Therefore, we drop transactions lasting longer than SENTRY_AUTO_TRANSACTION_MAX_DURATION.
+    NSTimeInterval transactionDuration = [self.timestamp timeIntervalSinceDate:self.startTimestamp];
+    if ([self isAutoGeneratedTransaction]
+        && transactionDuration >= SENTRY_AUTO_TRANSACTION_MAX_DURATION) {
+        NSString *message =
+            [NSString stringWithFormat:@"Auto generated transaction exceeded the max duration of "
+                                       @"%f seconds. Not capturing transaction.",
+                      SENTRY_AUTO_TRANSACTION_MAX_DURATION];
+        [SentryLog logWithMessage:message andLevel:kSentryLevelInfo];
+        return;
+    }
+
     NSMutableArray<SentryEnvelopeItem *> *additionalEnvelopeItems = [NSMutableArray array];
 #if SENTRY_TARGET_PROFILING_SUPPORTED
     if ([_hub getClient].options.enableProfiling) {
@@ -444,6 +465,7 @@ - (void)finishInternal
         [profilerLock unlock];
     }
 #endif
+
     [_hub captureTransaction:transaction
                       withScope:_hub.scope
         additionalEnvelopeItems:additionalEnvelopeItems];

Tests/SentryTests/Performance/SentryTracerTests.swift

@@ -134,6 +134,49 @@ class SentryTracerTests: XCTestCase {
         XCTAssertEqual(0, fixture.hub.capturedEventsWithScopes.count)
     }
 
+    func testFinish_WaitForAllChildren_ExceedsMaxDuration_NoTransactionCaptured() {
+        let sut = fixture.getSut()
+
+        advanceTime(bySeconds: 500)
+
+        sut.finish()
+
+        assertTransactionNotCaptured(sut)
+    }
+
+    func testFinish_WaitForAllChildren_DoesNotExceedsMaxDuration_TransactionCaptured() {
+        let sut = fixture.getSut()
+
+        advanceTime(bySeconds: 499.9)
+
+        sut.finish()
+
+        assertOneTransactionCaptured(sut)
+    }
+
+    func testFinish_WaitForAllChildren_StartTimeModified_NoTransactionCaptured() {
+        let appStartMeasurement = fixture.getAppStartMeasurement(type: .cold)
+        SentrySDK.setAppStartMeasurement(appStartMeasurement)
+        advanceTime(bySeconds: 1)
+
+        let sut = fixture.getSut()
+        advanceTime(bySeconds: 499)
+
+        sut.finish()
+
+        assertTransactionNotCaptured(sut)
+    }
+
+    func testFinish_IdleTimeout_ExceedsMaxDuration_NoTransactionCaptured() {
+        let sut = fixture.getSut(idleTimeout: fixture.idleTimeout, dispatchQueueWrapper: fixture.dispatchQueue)
+
+        advanceTime(bySeconds: 500)
+
+        sut.finish()
+
+        assertTransactionNotCaptured(sut)
+    }
+
     func testIdleTimeout_NoChildren_TransactionNotCaptured() {
         _ = fixture.getSut(idleTimeout: fixture.idleTimeout, dispatchQueueWrapper: fixture.dispatchQueue)
 
@@ -564,7 +607,7 @@ class SentryTracerTests: XCTestCase {
     func testChangeStartTimeStamp_RemovesFramesMeasurement() {
         let sut = fixture.getSut()
         fixture.displayLinkWrapper.givenFrames(1, 1, 1)
-        sut.startTimestamp = Date(timeIntervalSince1970: 0)
+        sut.startTimestamp = sut.startTimestamp?.addingTimeInterval(-1)
 
         sut.finish()
 
@@ -681,7 +724,6 @@ class SentryTracerTests: XCTestCase {
 
     private func assertTransactionNotCaptured(_ tracer: SentryTracer) {
         fixture.hub.group.wait()
-        XCTAssertFalse(tracer.isFinished)
         XCTAssertEqual(0, fixture.hub.capturedEventsWithScopes.count)
     }
 
@@ -742,8 +784,8 @@ class SentryTracerTests: XCTestCase {
         fixture.hub.group.wait()
 
         XCTAssertEqual(1, fixture.hub.capturedEventsWithScopes.count)
-        let serializedTransaction = fixture.hub.capturedEventsWithScopes.first!.event.serialize()
-        XCTAssertNil(serializedTransaction["measurements"])
+        let serializedTransaction = fixture.hub.capturedEventsWithScopes.first?.event.serialize()
+        XCTAssertNil(serializedTransaction?["measurements"])
     }
 
 }