perf(core): Use fixed-delay scheduling for performance collector (JAVA-555) (#5524)

* perf(core): Use fixed-delay scheduling for performance collector

Switch the transaction collection timer from scheduleAtFixedRate to
schedule. Fixed-rate scheduling fires rapid catch-up executions after a
delay or GC pause, which the old code guarded against with a 10ms skip
check. Fixed-delay scheduling spaces each collection 100ms after the
previous one finishes, so the catch-up bursts cannot happen and the
guard, its timestamp field, and the stale comment are no longer needed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* changelog

* test(core): Verify schedule instead of scheduleAtFixedRate

The performance collector now uses fixed-delay scheduling, so the timer
verifications assert schedule(...) rather than scheduleAtFixedRate(...).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* changelog

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: runningcode

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Reduce unboxing in `DateUtils.nanosToDate` ([#5523](https://github.com/getsentry/sentry-java/pull/5523))
 
+### Fixes
+
+- Fix performance collector scheduling many tasks in a row ([#5524](https://github.com/getsentry/sentry-java/pull/5524))
+
 ## 8.43.2
 
 ### Improvements

sentry/src/main/java/io/sentry/DefaultCompositePerformanceCollector.java

@@ -27,7 +27,6 @@ public final class DefaultCompositePerformanceCollector implements CompositePerf
 
   private final @NotNull SentryOptions options;
   private final @NotNull AtomicBoolean isStarted = new AtomicBoolean(false);
-  private long lastCollectionTimestamp = 0;
 
   public DefaultCompositePerformanceCollector(final @NotNull SentryOptions options) {
     this.options = Objects.requireNonNull(options, "The options object is required.");
@@ -112,16 +111,8 @@ public void run() {
             new TimerTask() {
               @Override
               public void run() {
-                long now = System.currentTimeMillis();
-                // The timer is scheduled to run every 100ms on average. In case it takes longer,
-                // subsequent tasks are executed more quickly. If two tasks are scheduled to run in
-                // less than 10ms, the measurement that we collect is not meaningful, so we skip it
-                if (now - lastCollectionTimestamp <= 10) {
-                  return;
-                }
                 timedOutTransactions.clear();
 
-                lastCollectionTimestamp = now;
                 final @NotNull PerformanceCollectionData tempData =
                     new PerformanceCollectionData(options.getDateProvider().now().nanoTimestamp());
 
@@ -147,7 +138,7 @@ public void run() {
                 }
               }
             };
-        timer.scheduleAtFixedRate(
+        timer.schedule(
             timerTask,
             TRANSACTION_COLLECTION_INTERVAL_MILLIS,
             TRANSACTION_COLLECTION_INTERVAL_MILLIS);

sentry/src/test/java/io/sentry/DefaultCompositePerformanceCollectorTest.kt

@@ -86,7 +86,7 @@ class DefaultCompositePerformanceCollectorTest {
     val collector = fixture.getSut(null, null)
     assertTrue(fixture.options.performanceCollectors.isEmpty())
     collector.start(fixture.transaction1)
-    verify(fixture.mockTimer, never())!!.scheduleAtFixedRate(any(), any<Long>(), any())
+    verify(fixture.mockTimer, never())!!.schedule(any(), any<Long>(), any())
   }
 
   @Test
@@ -104,22 +104,22 @@ class DefaultCompositePerformanceCollectorTest {
   fun `when start, timer is scheduled every 100 milliseconds`() {
     val collector = fixture.getSut()
     collector.start(fixture.transaction1)
-    verify(fixture.mockTimer)!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+    verify(fixture.mockTimer)!!.schedule(any(), any<Long>(), eq(100))
   }
 
   @Test
   fun `when start with a string, timer is scheduled every 100 milliseconds`() {
     val collector = fixture.getSut()
     collector.start(fixture.id1)
-    verify(fixture.mockTimer)!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+    verify(fixture.mockTimer)!!.schedule(any(), any<Long>(), eq(100))
   }
 
   @Test
   fun `when stop, timer is stopped`() {
     val collector = fixture.getSut()
     collector.start(fixture.transaction1)
     collector.stop(fixture.transaction1)
-    verify(fixture.mockTimer)!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+    verify(fixture.mockTimer)!!.schedule(any(), any<Long>(), eq(100))
     verify(fixture.mockTimer)!!.cancel()
   }
 
@@ -128,15 +128,15 @@ class DefaultCompositePerformanceCollectorTest {
     val collector = fixture.getSut()
     collector.start(fixture.id1)
     collector.stop(fixture.id1)
-    verify(fixture.mockTimer)!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+    verify(fixture.mockTimer)!!.schedule(any(), any<Long>(), eq(100))
     verify(fixture.mockTimer)!!.cancel()
   }
 
   @Test
   fun `stopping a not collected transaction return null`() {
     val collector = fixture.getSut()
     val data = collector.stop(fixture.transaction1)
-    verify(fixture.mockTimer, never())!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+    verify(fixture.mockTimer, never())!!.schedule(any(), any<Long>(), eq(100))
     verify(fixture.mockTimer, never())!!.cancel()
     assertNull(data)
   }
@@ -145,7 +145,7 @@ class DefaultCompositePerformanceCollectorTest {
   fun `stopping a not collected id return null`() {
     val collector = fixture.getSut()
     val data = collector.stop(fixture.id1)
-    verify(fixture.mockTimer, never())!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+    verify(fixture.mockTimer, never())!!.schedule(any(), any<Long>(), eq(100))
     verify(fixture.mockTimer, never())!!.cancel()
     assertNull(data)
   }
@@ -316,7 +316,7 @@ class DefaultCompositePerformanceCollectorTest {
     collector.close()
 
     // Timer was canceled
-    verify(fixture.mockTimer)!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+    verify(fixture.mockTimer)!!.schedule(any(), any<Long>(), eq(100))
     verify(fixture.mockTimer)!!.cancel()
 
     // Data was cleared