Create timer in TransactionPerformanceCollector lazily (#2478)

Author: adinauer

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Fixes
+
+- Create timer in `TransactionPerformanceCollector` lazily ([#2478](https://github.com/getsentry/sentry-java/pull/2478))
+
 ## 6.12.0
 
 ### Features

sentry/src/main/java/io/sentry/TransactionPerformanceCollector.java

@@ -18,7 +18,7 @@ public final class TransactionPerformanceCollector {
   private static final long TRANSACTION_COLLECTION_INTERVAL_MILLIS = 100;
   private static final long TRANSACTION_COLLECTION_TIMEOUT_MILLIS = 30000;
   private final @NotNull Object timerLock = new Object();
-  private volatile @NotNull Timer timer = new Timer();
+  private volatile @Nullable Timer timer = null;
   private final @NotNull Map<String, ArrayList<MemoryCollectionData>> memoryMap =
       new ConcurrentHashMap<>();
   private @Nullable IMemoryCollector memoryCollector = null;
@@ -60,6 +60,9 @@ public void start(final @NotNull ITransaction transaction) {
     }
     if (!isStarted.getAndSet(true)) {
       synchronized (timerLock) {
+        if (timer == null) {
+          timer = new Timer(true);
+        }
         timer.scheduleAtFixedRate(
             new TimerTask() {
               @Override
@@ -87,8 +90,10 @@ public void run() {
     synchronized (timerLock) {
       List<MemoryCollectionData> memoryData = memoryMap.remove(transaction.getEventId().toString());
       if (memoryMap.isEmpty() && isStarted.getAndSet(false)) {
-        timer.cancel();
-        timer = new Timer();
+        if (timer != null) {
+          timer.cancel();
+          timer = null;
+        }
       }
       return memoryData;
     }

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

@@ -32,7 +32,7 @@ class TransactionPerformanceCollectorTest {
         lateinit var transaction2: ITransaction
         val hub: IHub = mock()
         val options = SentryOptions()
-        lateinit var mockTimer: Timer
+        var mockTimer: Timer? = null
         var lastScheduledRunnable: Runnable? = null
 
         val mockExecutorService = object : ISentryExecutorService {
@@ -56,7 +56,7 @@ class TransactionPerformanceCollectorTest {
             transaction1 = SentryTracer(TransactionContext("", ""), hub)
             transaction2 = SentryTracer(TransactionContext("", ""), hub)
             val collector = TransactionPerformanceCollector(options)
-            val timer: Timer = collector.getProperty("timer")
+            val timer: Timer? = collector.getProperty("timer") ?: Timer(true)
             mockTimer = spy(timer)
             collector.injectForField("timer", mockTimer)
             return collector
@@ -77,31 +77,31 @@ class TransactionPerformanceCollectorTest {
         val collector = fixture.getSut(NoOpMemoryCollector.getInstance())
         assertIs<NoOpMemoryCollector>(fixture.options.memoryCollector)
         collector.start(fixture.transaction1)
-        verify(fixture.mockTimer, never()).scheduleAtFixedRate(any(), any<Long>(), any())
+        verify(fixture.mockTimer, never())!!.scheduleAtFixedRate(any(), any<Long>(), any())
     }
 
     @Test
     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)!!.scheduleAtFixedRate(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).cancel()
+        verify(fixture.mockTimer)!!.scheduleAtFixedRate(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()).cancel()
+        verify(fixture.mockTimer, never())!!.scheduleAtFixedRate(any(), any<Long>(), eq(100))
+        verify(fixture.mockTimer, never())!!.cancel()
         assertNull(data)
     }
 
@@ -115,11 +115,11 @@ class TransactionPerformanceCollectorTest {
 
         val data1 = collector.stop(fixture.transaction1)
         // There is still a transaction running: the timer shouldn't stop now
-        verify(fixture.mockTimer, never()).cancel()
+        verify(fixture.mockTimer, never())!!.cancel()
 
         val data2 = collector.stop(fixture.transaction2)
         // There are no more transactions running: the time should stop now
-        verify(fixture.mockTimer).cancel()
+        verify(fixture.mockTimer)!!.cancel()
 
         // The data returned by the collector is not empty
         assertFalse(data1!!.isEmpty())
@@ -132,11 +132,11 @@ class TransactionPerformanceCollectorTest {
         collector.start(fixture.transaction1)
         // Let's sleep to make the collector get values
         Thread.sleep(200)
-        verify(fixture.mockTimer, never()).cancel()
+        verify(fixture.mockTimer, never())!!.cancel()
 
         // Let the timeout job stop the collector
         fixture.lastScheduledRunnable?.run()
-        verify(fixture.mockTimer).cancel()
+        verify(fixture.mockTimer)!!.cancel()
 
         // Data is returned even after the collector times out
         val data1 = collector.stop(fixture.transaction1)