Collect PerformanceCollectionData only in sampled transactions

CHANGELOG.md

@@ -12,6 +12,8 @@
 ### Improvements
 
 - [ANR] Defer some class availability checks ([#4825](https://github.com/getsentry/sentry-java/pull/4825))
+- Collect PerformanceCollectionData only for sampled transactions ([#4834](https://github.com/getsentry/sentry-java/pull/4834))
+  - **Breaking change**: Transactions with a deferred sampling decision (`sampled == null`) won't be collecting any performance data anymore (CPU, RAM, slow/frozen frames).
 
 ### Dependencies
 

sentry/src/main/java/io/sentry/SentryTracer.java

@@ -77,7 +77,9 @@ public SentryTracer(
     this.name = context.getName();
     this.instrumenter = context.getInstrumenter();
     this.scopes = scopes;
-    this.compositePerformanceCollector = compositePerformanceCollector;
+    // Let's collect performance data (cpu, ram, frames) only when the transaction is sampled
+    this.compositePerformanceCollector =
+        Boolean.TRUE.equals(isSampled()) ? compositePerformanceCollector : null;
     this.transactionNameSource = context.getTransactionNameSource();
     this.transactionOptions = transactionOptions;
 
@@ -90,9 +92,9 @@ public SentryTracer(
     }
 
     // We are currently sending the performance data only in profiles, but we are always sending
-    // performance measurements.
-    if (compositePerformanceCollector != null) {
-      compositePerformanceCollector.start(this);
+    // performance measurements (frames data in spans).
+    if (this.compositePerformanceCollector != null) {
+      this.compositePerformanceCollector.start(this);
     }
 
     if (transactionOptions.getIdleTimeout() != null

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

@@ -4,6 +4,7 @@ import io.sentry.protocol.SentryId
 import io.sentry.protocol.TransactionNameSource
 import io.sentry.protocol.User
 import io.sentry.test.createTestScopes
+import io.sentry.test.getProperty
 import io.sentry.util.thread.IThreadChecker
 import java.time.LocalDateTime
 import java.time.ZoneOffset
@@ -1170,9 +1171,20 @@ class SentryTracerTest {
   }
 
   @Test
-  fun `when transaction is created, but not profiled, compositePerformanceCollector is started anyway`() {
-    val transaction = fixture.getSut()
+  fun `when transaction is created and sampled, but not profiled, compositePerformanceCollector is started anyway`() {
+    val transaction = fixture.getSut(samplingDecision = TracesSamplingDecision(true))
     verify(fixture.compositePerformanceCollector).start(anyOrNull<ITransaction>())
+    assertEquals(
+      fixture.compositePerformanceCollector,
+      transaction.getProperty("compositePerformanceCollector"),
+    )
+  }
+
+  @Test
+  fun `when transaction is created, but not sampled, compositePerformanceCollector is not started nor set`() {
+    val transaction = fixture.getSut(samplingDecision = TracesSamplingDecision(false))
+    verify(fixture.compositePerformanceCollector, never()).start(anyOrNull<ITransaction>())
+    assertNull(transaction.getProperty("compositePerformanceCollector"))
   }
 
   @Test
@@ -1188,15 +1200,15 @@ class SentryTracerTest {
 
   @Test
   fun `when transaction is finished, compositePerformanceCollector is stopped`() {
-    val transaction = fixture.getSut()
+    val transaction = fixture.getSut(samplingDecision = TracesSamplingDecision(true))
     transaction.finish()
     verify(fixture.compositePerformanceCollector)
       .stop(check<ITransaction> { assertEquals(transaction, it) })
   }
 
   @Test
   fun `when a span is started and finished the compositePerformanceCollector gets notified`() {
-    val transaction = fixture.getSut()
+    val transaction = fixture.getSut(samplingDecision = TracesSamplingDecision(true))
 
     val span = transaction.startChild("op.span")
     span.finish()
@@ -1205,6 +1217,17 @@ class SentryTracerTest {
     verify(fixture.compositePerformanceCollector).onSpanFinished(check { assertEquals(span, it) })
   }
 
+  @Test
+  fun `when a span is started and finished the compositePerformanceCollector gets never notified if not sampled`() {
+    val transaction = fixture.getSut(samplingDecision = TracesSamplingDecision(false))
+
+    val span = transaction.startChild("op.span")
+    span.finish()
+
+    verify(fixture.compositePerformanceCollector, never()).onSpanStarted(any())
+    verify(fixture.compositePerformanceCollector, never()).onSpanFinished(any())
+  }
+
   @Test
   fun `changing transaction name without source sets source to custom`() {
     val transaction = fixture.getSut()
@@ -1393,6 +1416,7 @@ class SentryTracerTest {
       }
     val transaction =
       fixture.getSut(
+        samplingDecision = TracesSamplingDecision(true),
         optionsConfiguration = { it.profilesSampleRate = 1.0 },
         performanceCollector = mockPerformanceCollector,
       )