perf(core): Remove executor prewarm

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## Unreleased
+
+### Performance
+
+- Remove executor prewarm during SDK init ([#5681](https://github.com/getsentry/sentry-java/pull/5681))
+  - The single-threaded `SentryExecutorService` queued the prewarm work ahead of the first useful task, so it could only delay init work, never speed it up; the thread and class loading it warmed are paid identically by the first real task submitted right after.
+
 ## 8.47.0
 
 ### Behavioral Changes

sentry-android-core/src/test/java/io/sentry/android/core/AndroidProfilerTest.kt

@@ -81,8 +81,6 @@ class AndroidProfilerTest {
         override fun close(timeoutMillis: Long) {}
 
         override fun isClosed() = false
-
-        override fun prewarm() = Unit
       }
 
     val options =

sentry-android-core/src/test/java/io/sentry/android/core/AndroidTransactionProfilerTest.kt

@@ -89,8 +89,6 @@ class AndroidTransactionProfilerTest {
         override fun close(timeoutMillis: Long) {}
 
         override fun isClosed() = false
-
-        override fun prewarm() = Unit
       }
 
     val options =

sentry-test-support/src/main/kotlin/io/sentry/test/Mocks.kt

@@ -35,8 +35,6 @@ class ImmediateExecutorService : ISentryExecutorService {
   override fun close(timeoutMillis: Long) {}
 
   override fun isClosed(): Boolean = false
-
-  override fun prewarm() = Unit
 }
 
 class DeferredExecutorService : ISentryExecutorService {
@@ -74,8 +72,6 @@ class DeferredExecutorService : ISentryExecutorService {
 
   override fun isClosed(): Boolean = false
 
-  override fun prewarm() = Unit
-
   fun hasScheduledRunnables(): Boolean = scheduledRunnables.isNotEmpty()
 }
 
@@ -90,8 +86,6 @@ class NonOverridableNoOpSentryExecutorService : ISentryExecutorService {
   override fun close(timeoutMillis: Long) {}
 
   override fun isClosed(): Boolean = false
-
-  override fun prewarm() = Unit
 }
 
 fun createSentryClientMock(enabled: Boolean = true) =

sentry/api/sentry.api

@@ -1133,7 +1133,6 @@ public abstract interface class io/sentry/ISentryClient {
 public abstract interface class io/sentry/ISentryExecutorService {
 	public abstract fun close (J)V
 	public abstract fun isClosed ()Z
-	public abstract fun prewarm ()V
 	public abstract fun schedule (Ljava/lang/Runnable;J)Ljava/util/concurrent/Future;
 	public abstract fun submit (Ljava/lang/Runnable;)Ljava/util/concurrent/Future;
 	public abstract fun submit (Ljava/util/concurrent/Callable;)Ljava/util/concurrent/Future;
@@ -1879,7 +1878,6 @@ public final class io/sentry/NoOpSentryExecutorService : io/sentry/ISentryExecut
 	public fun close (J)V
 	public static fun getInstance ()Lio/sentry/ISentryExecutorService;
 	public fun isClosed ()Z
-	public fun prewarm ()V
 	public fun schedule (Ljava/lang/Runnable;J)Ljava/util/concurrent/Future;
 	public fun submit (Ljava/lang/Runnable;)Ljava/util/concurrent/Future;
 	public fun submit (Ljava/util/concurrent/Callable;)Ljava/util/concurrent/Future;
@@ -3181,7 +3179,6 @@ public final class io/sentry/SentryExecutorService : io/sentry/ISentryExecutorSe
 	public fun <init> (Lio/sentry/SentryOptions;)V
 	public fun close (J)V
 	public fun isClosed ()Z
-	public fun prewarm ()V
 	public fun schedule (Ljava/lang/Runnable;J)Ljava/util/concurrent/Future;
 	public fun submit (Ljava/lang/Runnable;)Ljava/util/concurrent/Future;
 	public fun submit (Ljava/util/concurrent/Callable;)Ljava/util/concurrent/Future;

sentry/src/main/java/io/sentry/ISentryExecutorService.java

@@ -45,10 +45,4 @@ Future<?> schedule(final @NotNull Runnable runnable, final long delayMillis)
    * @return If the executorService was previously closed
    */
   boolean isClosed();
-
-  /**
-   * Pre-warms the executor service by increasing the initial queue capacity. SHOULD be called
-   * directly after instantiating this executor service.
-   */
-  void prewarm();
 }

sentry/src/main/java/io/sentry/NoOpSentryExecutorService.java

@@ -38,7 +38,4 @@ public void close(long timeoutMillis) {}
   public boolean isClosed() {
     return false;
   }
-
-  @Override
-  public void prewarm() {}
 }

sentry/src/main/java/io/sentry/Sentry.java

@@ -351,7 +351,6 @@ private static void init(final @NotNull SentryOptions options, final boolean glo
         // to set a new one
         if (options.getExecutorService().isClosed()) {
           options.setExecutorService(new SentryExecutorService(options));
-          options.getExecutorService().prewarm();
         }
 
         // load lazy fields of the options in a separate thread

sentry/src/main/java/io/sentry/SentryExecutorService.java

@@ -16,13 +16,6 @@
 @ApiStatus.Internal
 public final class SentryExecutorService implements ISentryExecutorService {
 
-  /**
-   * ScheduledThreadPoolExecutor grows work queue by 50% each time. With the initial capacity of 16
-   * it will have to resize 4 times to reach 40, which is a decent middle-ground for prewarming.
-   * This will prevent from growing in unexpected areas of the SDK.
-   */
-  private static final int INITIAL_QUEUE_SIZE = 40;
-
   /**
    * By default, the work queue is unbounded so it can grow as much as the memory allows. We want to
    * limit it by 271 which would be x8 times growth from the default initial capacity.
@@ -32,9 +25,6 @@ public final class SentryExecutorService implements ISentryExecutorService {
   private final @NotNull ScheduledThreadPoolExecutor executorService;
   private final @NotNull AutoClosableReentrantLock lock = new AutoClosableReentrantLock();
 
-  @SuppressWarnings("UnnecessaryLambda")
-  private final @NotNull Runnable dummyRunnable = () -> {};
-
   private final @Nullable SentryOptions options;
 
   @TestOnly
@@ -120,35 +110,6 @@ public boolean isClosed() {
     }
   }
 
-  @SuppressWarnings({"FutureReturnValueIgnored"})
-  @Override
-  public void prewarm() {
-    try {
-      executorService.submit(
-          () -> {
-            try {
-              // schedule a bunch of dummy runnables in the future that will never execute to
-              // trigger
-              // queue growth and then purge the queue
-              for (int i = 0; i < INITIAL_QUEUE_SIZE; i++) {
-                final Future<?> future =
-                    executorService.schedule(dummyRunnable, 365L, TimeUnit.DAYS);
-                future.cancel(true);
-              }
-              executorService.purge();
-            } catch (RejectedExecutionException ignored) {
-              // ignore
-            }
-          });
-    } catch (RejectedExecutionException e) {
-      if (options != null) {
-        options
-            .getLogger()
-            .log(SentryLevel.WARNING, "Prewarm task rejected from " + executorService, e);
-      }
-    }
-  }
-
   private static final class SentryExecutorServiceThreadFactory implements ThreadFactory {
     private int cnt;
 

sentry/src/main/java/io/sentry/SentryOptions.java

@@ -678,7 +678,6 @@ public void activate() {
       // SentryExecutorService should be initialized before any
       // SendCachedEventFireAndForgetIntegration
       executorService = new SentryExecutorService(this);
-      executorService.prewarm();
     }
 
     // SpotlightIntegration is loaded via reflection to allow the sentry-spotlight module

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

@@ -1,6 +1,5 @@
 package io.sentry
 
-import io.sentry.test.getProperty
 import java.util.concurrent.BlockingQueue
 import java.util.concurrent.Callable
 import java.util.concurrent.CancellationException
@@ -191,21 +190,6 @@ class SentryExecutorServiceTest {
     verify(executor).schedule(any<Runnable>(), any(), any())
   }
 
-  @Test
-  fun `SentryExecutorService prewarm schedules dummy tasks and clears queue`() {
-    val executor = ScheduledThreadPoolExecutor(1)
-
-    val sentryExecutor = SentryExecutorService(executor, null)
-    sentryExecutor.prewarm()
-
-    Thread.sleep(1000)
-
-    // the internal queue/array should be resized 4 times to 54
-    assertEquals(54, (executor.queue.getProperty("queue") as Array<*>).size)
-    // the queue should be empty
-    assertEquals(0, executor.queue.size)
-  }
-
   @Test
   fun `SentryExecutorService schedules any number of job`() {
     val executor = ScheduledThreadPoolExecutor(1)

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

@@ -778,7 +778,6 @@ class SentryTest {
       it.cacheDirPath = getTempPath()
       it.setLogger(logger)
       it.executorService = SentryExecutorService()
-      it.executorService.prewarm()
       it.executorService.close(0)
       it.isDebug = true
     }