ref(checkin): Measure check-in durations with Stopwatch (JAVA-576)

All four check-in paths kept a `long startTime = System.nanoTime()` and
subtracted it in a finally block: CheckInUtils and the SentryCheckInAdvice in
sentry-spring, sentry-spring-jakarta and sentry-spring-7. They now share one
Stopwatch, which takes its clock from the options.

Inert on every path that ships. The options hand the check-in path a
JavaMonotonicTicker, whose tickNanos() is System.nanoTime(), so the serialized
duration is unchanged to the bit. A new test brackets a tick between two
nanoTime readings, pinning the source rather than merely the resolution.

SentryAndroidOptions does override the ticker with a boottime one, but nothing
reaches it from here: check-ins have no Android integration -- no WorkManager,
JobScheduler or AlarmManager wrapper, no manifest option, no Android docs.
Measuring a check-in across device sleep is a change for the next major.

An uninitialized SDK still reaches a clock: NoOpScopes.getOptions() hands back
empty options, whose ticker is the JVM one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: runningcode

sentry-spring-7/src/main/java/io/sentry/spring7/checkin/SentryCheckInAdvice.java

@@ -9,6 +9,7 @@
 import io.sentry.ScopesAdapter;
 import io.sentry.SentryLevel;
 import io.sentry.protocol.SentryId;
+import io.sentry.time.Stopwatch;
 import io.sentry.util.Objects;
 import io.sentry.util.TracingUtils;
 import java.lang.reflect.Method;
@@ -91,7 +92,8 @@ public Object invoke(final @NotNull MethodInvocation invocation) throws Throwabl
       TracingUtils.startNewTrace(scopes);
 
       @Nullable SentryId checkInId = null;
-      final long startTime = System.nanoTime();
+      final @NotNull Stopwatch stopwatch =
+          Stopwatch.started(scopes.getOptions().getMonotonicTicker());
       boolean didError = false;
 
       try {
@@ -105,7 +107,7 @@ public Object invoke(final @NotNull MethodInvocation invocation) throws Throwabl
       } finally {
         final @NotNull CheckInStatus status = didError ? CheckInStatus.ERROR : CheckInStatus.OK;
         CheckIn checkIn = new CheckIn(checkInId, monitorSlug, status);
-        checkIn.setDuration(DateUtils.nanosToSeconds(System.nanoTime() - startTime));
+        checkIn.setDuration(DateUtils.nanosToSeconds(stopwatch.elapsedNanos()));
         scopes.captureCheckIn(checkIn);
       }
     }

sentry-spring-jakarta/src/main/java/io/sentry/spring/jakarta/checkin/SentryCheckInAdvice.java

@@ -9,6 +9,7 @@
 import io.sentry.ScopesAdapter;
 import io.sentry.SentryLevel;
 import io.sentry.protocol.SentryId;
+import io.sentry.time.Stopwatch;
 import io.sentry.util.Objects;
 import io.sentry.util.TracingUtils;
 import java.lang.reflect.Method;
@@ -91,7 +92,8 @@ public Object invoke(final @NotNull MethodInvocation invocation) throws Throwabl
       TracingUtils.startNewTrace(scopes);
 
       @Nullable SentryId checkInId = null;
-      final long startTime = System.nanoTime();
+      final @NotNull Stopwatch stopwatch =
+          Stopwatch.started(scopes.getOptions().getMonotonicTicker());
       boolean didError = false;
 
       try {
@@ -105,7 +107,7 @@ public Object invoke(final @NotNull MethodInvocation invocation) throws Throwabl
       } finally {
         final @NotNull CheckInStatus status = didError ? CheckInStatus.ERROR : CheckInStatus.OK;
         CheckIn checkIn = new CheckIn(checkInId, monitorSlug, status);
-        checkIn.setDuration(DateUtils.nanosToSeconds(System.nanoTime() - startTime));
+        checkIn.setDuration(DateUtils.nanosToSeconds(stopwatch.elapsedNanos()));
         scopes.captureCheckIn(checkIn);
       }
     }

sentry-spring/src/main/java/io/sentry/spring/checkin/SentryCheckInAdvice.java

@@ -9,6 +9,7 @@
 import io.sentry.ScopesAdapter;
 import io.sentry.SentryLevel;
 import io.sentry.protocol.SentryId;
+import io.sentry.time.Stopwatch;
 import io.sentry.util.Objects;
 import io.sentry.util.TracingUtils;
 import java.lang.reflect.Method;
@@ -94,7 +95,8 @@ public Object invoke(final @NotNull MethodInvocation invocation) throws Throwabl
       TracingUtils.startNewTrace(scopes);
 
       @Nullable SentryId checkInId = null;
-      final long startTime = System.nanoTime();
+      final @NotNull Stopwatch stopwatch =
+          Stopwatch.started(scopes.getOptions().getMonotonicTicker());
       boolean didError = false;
 
       try {
@@ -108,7 +110,7 @@ public Object invoke(final @NotNull MethodInvocation invocation) throws Throwabl
       } finally {
         final @NotNull CheckInStatus status = didError ? CheckInStatus.ERROR : CheckInStatus.OK;
         CheckIn checkIn = new CheckIn(checkInId, monitorSlug, status);
-        checkIn.setDuration(DateUtils.nanosToSeconds(System.nanoTime() - startTime));
+        checkIn.setDuration(DateUtils.nanosToSeconds(stopwatch.elapsedNanos()));
         scopes.captureCheckIn(checkIn);
       }
     }

sentry/src/main/java/io/sentry/util/CheckInUtils.java

@@ -9,6 +9,7 @@
 import io.sentry.MonitorConfig;
 import io.sentry.Sentry;
 import io.sentry.protocol.SentryId;
+import io.sentry.time.Stopwatch;
 import java.util.List;
 import java.util.concurrent.Callable;
 import org.jetbrains.annotations.ApiStatus;
@@ -37,7 +38,8 @@ public static <U> U withCheckIn(
     try (final @NotNull ISentryLifecycleToken ignored =
             Sentry.forkedScopes("CheckInUtils").makeCurrent()) {
       final @NotNull IScopes scopes = Sentry.getCurrentScopes();
-      final long startTime = System.nanoTime();
+      final @NotNull Stopwatch stopwatch =
+          Stopwatch.started(scopes.getOptions().getMonotonicTicker());
       boolean didError = false;
 
       TracingUtils.startNewTrace(scopes);
@@ -61,7 +63,7 @@ public static <U> U withCheckIn(
         if (environment != null) {
           checkIn.setEnvironment(environment);
         }
-        checkIn.setDuration(DateUtils.nanosToSeconds(System.nanoTime() - startTime));
+        checkIn.setDuration(DateUtils.nanosToSeconds(stopwatch.elapsedNanos()));
         scopes.captureCheckIn(checkIn);
       }
     }

sentry/src/test/java/io/sentry/util/CheckInUtilsTest.kt

@@ -1,5 +1,6 @@
 package io.sentry.util
 
+import com.google.common.truth.Truth.assertThat
 import io.sentry.CheckInStatus
 import io.sentry.FilterString
 import io.sentry.IScopes
@@ -143,6 +144,7 @@ class CheckInUtilsTest {
       sentry.`when`<Any> { Sentry.forkedScopes(any()) }.then { scopes.forkedScopes("test") }
       whenever(scopes.forkedScopes(any())).thenReturn(scopes)
       whenever(scopes.makeCurrent()).thenReturn(lifecycleToken)
+      whenever(scopes.options).thenReturn(SentryOptions())
 
       try {
         CheckInUtils.withCheckIn("monitor-1") { throw RuntimeException("thrown on purpose") }
@@ -312,4 +314,19 @@ class CheckInUtilsTest {
       assertEquals("America/Los_Angeles", monitorConfig.timezone)
     }
   }
+
+  @Test
+  fun `resolves a ticker that ticks on System nanoTime`() {
+    // The clock the check-in path reads. Bracketing a tick between two System.nanoTime() readings
+    // pins the source, not just the resolution: a ticker on any other monotonic source reports a
+    // different epoch and would fall outside the bracket.
+    val ticker = SentryOptions().monotonicTicker
+
+    val before = System.nanoTime()
+    val tick = ticker.tickNanos()
+    val after = System.nanoTime()
+
+    assertThat(tick).isAtLeast(before)
+    assertThat(tick).isAtMost(after)
+  }
 }