extract java21 module

build.gradle

@@ -337,7 +337,7 @@ subprojects {
 
             check.dependsOn("testModules")
 
-            if (!(project.name in ['micrometer-registry-prometheus', 'micrometer-registry-prometheus-simpleclient', 'micrometer-jakarta9', 'micrometer-java11', 'micrometer-jetty12'])) { // add projects here that do not exist in the previous minor so should be excluded from japicmp
+            if (!(project.name in ['micrometer-registry-prometheus', 'micrometer-registry-prometheus-simpleclient', 'micrometer-jakarta9', 'micrometer-java11', 'micrometer-java21', 'micrometer-jetty12'])) { // add projects here that do not exist in the previous minor so should be excluded from japicmp
                 apply plugin: 'me.champeau.gradle.japicmp'
                 apply plugin: 'de.undercouch.download'
 

micrometer-java21/build.gradle

@@ -0,0 +1,18 @@
+description 'Micrometer core classes that require Java 21'
+
+dependencies {
+    api project(":micrometer-core")
+
+    testImplementation 'org.awaitility:awaitility'
+    testImplementation project(":micrometer-observation-test")
+}
+
+java {
+    targetCompatibility = 21
+}
+
+tasks.withType(JavaCompile).configureEach {
+    sourceCompatibility = JavaVersion.VERSION_21
+    targetCompatibility = JavaVersion.VERSION_21
+    options.release = 21
+}

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/jvm/JvmVirtualThreadEventMetrics.java → micrometer-java21/src/main/java/io/micrometer/java21/instrument/binder/jfr/JfrVirtualThreadEventMetrics.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package io.micrometer.core.instrument.binder.jvm;
+package io.micrometer.java21.instrument.binder.jfr;
 
 import io.micrometer.core.instrument.Counter;
 import io.micrometer.core.instrument.MeterRegistry;
@@ -25,35 +25,46 @@
 import java.io.Closeable;
 import java.io.IOException;
 import java.time.Duration;
+import java.util.Objects;
 
 import static java.util.Collections.emptyList;
 
-public class JvmVirtualThreadEventMetrics implements MeterBinder, Closeable {
+public class JfrVirtualThreadEventMetrics implements MeterBinder, Closeable {
 
-    private static final String PINNED_EVENT = "jdk.VirtualThreadPinned";
+    public static final String PINNED_EVENT = "jdk.VirtualThreadPinned";
 
-    private static final String SUBMIT_FAILED_EVENT = "jdk.VirtualThreadSubmitFailed";
+    public static final String SUBMIT_FAILED_EVENT = "jdk.VirtualThreadSubmitFailed";
+
+    private final RecordingSettings settings;
 
     private final Iterable<Tag> tags;
 
-    private final RecordingStream recordingStream;
+    private boolean started = false;
+
+    private RecordingStream recordingStream;
 
-    public JvmVirtualThreadEventMetrics() {
-        this(emptyList());
+    public JfrVirtualThreadEventMetrics() {
+        this(new RecordingSettings(), emptyList());
     }
 
-    public JvmVirtualThreadEventMetrics(Iterable<Tag> tags) {
-        this.tags = tags;
-        this.recordingStream = new RecordingStream();
+    public JfrVirtualThreadEventMetrics(Iterable<Tag> tags) {
+        this(new RecordingSettings(), tags);
+    }
 
-        recordingStream.enable(PINNED_EVENT);
-        recordingStream.enable(SUBMIT_FAILED_EVENT);
-        recordingStream.setMaxAge(Duration.ofSeconds(5));
-        recordingStream.startAsync();
+    public JfrVirtualThreadEventMetrics(RecordingSettings settings, Iterable<Tag> tags) {
+        this.settings = settings;
+        this.tags = tags;
     }
 
     @Override
     public void bindTo(MeterRegistry registry) {
+        if (started) {
+            return;
+        }
+
+        started = true;
+        recordingStream = createRecordingStream(settings);
+
         final Timer pinnedTimer =
             Timer.builder("jvm.virtual.thread.pinned")
                 .tags(tags)
@@ -70,8 +81,30 @@ public void bindTo(MeterRegistry registry) {
         recordingStream.onEvent(SUBMIT_FAILED_EVENT, event -> submitFailedCounter.increment());
     }
 
+    protected RecordingStream createRecordingStream(RecordingSettings settings) {
+        final RecordingStream recordingStream = new RecordingStream();
+        recordingStream.enable(PINNED_EVENT).withThreshold(settings.pinnedThreshold);
+        recordingStream.enable(SUBMIT_FAILED_EVENT);
+        recordingStream.setMaxAge(settings.maxAge);
+        recordingStream.setMaxSize(settings.maxSize);
+        recordingStream.startAsync();
+        return recordingStream;
+    }
+
     @Override
     public void close() throws IOException {
-        recordingStream.close();
+        if (started) {
+            recordingStream.close();
+        }
+    }
+
+    public record RecordingSettings(Duration maxAge, long maxSize, Duration pinnedThreshold) {
+        public RecordingSettings {
+            Objects.requireNonNull(maxAge, "maxAge parameter must not be null");
+            Objects.requireNonNull(pinnedThreshold, "pinnedThreshold must not be null");
+        }
+        public RecordingSettings() {
+            this(Duration.ofSeconds(5), 10L * 1024 * 1024, Duration.ofMillis(1));
+        }
     }
 }

micrometer-java21/src/test/java/io/micrometer/java21/instrument/binder/jfr/JfrVirtualThreadEventMetricsTests.java

@@ -0,0 +1,58 @@
+package io.micrometer.java21.instrument.binder.jfr;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tags;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.time.Duration;
+
+import static org.awaitility.Awaitility.await;
+
+class JfrVirtualThreadEventMetricsTests {
+
+    private static final Tags USER_TAGS = Tags.of("k", "v");
+
+    private MeterRegistry registry;
+
+    private JfrVirtualThreadEventMetrics jfrMetrics;
+
+    @BeforeEach
+    void setup() {
+        registry = new SimpleMeterRegistry();
+        jfrMetrics = new JfrVirtualThreadEventMetrics(USER_TAGS);
+        jfrMetrics.bindTo(registry);
+    }
+
+    @Test
+    void registerPinnedEvent() throws Exception {
+        Thread.ofVirtual()
+            .name("vt-test")
+            .start(() -> {
+                synchronized (this) {
+                    sleep(Duration.ofMillis(100));
+                }
+            })
+            .join();
+
+        await().atMost(Duration.ofSeconds(2))
+            .until(() -> registry.get("jvm.virtual.thread.pinned").timer().count() == 1);
+    }
+
+    private void sleep(Duration duration) {
+        try {
+            Thread.sleep(duration);
+        }
+        catch (InterruptedException ignored) {
+        }
+    }
+
+    @AfterEach
+    void cleanup() throws IOException {
+        jfrMetrics.close();
+    }
+
+}

settings.gradle

@@ -47,6 +47,7 @@ include 'concurrency-tests'
 include 'micrometer-bom'
 include 'micrometer-jakarta9'
 include 'micrometer-java11'
+include 'micrometer-java21'
 include 'micrometer-jetty11'
 include 'micrometer-jetty12'
 include 'micrometer-osgi-test'