Make LongTaskTimer creation conditional in DefaultMeterObservationHan…

…dler (#4755)

micrometer-core/src/main/java/io/micrometer/core/instrument/observation/DefaultMeterObservationHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 VMware, Inc.
+ * Copyright 2024 VMware, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,6 +20,7 @@
 import io.micrometer.observation.Observation;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -42,17 +43,39 @@ public class DefaultMeterObservationHandler implements MeterObservationHandler<O
 
     private final MeterRegistry meterRegistry;
 
+    private final boolean shouldCreateLongTaskTimer;
+
+    /**
+     * Creates the handler with the default configuration.
+     * @param meterRegistry the MeterRegistry to use
+     */
     public DefaultMeterObservationHandler(MeterRegistry meterRegistry) {
         this.meterRegistry = meterRegistry;
+        this.shouldCreateLongTaskTimer = true;
+    }
+
+    /**
+     * Creates the handler with the defined Meters to use when the handler processes the
+     * Observations.
+     * @param meterRegistry the MeterRegistry to use
+     * @param metersToIgnore the Meters that should not be created when Observations are
+     * handled
+     */
+    public DefaultMeterObservationHandler(MeterRegistry meterRegistry, IgnoredMeters... metersToIgnore) {
+        this.meterRegistry = meterRegistry;
+        this.shouldCreateLongTaskTimer = Arrays.stream(metersToIgnore)
+            .noneMatch(ignored -> ignored == IgnoredMeters.LONG_TASK_TIMER);
     }
 
     @Override
     public void onStart(Observation.Context context) {
-        LongTaskTimer.Sample longTaskSample = LongTaskTimer.builder(context.getName() + ".active")
-            .tags(createTags(context))
-            .register(meterRegistry)
-            .start();
-        context.put(LongTaskTimer.Sample.class, longTaskSample);
+        if (shouldCreateLongTaskTimer) {
+            LongTaskTimer.Sample longTaskSample = LongTaskTimer.builder(context.getName() + ".active")
+                .tags(createTags(context))
+                .register(meterRegistry)
+                .start();
+            context.put(LongTaskTimer.Sample.class, longTaskSample);
+        }
 
         Timer.Sample sample = Timer.start(meterRegistry);
         context.put(Timer.Sample.class, sample);
@@ -65,8 +88,10 @@ public void onStop(Observation.Context context) {
         Timer.Sample sample = context.getRequired(Timer.Sample.class);
         sample.stop(Timer.builder(context.getName()).tags(tags).register(this.meterRegistry));
 
-        LongTaskTimer.Sample longTaskSample = context.getRequired(LongTaskTimer.Sample.class);
-        longTaskSample.stop();
+        if (shouldCreateLongTaskTimer) {
+            LongTaskTimer.Sample longTaskSample = context.getRequired(LongTaskTimer.Sample.class);
+            longTaskSample.stop();
+        }
     }
 
     @Override
@@ -90,4 +115,10 @@ private List<Tag> createTags(Observation.Context context) {
         return tags;
     }
 
+    public enum IgnoredMeters {
+
+        LONG_TASK_TIMER
+
+    }
+
 }

micrometer-core/src/test/java/io/micrometer/core/instrument/observation/DefaultMeterObservationHandlerTest.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2024 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.core.instrument.observation;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.Observation.Event;
+import io.micrometer.observation.ObservationRegistry;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.net.SocketTimeoutException;
+
+import static io.micrometer.core.instrument.observation.DefaultMeterObservationHandler.IgnoredMeters.LONG_TASK_TIMER;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link DefaultMeterObservationHandler}. Additional tests can be found in
+ * {@code MeterRegistryCompatibilityKit}.
+ *
+ * @author Jonatan Ivanov
+ */
+class DefaultMeterObservationHandlerTest {
+
+    private ObservationRegistry observationRegistry;
+
+    private MeterRegistry meterRegistry;
+
+    @BeforeEach
+    void setUp() {
+        this.meterRegistry = new SimpleMeterRegistry();
+        this.observationRegistry = ObservationRegistry.create();
+        this.observationRegistry.observationConfig()
+            .observationHandler(new DefaultMeterObservationHandler(this.meterRegistry));
+    }
+
+    @Test
+    void shouldCreateAllMetersDuringAnObservationWithoutError() {
+        Observation observation = Observation.createNotStarted("test.observation", observationRegistry)
+            .lowCardinalityKeyValue("low", "1")
+            .highCardinalityKeyValue("high", "2")
+            .start()
+            .event(Event.of("test.event"));
+
+        assertThat(meterRegistry.get("test.observation.active").tags("low", "1").longTaskTimer().activeTasks())
+            .isEqualTo(1);
+
+        observation.stop();
+
+        assertThat(meterRegistry.get("test.observation").tags("low", "1", "error", "none").timer().count())
+            .isEqualTo(1);
+
+        assertThat(meterRegistry.get("test.observation.active").tags("low", "1").longTaskTimer().activeTasks())
+            .isEqualTo(0);
+
+        assertThat(meterRegistry.get("test.observation.test.event").tags("low", "1").counter().count()).isEqualTo(1);
+    }
+
+    @Test
+    void shouldCreateAllMetersDuringAnObservationWithError() {
+        Observation observation = Observation.createNotStarted("test.observation", observationRegistry)
+            .lowCardinalityKeyValue("low", "1")
+            .highCardinalityKeyValue("high", "2")
+            .start()
+            .event(Event.of("test.event"));
+
+        assertThat(meterRegistry.get("test.observation.active").tags("low", "1").longTaskTimer().activeTasks())
+            .isEqualTo(1);
+
+        observation.error(new SocketTimeoutException("simulated")).stop();
+
+        assertThat(meterRegistry.get("test.observation")
+            .tags("low", "1", "error", "SocketTimeoutException")
+            .timer()
+            .count()).isEqualTo(1);
+
+        assertThat(meterRegistry.get("test.observation.active").tags("low", "1").longTaskTimer().activeTasks())
+            .isEqualTo(0);
+
+        assertThat(meterRegistry.get("test.observation.test.event").tags("low", "1").counter().count()).isEqualTo(1);
+    }
+
+    @Test
+    void shouldNotCreateLongTaskTimerIfIgnored() {
+        this.observationRegistry = ObservationRegistry.create();
+        this.observationRegistry.observationConfig()
+            .observationHandler(new DefaultMeterObservationHandler(this.meterRegistry, LONG_TASK_TIMER));
+
+        Observation.createNotStarted("test.observation", observationRegistry)
+            .lowCardinalityKeyValue("low", "1")
+            .highCardinalityKeyValue("high", "2")
+            .start()
+            .event(Event.of("test.event"))
+            .stop();
+
+        assertThat(meterRegistry.get("test.observation").tags("low", "1", "error", "none").timer().count())
+            .isEqualTo(1);
+
+        assertThat(meterRegistry.get("test.observation.test.event").tags("low", "1").counter().count()).isEqualTo(1);
+
+        assertThat(meterRegistry.find("test.observation.active").longTaskTimers()).isEmpty();
+    }
+
+}