remove metrics from MeterRegistry when shutting down InstrumentedQueu…

…edThreadPool

fixes micrometer-metrics#4000

micrometer-core/src/main/java/io/micrometer/core/instrument/binder/jetty/InstrumentedQueuedThreadPool.java

@@ -15,11 +15,15 @@
  */
 package io.micrometer.core.instrument.binder.jetty;
 
+import io.micrometer.core.instrument.Meter;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Tag;
 import org.eclipse.jetty.util.thread.QueuedThreadPool;
 
+import java.util.HashSet;
+import java.util.Set;
 import java.util.concurrent.BlockingQueue;
+import java.util.stream.Stream;
 
 /**
  * A {@link QueuedThreadPool} that binds metrics about the Jetty server thread pool. This
@@ -116,4 +120,18 @@ protected void doStart() throws Exception {
         threadPoolMetrics.bindTo(registry);
     }
 
+    @Override
+    protected void doStop() throws Exception {
+        Set<Tag> tagSet = new HashSet<>();
+        tags.forEach(tagSet::add);
+        Stream
+            .of("jetty.threads.config.min", "jetty.threads.config.max", "jetty.threads.busy", "jetty.threads.jobs",
+                    "jetty.threads.current", "jetty.threads.idle")
+            .flatMap(name -> registry.find(name).meters().stream())
+            .map(Meter::getId)
+            .filter(id -> new HashSet<>(id.getTags()).containsAll(tagSet))
+            .forEach(registry::remove);
+        super.doStop();
+    }
+
 }

micrometer-core/src/test/java/io/micrometer/core/instrument/binder/jetty/InstrumentedQueuedThreadPoolTest.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright 2019 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.binder.jetty;
+
+import io.micrometer.core.instrument.Gauge;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tag;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import org.assertj.core.api.ListAssert;
+import org.eclipse.jetty.util.thread.QueuedThreadPool;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class InstrumentedQueuedThreadPoolTest {
+
+    @Test
+    void test_metrics() throws Exception {
+        MeterRegistry meterRegistry = new SimpleMeterRegistry();
+        QueuedThreadPool instance = new InstrumentedQueuedThreadPool(meterRegistry,
+                Collections.singletonList(Tag.of("pool", "1")));
+
+        instance.start();
+
+        assertThatMetricsExist(meterRegistry);
+
+        Gauge jobsGauge = meterRegistry.find("jetty.threads.jobs").gauge();
+
+        assertThat(jobsGauge.getId().getTags()).as("ensure metrics have thread pool tag").contains(Tag.of("pool", "1"));
+
+        instance.stop();
+
+        assertThatMetricsDontExist(meterRegistry);
+    }
+
+    @Test
+    void test_multiple_pools() throws Exception {
+        MeterRegistry meterRegistry = new SimpleMeterRegistry();
+        QueuedThreadPool pool1 = new InstrumentedQueuedThreadPool(meterRegistry,
+                Collections.singletonList(Tag.of("pool", "1")));
+
+        QueuedThreadPool pool2 = new InstrumentedQueuedThreadPool(meterRegistry,
+                Collections.singletonList(Tag.of("pool", "2")));
+
+        pool1.start();
+        pool2.start();
+
+        assertThatMetricsExist(meterRegistry);
+
+        assertThat(meterRegistry.find("jetty.threads.jobs").tag("pool", "1").gauge()).as("pool 1 gauge exists")
+            .isNotNull();
+        assertThat(meterRegistry.find("jetty.threads.jobs").tag("pool", "2").gauge()).as("pool 2 gauge exists")
+            .isNotNull();
+
+        pool1.stop();
+
+        assertThat(meterRegistry.find("jetty.threads.jobs").tag("pool", "1").gauge())
+            .as("pool 1 gauge no longer exists")
+            .isNull();
+        assertThat(meterRegistry.find("jetty.threads.jobs").tag("pool", "2").gauge()).as("pool 2 gauge exists")
+            .isNotNull();
+
+        pool2.stop();
+
+        assertThatMetricsDontExist(meterRegistry);
+    }
+
+    private void assertThatMetricsExist(MeterRegistry meterRegistry) {
+        assertThatMetrics(meterRegistry, (l, a) -> a.containsAll(l));
+    }
+
+    private void assertThatMetricsDontExist(MeterRegistry meterRegistry) {
+        assertThatMetrics(meterRegistry, (l, a) -> a.doesNotContainAnyElementsOf(l));
+    }
+
+    private void assertThatMetrics(MeterRegistry meterRegistry,
+            BiFunction<Iterable<String>, ListAssert<String>, ListAssert<String>> assertFunction) {
+        assertFunction.apply(
+                Arrays.asList("jetty.threads.jobs", "jetty.threads.busy", "jetty.threads.idle",
+                        "jetty.threads.config.max", "jetty.threads.config.min", "jetty.threads.current"),
+                assertThat(
+                        meterRegistry.getMeters().stream().map(m -> m.getId().getName()).collect(Collectors.toList())));
+    }
+
+}