BufferPoolMetricSet support to collect JMX metrics from remote connec…

…tion (alibaba#41)

metrics-core-impl/src/main/java/com/alibaba/metrics/MetricRegistryImpl.java

@@ -65,6 +65,19 @@ public <T extends Metric> T register(String name, T metric) throws IllegalArgume
         return register(MetricName.build(name), metric);
     }
 
+    /**
+     * 〈unRegister all metrics.〉
+     *
+     *  eg:
+     *      When collecting remote machine JVM metrics through the JMX port, May be due to network jitter or
+     *      remote process restart, Need to cancel the previously collected metrics and re-register.
+     *
+     * @date 2019.06.06 14:35:45
+     */
+    public void unRegisterAll() {
+        metrics.clear();
+    }
+
     /**
      * Given a {@link Metric}, registers it under the given name.
      *

metrics-openjdk/src/main/java/com/alibaba/metrics/jvm/BufferPoolMetricSet.java

@@ -25,8 +25,9 @@
 import org.slf4j.LoggerFactory;
 
 import javax.management.JMException;
-import javax.management.MBeanServer;
+import javax.management.MBeanServerConnection;
 import javax.management.ObjectName;
+import java.io.IOException;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
@@ -42,10 +43,10 @@ public class BufferPoolMetricSet implements MetricSet {
     private static final String[] NAMES = { "count", "used", "capacity" };
     private static final String[] POOLS = { "direct", "mapped" };
 
-    private final MBeanServer mBeanServer;
+    private final MBeanServerConnection mBeanServerConnection;
 
-    public BufferPoolMetricSet(MBeanServer mBeanServer) {
-        this.mBeanServer = mBeanServer;
+    public BufferPoolMetricSet(MBeanServerConnection mBeanServerConnection) {
+        this.mBeanServerConnection = mBeanServerConnection;
     }
 
     @Override
@@ -55,14 +56,14 @@ public Map<MetricName, Metric> getMetrics() {
             for (int i = 0; i < ATTRIBUTES.length; i++) {
                 final String attribute = ATTRIBUTES[i];
                 final String name = NAMES[i];
-
                 try {
                     final ObjectName on = new ObjectName("java.nio:type=BufferPool,name=" + pool);
-                    mBeanServer.getMBeanInfo(on);
-                    gauges.put(MetricRegistry.name(pool, name),
-                               new JmxAttributeGauge(mBeanServer, on, attribute));
+                    mBeanServerConnection.getMBeanInfo(on);
+                    gauges.put(MetricRegistry.name(pool, name), new JmxAttributeGauge(mBeanServerConnection, on, attribute));
                 } catch (JMException ignored) {
                     LOGGER.debug("Unable to load buffer pool MBeans, possibly running on Java 6");
+                } catch (IOException ioException) {
+                    LOGGER.debug("Unable to load buffer pool MBeans, an exception occur, cause of", ioException);
                 }
             }
         }

metrics-openjdk/src/test/java/com/alibaba/metrics/jvm/JmxRemoteMetricsTest.java

@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *     http://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 com.alibaba.metrics.jvm;
+
+import com.alibaba.metrics.Gauge;
+import com.alibaba.metrics.MetricName;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Before;
+import org.junit.Test;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import javax.management.MBeanServerConnection;
+import javax.management.ObjectName;
+
+/**
+ * 〈jmx remote metrics test.〉
+ *
+ * @create 2019/6/6
+ */
+public class JmxRemoteMetricsTest {
+    private ObjectName mapped;
+    private final MetricName MAPPED = MetricName.build("mapped");
+    private final MetricName MAPPED_USED = MAPPED.resolve("used");
+
+    /**
+     * You can get the MBeanServerConnection in the following way:
+     *
+     *     Map<String, Object> environment = new HashMap<String, Object>();
+     *     environment.put(JMXConnector.CREDENTIALS, new String[]{USERNAME, PASSWORD});
+     *     JMXServiceURL jmxServiceURL = new JMXServiceURL("service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi");
+     *     MBeanServerConnection mBeanServerConnection = JMXConnectorFactory.connect(jmxServiceURL, environment).getMBeanServerConnection();
+     **/
+    private final MBeanServerConnection mBeanServerConnection = mock(MBeanServerConnection.class);
+
+    @Before
+    public void setUp() throws Exception {
+        this.mapped = new ObjectName("java.nio:type=BufferPool,name=mapped");
+    }
+
+    @Test
+    public void testCollectionRemoteMetrics() throws Exception {
+        BufferPoolMetricSet bufferPoolMetricSet = new BufferPoolMetricSet(mBeanServerConnection);
+        final Gauge gauge = (Gauge) bufferPoolMetricSet.getMetrics().get(MAPPED_USED);
+        when(mBeanServerConnection.getAttribute(mapped, "MemoryUsed")).thenReturn(100);
+        assertThat(gauge.getValue()).isEqualTo(100);
+    }
+}